/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to you under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.calcite.runtime;

import org.apache.calcite.DataContext;
import org.apache.calcite.avatica.util.ByteString;
import org.apache.calcite.avatica.util.DateTimeUtils;
import org.apache.calcite.avatica.util.Spaces;
import org.apache.calcite.avatica.util.TimeUnitRange;
import org.apache.calcite.interpreter.Row;
import org.apache.calcite.linq4j.AbstractEnumerable;
import org.apache.calcite.linq4j.CartesianProductEnumerator;
import org.apache.calcite.linq4j.Enumerable;
import org.apache.calcite.linq4j.Enumerator;
import org.apache.calcite.linq4j.Linq4j;
import org.apache.calcite.linq4j.Ord;
import org.apache.calcite.linq4j.function.Deterministic;
import org.apache.calcite.linq4j.function.Experimental;
import org.apache.calcite.linq4j.function.Function1;
import org.apache.calcite.linq4j.function.NonDeterministic;
import org.apache.calcite.linq4j.tree.Primitive;
import org.apache.calcite.rel.type.TimeFrame;
import org.apache.calcite.rel.type.TimeFrameSet;
import org.apache.calcite.runtime.FlatLists.ComparableList;
import org.apache.calcite.sql.SqlUtil;
import org.apache.calcite.sql.fun.SqlLibraryOperators;
import org.apache.calcite.util.NumberUtil;
import org.apache.calcite.util.TimeWithTimeZoneString;
import org.apache.calcite.util.TimestampWithTimeZoneString;
import org.apache.calcite.util.Unsafe;
import org.apache.calcite.util.Util;
import org.apache.calcite.util.format.FormatElement;
import org.apache.calcite.util.format.FormatModel;
import org.apache.calcite.util.format.FormatModels;

import org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.binary.Base32;
import org.apache.commons.codec.binary.Hex;
import org.apache.commons.codec.digest.DigestUtils;
import org.apache.commons.codec.language.Soundex;
import org.apache.commons.lang.StringEscapeUtils;
import org.apache.commons.text.similarity.LevenshteinDistance;

import com.google.common.base.Splitter;
import com.google.common.base.Strings;
import com.google.common.cache.CacheBuilder;
import com.google.common.cache.CacheLoader;
import com.google.common.cache.LoadingCache;
import com.google.common.collect.ImmutableList;
import com.google.common.util.concurrent.UncheckedExecutionException;

import org.checkerframework.checker.nullness.qual.Nullable;
import org.checkerframework.checker.nullness.qual.PolyNull;

import java.lang.reflect.Field;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.math.MathContext;
import java.math.RoundingMode;
import java.net.URI;
import java.net.URISyntaxException;
import java.nio.ByteBuffer;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.sql.SQLException;
import java.sql.Time;
import java.sql.Timestamp;
import java.text.DateFormat;
import java.text.DecimalFormat;
import java.text.Normalizer;
import java.text.ParsePosition;
import java.text.SimpleDateFormat;
import java.time.Instant;
import java.time.LocalDate;
import java.time.LocalDateTime;
import java.time.LocalTime;
import java.time.OffsetDateTime;
import java.time.ZoneId;
import java.time.ZoneOffset;
import java.time.format.DateTimeFormatter;
import java.time.format.DateTimeFormatterBuilder;
import java.time.format.DateTimeParseException;
import java.time.format.SignStyle;
import java.time.temporal.ChronoField;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Base64;
import java.util.Calendar;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Date;
import java.util.HashMap;
import java.util.HashSet;
import java.util.LinkedHashMap;
import java.util.LinkedHashSet;
import java.util.LinkedList;
import java.util.List;
import java.util.Locale;
import java.util.Map;
import java.util.Objects;
import java.util.Set;
import java.util.TimeZone;
import java.util.concurrent.atomic.AtomicLong;
import java.util.function.BinaryOperator;
import java.util.function.Consumer;
import java.util.function.Function;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

import static org.apache.calcite.config.CalciteSystemProperty.FUNCTION_LEVEL_CACHE_MAX_SIZE;
import static org.apache.calcite.linq4j.Nullness.castNonNull;
import static org.apache.calcite.util.Static.RESOURCE;

import static java.nio.charset.StandardCharsets.UTF_8;
import static java.util.Objects.requireNonNull;

/**
 * Helper methods to implement SQL functions in generated code.
 *
 * <p>Not present: and, or, not (builtin operators are better, because they
 * use lazy evaluation. Implementations do not check for null values; the
 * calling code must do that.
 *
 * <p>Many of the functions do not check for null values. This is intentional.
 * If null arguments are possible, the code-generation framework checks for
 * nulls before calling the functions.
 */
@SuppressWarnings("UnnecessaryUnboxing")
@Deterministic
public class SqlFunctions {
  @SuppressWarnings("unused")
  private static final DecimalFormat DOUBLE_FORMAT =
      NumberUtil.decimalFormat("0.0E0");

  private static final TimeZone LOCAL_TZ = TimeZone.getDefault();

  private static final DateTimeFormatter ROOT_DAY_FORMAT =
      DateTimeFormatter.ofPattern("EEEE", Locale.ROOT);

  private static final DateTimeFormatter ROOT_MONTH_FORMAT =
      DateTimeFormatter.ofPattern("MMMM", Locale.ROOT);

  private static final Soundex SOUNDEX = new Soundex();

  private static final int SOUNDEX_LENGTH = 4;

  private static final LevenshteinDistance LEVENSHTEIN_DISTANCE =
      LevenshteinDistance.getDefaultInstance();

  private static final Pattern FROM_BASE64_REGEXP = Pattern.compile("[\\t\\n\\r\\s]");

  private static final Base32 BASE_32 = new Base32();

  // Some JVMs can't allocate arrays of length Integer.MAX_VALUE; actual max is somewhat smaller.
  // Be conservative and lower this value a little.
  // @see http://hg.openjdk.java.net/jdk8/jdk8/jdk/file/tip/src/share/classes/java/util/ArrayList.java#l229
  // Note: this variable handling is inspired by Apache Spark
  private static final int MAX_ARRAY_LENGTH = Integer.MAX_VALUE - 15;

  private static final Function1<List<Object>, Enumerable<Object>> LIST_AS_ENUMERABLE =
      a0 -> a0 == null ? Linq4j.emptyEnumerable() : Linq4j.asEnumerable(a0);

  @SuppressWarnings("unused")
  private static final Function1<Object[], Enumerable<@Nullable Object[]>> ARRAY_CARTESIAN_PRODUCT =
      lists -> {
        final List<Enumerator<@Nullable Object>> enumerators = new ArrayList<>();
        for (Object list : lists) {
          enumerators.add(Linq4j.enumerator((List) list));
        }
        final Enumerator<List<@Nullable Object>> product = Linq4j.product(enumerators);
        return new AbstractEnumerable<@Nullable Object[]>() {
          @Override public Enumerator<@Nullable Object[]> enumerator() {
            return Linq4j.transform(product, List::toArray);
          }
        };
      };

  /** Holds, for each thread, a map from sequence name to sequence current
   * value.
   *
   * <p>This is a straw man of an implementation whose main goal is to prove
   * that sequences can be parsed, validated and planned. A real application
   * will want persistent values for sequences, shared among threads. */
  private static final ThreadLocal<@Nullable Map<String, AtomicLong>> THREAD_SEQUENCES =
      ThreadLocal.withInitial(HashMap::new);

  private static final Pattern PATTERN_0_STAR_E = Pattern.compile("0*E");

  /** A byte string consisting of a single byte that is the ASCII space
   * character (0x20). */
  private static final ByteString SINGLE_SPACE_BYTE_STRING =
      ByteString.of("20", 16);

  // Date formatter for BigQuery's timestamp literals:
  // https://cloud.google.com/bigquery/docs/reference/standard-sql/lexical#timestamp_literals
  private static final DateTimeFormatter BIG_QUERY_TIMESTAMP_LITERAL_FORMATTER =
      new DateTimeFormatterBuilder()
          // Unlike ISO 8601, BQ only supports years between 1 - 9999,
          // but can support single-digit month and day parts.
          .appendValue(ChronoField.YEAR, 4)
          .appendLiteral('-')
          .appendValue(ChronoField.MONTH_OF_YEAR, 1, 2, SignStyle.NOT_NEGATIVE)
          .appendLiteral('-')
          .appendValue(ChronoField.DAY_OF_MONTH, 1, 2, SignStyle.NOT_NEGATIVE)
          // Everything after the date is optional. Optional sections can be nested.
          .optionalStart()
          // BQ accepts either a literal 'T' or a space to separate the date from the time,
          // so make the 'T' optional but pad with 1 space if it's omitted.
          .padNext(1, ' ')
          .optionalStart()
          .appendLiteral('T')
          .optionalEnd()
          // Unlike ISO 8601, BQ can support single-digit hour, minute, and second parts.
          .appendValue(ChronoField.HOUR_OF_DAY, 1, 2, SignStyle.NOT_NEGATIVE)
          .appendLiteral(':')
          .appendValue(ChronoField.MINUTE_OF_HOUR, 1, 2, SignStyle.NOT_NEGATIVE)
          .appendLiteral(':')
          .appendValue(ChronoField.SECOND_OF_MINUTE, 1, 2, SignStyle.NOT_NEGATIVE)
          // ISO 8601 supports up to nanosecond precision, but BQ only up to microsecond.
          .optionalStart()
          .appendFraction(ChronoField.MICRO_OF_SECOND, 0, 6, true)
          .optionalEnd()
          .optionalStart()
          .parseLenient()
          .appendOffsetId()
          .toFormatter(Locale.ROOT);

  /** Whether the current Java version is 8 (1.8). */
  private static final boolean IS_JDK_8 =
      System.getProperty("java.version").startsWith("1.8");

  private SqlFunctions() {
  }

  /** Internal THROW_UNLESS(condition, message) function.
   *
   * <p>The method is marked {@link NonDeterministic} to prevent the generator
   * from storing its value as a constant. */
  @NonDeterministic
  public static boolean throwUnless(boolean condition, String message) {
    if (!condition) {
      throw new IllegalStateException(message);
    }
    return condition;
  }

  /** SQL TO_BASE64(string) function. */
  public static String toBase64(String string) {
    return toBase64_(string.getBytes(UTF_8));
  }

  /** SQL TO_BASE64(string) function for binary string. */
  public static String toBase64(ByteString string) {
    return toBase64_(string.getBytes());
  }

  private static String toBase64_(byte[] bytes) {
    String base64 = Base64.getEncoder().encodeToString(bytes);
    StringBuilder str = new StringBuilder(base64.length() + base64.length() / 76);
    Splitter.fixedLength(76).split(base64).iterator().forEachRemaining(s -> {
      str.append(s);
      str.append("\n");
    });
    return str.substring(0, str.length() - 1);
  }

  /** SQL FROM_BASE64(string) function. */
  public static @Nullable ByteString fromBase64(String base64) {
    try {
      base64 = FROM_BASE64_REGEXP.matcher(base64).replaceAll("");
      return new ByteString(Base64.getDecoder().decode(base64));
    } catch (IllegalArgumentException e) {
      return null;
    }
  }

  /** SQL TO_BASE32(string) function. */
  public static String toBase32(String string) {
    return toBase32_(string.getBytes(UTF_8));
  }

  /** SQL TO_BASE32(string) function for binary string. */
  public static String toBase32(ByteString string) {
    return toBase32_(string.getBytes());
  }

  private static String toBase32_(byte[] bytes) {
    return BASE_32.encodeToString(bytes);
  }

  /** SQL FROM_BASE32(string) function. */
  public static ByteString fromBase32(String base32) {
    return new ByteString(BASE_32.decode(base32));
  }

  /** SQL FROM_HEX(varchar) function. */
  public static ByteString fromHex(String hex) {
    try {
      return new ByteString(Hex.decodeHex(hex));
    } catch (DecoderException e) {
      throw new IllegalArgumentException(
          String.format(Locale.ROOT, "Failed to decode hex string: %s", hex), e);
    }
  }

  /** SQL TO_HEX(binary) function. */
  public static String toHex(ByteString byteString) {
    return Hex.encodeHexString(byteString.getBytes());
  }

  /** SQL MD5(string) function. */
  public static String md5(String string)  {
    return DigestUtils.md5Hex(string.getBytes(UTF_8));
  }

  /** SQL MD5(string) function for binary string. */
  public static String md5(ByteString string)  {
    return DigestUtils.md5Hex(string.getBytes());
  }

  /** SQL SHA1(string) function. */
  public static String sha1(String string)  {
    return DigestUtils.sha1Hex(string.getBytes(UTF_8));
  }

  /** SQL SHA1(string) function for binary string. */
  public static String sha1(ByteString string)  {
    return DigestUtils.sha1Hex(string.getBytes());
  }

  /** SQL SHA256(string) function. */
  public static String sha256(String string)  {
    return DigestUtils.sha256Hex(string.getBytes(UTF_8));
  }

  /** SQL SHA256(string) function for binary string. */
  public static String sha256(ByteString string)  {
    return DigestUtils.sha256Hex(string.getBytes());
  }

  /** SQL SHA512(string) function. */
  public static String sha512(String string)  {
    return DigestUtils.sha512Hex(string.getBytes(UTF_8));
  }

  /** SQL SHA512(string) function for binary string. */
  public static String sha512(ByteString string)  {
    return DigestUtils.sha512Hex(string.getBytes());
  }

  /** State for {@code REGEXP_CONTAINS}, {@code REGEXP_REPLACE}, {@code RLIKE}.
   *
   * <p>Marked deterministic so that the code generator instantiates one once
   * per query, not once per row. */
  @Deterministic
  public static class RegexFunction {
    /** Cache key. */
    private static class Key extends Ord<String> {
      Key(int flags, String regex) {
        super(flags, regex);
      }

      @SuppressWarnings("MagicConstant")
      Pattern toPattern() {
        return Pattern.compile(e, i);
      }
    }

    private final LoadingCache<Key, Pattern> cache =
        CacheBuilder.newBuilder()
            .maximumSize(FUNCTION_LEVEL_CACHE_MAX_SIZE.value())
            .build(CacheLoader.from(Key::toPattern));

    /** SQL {@code REGEXP_CONTAINS(value, regexp)} function.
     * Throws a runtime exception for invalid regular expressions.*/
    public boolean regexpContains(String value, String regex) {
      final Pattern pattern;
      try {
        // Uses java.util.regex as a standard for regex processing
        // in Calcite instead of RE2 used by BigQuery/GoogleSQL
        pattern = cache.getUnchecked(new Key(0, regex));
      } catch (UncheckedExecutionException e) {
        if (e.getCause() instanceof PatternSyntaxException) {
          throw RESOURCE.invalidInputForRegexpContains(
              stripLineEndings(
                  requireNonNull(e.getCause().getMessage(), "message"))).ex();
        }
        throw e;
      }
      return pattern.matcher(value).find();
    }

    private static String stripLineEndings(String message) {
      return message.replace("\r\n", " ")
          .replace("\n", " ")
          .replace("\r", " ");
    }

    /** SQL {@code REGEXP_REPLACE} function with 3 arguments. */
    public String regexpReplace(String s, String regex,
        String replacement) {
      return regexpReplace(s, regex, replacement, 1, 0, null);
    }

    /** SQL {@code REGEXP_REPLACE} function with 4 arguments. */
    public String regexpReplace(String s, String regex, String replacement,
        int pos) {
      return regexpReplace(s, regex, replacement, pos, 0, null);
    }

    /** SQL {@code REGEXP_REPLACE} function with 5 arguments. */
    public String regexpReplace(String s, String regex, String replacement,
        int pos, int occurrence) {
      return regexpReplace(s, regex, replacement, pos, occurrence, null);
    }

    /** SQL {@code REGEXP_REPLACE} function with 6 arguments. */
    public String regexpReplace(String s, String regex, String replacement,
        int pos, int occurrence, @Nullable String matchType) {
      if (pos < 1 || pos > s.length()) {
        throw RESOURCE.invalidInputForRegexpReplace(Integer.toString(pos)).ex();
      }

      final int flags = matchType == null ? 0 : makeRegexpFlags(matchType);
      final Pattern pattern = cache.getUnchecked(new Key(flags, regex));

      return Unsafe.regexpReplace(s, pattern, replacement, pos, occurrence);
    }

    private static int makeRegexpFlags(String stringFlags) {
      int flags = 0;
      for (int i = 0; i < stringFlags.length(); ++i) {
        switch (stringFlags.charAt(i)) {
        case 'i':
          flags |= Pattern.CASE_INSENSITIVE;
          break;
        case 'c':
          flags &= ~Pattern.CASE_INSENSITIVE;
          break;
        case 'n':
          flags |= Pattern.DOTALL;
          break;
        case 'm':
          flags |= Pattern.MULTILINE;
          break;
        default:
          throw RESOURCE.invalidInputForRegexpReplace(stringFlags).ex();
        }
      }
      return flags;
    }

    /** SQL {@code RLIKE} function. */
    public boolean rlike(String s, String pattern) {
      return cache.getUnchecked(new Key(0, pattern)).matcher(s).find();
    }
  }

  /** SQL {@code LPAD(string, integer, string)} function. */
  public static String lpad(String originalValue, int returnLength,
      String pattern) {
    if (returnLength < 0) {
      throw RESOURCE.illegalNegativePadLength().ex();
    }
    if (pattern.isEmpty()) {
      throw RESOURCE.illegalEmptyPadPattern().ex();
    }
    if (returnLength <= originalValue.length()) {
      return originalValue.substring(0, returnLength);
    }
    int paddingLengthRequired = returnLength - originalValue.length();
    int patternLength = pattern.length();
    final StringBuilder paddedS = new StringBuilder();
    for (int i = 0; i < paddingLengthRequired; i++) {
      char curChar = pattern.charAt(i % patternLength);
      paddedS.append(curChar);
    }
    paddedS.append(originalValue);
    return paddedS.toString();
  }

  /** SQL {@code LPAD(string, integer)} function. */
  public static String lpad(String originalValue, int returnLength) {
    return lpad(originalValue, returnLength, " ");
  }

  /** SQL {@code LPAD(binary, integer, binary)} function. */
  public static ByteString lpad(ByteString originalValue, int returnLength,
      ByteString pattern) {
    if (returnLength < 0) {
      throw RESOURCE.illegalNegativePadLength().ex();
    }
    if (pattern.length() == 0) {
      throw RESOURCE.illegalEmptyPadPattern().ex();
    }
    if (returnLength <= originalValue.length()) {
      return originalValue.substring(0, returnLength);
    }
    int paddingLengthRequired = returnLength - originalValue.length();
    int patternLength = pattern.length();
    byte[] bytes = new byte[returnLength];
    for (int i = 0; i < paddingLengthRequired; i++) {
      byte curByte = pattern.byteAt(i % patternLength);
      bytes[i] = curByte;
    }
    for (int i = paddingLengthRequired; i < returnLength; i++) {
      bytes[i] = originalValue.byteAt(i - paddingLengthRequired);
    }

    return new ByteString(bytes);
  }

  /** SQL {@code LPAD(binary, integer, binary)} function. */
  public static ByteString lpad(ByteString originalValue, int returnLength) {
    // 0x20 is the hexadecimal character for space ' '
    return lpad(originalValue, returnLength, SINGLE_SPACE_BYTE_STRING);
  }

  /** SQL {@code RPAD(string, integer, string)} function. */
  public static String rpad(String originalValue, int returnLength,
      String pattern) {
    if (returnLength < 0) {
      throw RESOURCE.illegalNegativePadLength().ex();
    }
    if (pattern.isEmpty()) {
      throw RESOURCE.illegalEmptyPadPattern().ex();
    }
    if (returnLength <= originalValue.length()) {
      return originalValue.substring(0, returnLength);
    }
    int paddingLengthRequired = returnLength - originalValue.length();
    int patternLength = pattern.length();
    final StringBuilder paddedS = new StringBuilder();
    paddedS.append(originalValue);
    for (int i = 0; i < paddingLengthRequired; i++) {
      char curChar = pattern.charAt(i % patternLength);
      paddedS.append(curChar);
    }
    return paddedS.toString();
  }

  /** SQL {@code RPAD(string, integer)} function. */
  public static String rpad(String originalValue, int returnLength) {
    return rpad(originalValue, returnLength, " ");
  }

  /** SQL {@code RPAD(binary, integer, binary)} function. */
  public static ByteString rpad(ByteString originalValue, int returnLength,
      ByteString pattern) {
    if (returnLength < 0) {
      throw RESOURCE.illegalNegativePadLength().ex();
    }
    if (pattern.length() == 0) {
      throw RESOURCE.illegalEmptyPadPattern().ex();
    }
    int originalLength = originalValue.length();
    if (returnLength <= originalLength) {
      return originalValue.substring(0, returnLength);
    }

    int paddingLengthRequired = returnLength - originalLength;
    int patternLength = pattern.length();
    byte[] bytes = new byte[returnLength];
    for (int i = 0; i < originalLength; i++) {
      bytes[i] = originalValue.byteAt(i);
    }
    for (int i = returnLength - paddingLengthRequired; i < returnLength; i++) {
      byte curByte = pattern.byteAt(i % patternLength);
      bytes[i] = curByte;
    }
    return new ByteString(bytes);
  }

  /** SQL {@code RPAD(binary, integer)} function. */
  public static ByteString rpad(ByteString originalValue, int returnLength) {
    return rpad(originalValue, returnLength, SINGLE_SPACE_BYTE_STRING);
  }

  /** SQL {@code ENDS_WITH(string, string)} function. */
  public static boolean endsWith(String s0, String s1) {
    return s0.endsWith(s1);
  }

  /** SQL {@code ENDS_WITH(binary, binary)} function. */
  public static boolean endsWith(ByteString s0, ByteString s1) {
    return s0.endsWith(s1);
  }

  /** SQL {@code STARTS_WITH(string, string)} function. */
  public static boolean startsWith(String s0, String s1) {
    return s0.startsWith(s1);
  }

  /** SQL {@code STARTS_WITH(binary, binary)} function. */
  public static boolean startsWith(ByteString s0, ByteString s1) {
    return s0.startsWith(s1);
  }

  /** SQL {@code SPLIT(string, string)} function. */
  public static List<String> split(String s, String delimiter) {
    if (s.isEmpty()) {
      return ImmutableList.of();
    }
    if (delimiter.isEmpty()) {
      return ImmutableList.of(s); // prevent mischief
    }
    final ImmutableList.Builder<String> list = ImmutableList.builder();
    for (int i = 0;;) {
      int j = s.indexOf(delimiter, i);
      if (j < 0) {
        list.add(s.substring(i));
        return list.build();
      }
      list.add(s.substring(i, j));
      i = j + delimiter.length();
    }
  }

  /** SQL {@code SPLIT(string)} function. */
  public static List<String> split(String s) {
    return split(s, ",");
  }

  /** SQL {@code SPLIT(binary, binary)} function. */
  public static List<ByteString> split(ByteString s, ByteString delimiter) {
    if (s.length() == 0) {
      return ImmutableList.of();
    }
    if (delimiter.length() == 0) {
      return ImmutableList.of(s); // prevent mischief
    }
    final ImmutableList.Builder<ByteString> list = ImmutableList.builder();
    for (int i = 0;;) {
      int j = s.indexOf(delimiter, i);
      if (j < 0) {
        list.add(s.substring(i));
        return list.build();
      }
      list.add(s.substring(i, j));
      i = j + delimiter.length();
    }
  }

  /** SQL <code>CONTAINS_SUBSTR(rows, substr)</code> operator. */
  public static @Nullable Boolean containsSubstr(Object [] rows,
      String substr) {
    // If rows have null arguments, it should return TRUE if substr is found, otherwise NULL
    boolean nullFlag = false;
    for (Object row : rows) {
      if (row == null) {
        nullFlag = true;
      } else if (row instanceof Object[]) {
        return containsSubstr((Object[]) row, substr);
      } else if (row instanceof ArrayList) {
        return containsSubstr((List) row, substr);
      } else if (normalize(row.toString()).contains(normalize(substr))) {
        return true;
      }
    }
    return nullFlag ? null : false;
  }

  /** SQL <code>CONTAINS_SUBSTR(arr, substr)</code> operator. */
  public static @Nullable Boolean containsSubstr(List arr, String substr) {
    // If array has null arguments, it should return TRUE if substr is found, otherwise NULL
    boolean nullFlag = false;
    for (Object item : arr) {
      if (item == null) {
        nullFlag = true;
      }
      if (item != null && containsSubstr(item, substr)) {
        return true;
      }
    }
    return nullFlag ? null : false;
  }

  /** SQL <code>CONTAINS_SUBSTR(jsonString, substr, json_scope&#61;&#62;jsonScope)</code>
  * operator. */
  public static boolean containsSubstr(String jsonString, String substr,
      String jsonScope) {
    LinkedHashMap<String, String> map =
        (LinkedHashMap<String, String>) JsonFunctions.dejsonize(jsonString);
    assert map != null;
    Set<String> keys = map.keySet();
    Collection<String> values = map.values();
    switch (JsonScope.valueOf(jsonScope)) {
    case JSON_KEYS:
      return keys.contains(substr);
    case JSON_KEYS_AND_VALUES:
      return keys.contains(substr) || values.contains(substr);
    case JSON_VALUES:
      return values.contains(substr);
    default:
      throw new IllegalArgumentException("json_scope argument must be one of: \"JSON_KEYS\", "
          + "\"JSON_VALUES\", \"JSON_KEYS_AND_VALUES\".");
    }
  }

  /** SQL <code>CONTAINS_SUBSTR(expr, substr)</code> operator. */
  public static boolean containsSubstr(Object expr, String substr) {
    expr = normalize(expr.toString());
    substr = normalize(substr);
    if (JsonFunctions.isJsonObject(expr.toString())) {
      return containsSubstr(expr.toString(), substr, "JSON_VALUES");
    }
    return ((String) expr).contains(substr);
  }

  /** SQL <code>CONTAINS_SUBSTR(boolean, substr)</code> operator. */
  public static boolean containsSubstr(boolean s, String substr) {
    return containsSubstr(String.valueOf(s), substr);
  }

  /** SQL <code>CONTAINS_SUBSTR(int, substr)</code> operator. */
  public static boolean containsSubstr(int s, String substr) {
    return containsSubstr(String.valueOf(s), substr);
  }

  /** SQL <code>CONTAINS_SUBSTR(long, substr)</code> operator. */
  public static boolean containsSubstr(long s, String substr) {
    return containsSubstr(String.valueOf(s), substr);
  }

  /** Helper for CONTAINS_SUBSTR. */
  private static String normalize(String s) {
    // Before values are compared, should be case folded and normalized using NFKC normalization
    s = StringEscapeUtils.unescapeJava(s);
    s = Normalizer.normalize(s, Normalizer.Form.NFKC);
    s = lower(s);
    return s;
  }

  /** SQL SUBSTRING(string FROM ...) function. */
  public static String substring(String c, int s) {
    final int s0 = s - 1;
    if (s0 <= 0) {
      return c;
    }
    if (s > c.length()) {
      return "";
    }
    return c.substring(s0);
  }

  /** SQL SUBSTRING(string FROM ... FOR ...) function. */
  public static String substring(String c, int s, int l) {
    int lc = c.length();
    long e = (long) s + (long) l;
    if (l < 0) {
      throw RESOURCE.illegalNegativeSubstringLength().ex();
    }
    // Prevent overflow in addition
    if (s > lc || e < 1L) {
      return "";
    }
    final int s0 = Math.max(s - 1, 0);
    final long e0 = Math.min(e - 1, (long) lc);
    // We know that e0 cannot exceed Integer.MAX_VALUE, since it's smaller than lc
    return c.substring(s0, (int) e0);
  }

  /** SQL SUBSTRING(binary FROM ...) function for binary. */
  public static ByteString substring(ByteString c, int s) {
    final int s0 = s - 1;
    if (s0 <= 0) {
      return c;
    }
    if (s > c.length()) {
      return ByteString.EMPTY;
    }
    return c.substring(s0);
  }

  /** SQL SUBSTRING(binary FROM ... FOR ...) function for binary. */
  public static ByteString substring(ByteString c, int s, int l) {
    int lc = c.length();
    int e = s + l;
    if (l < 0) {
      throw RESOURCE.illegalNegativeSubstringLength().ex();
    }
    if (s > lc || e < 1) {
      return ByteString.EMPTY;
    }
    final int s0 = Math.max(s - 1, 0);
    final int e0 = Math.min(e - 1, lc);
    return c.substring(s0, e0);
  }

  /** SQL UPPER(string) function. */
  public static String upper(String s) {
    return s.toUpperCase(Locale.ROOT);
  }

  /** SQL LOWER(string) function. */
  public static String lower(String s) {
    return s.toLowerCase(Locale.ROOT);
  }

  /** SQL INITCAP(string) function. */
  public static String initcap(String s) {
    // Assumes Alpha as [A-Za-z0-9]
    // white space is treated as everything else.
    final int len = s.length();
    boolean start = true;
    final StringBuilder newS = new StringBuilder();

    for (int i = 0; i < len; i++) {
      char curCh = s.charAt(i);
      final int c = (int) curCh;
      if (start) {  // curCh is whitespace or first character of word.
        if (c > 47 && c < 58) { // 0-9
          start = false;
        } else if (c > 64 && c < 91) {  // A-Z
          start = false;
        } else if (c > 96 && c < 123) {  // a-z
          start = false;
          curCh = (char) (c - 32); // Uppercase this character
        }
        // else {} whitespace
      } else {  // Inside of a word or white space after end of word.
        if (c > 47 && c < 58) { // 0-9
          // noop
        } else if (c > 64 && c < 91) {  // A-Z
          curCh = (char) (c + 32); // Lowercase this character
        } else if (c > 96 && c < 123) {  // a-z
          // noop
        } else { // whitespace
          start = true;
        }
      }
      newS.append(curCh);
    } // for each character in s
    return newS.toString();
  }

  /** SQL REVERSE(string) function. */
  public static String reverse(String s) {
    final StringBuilder buf = new StringBuilder(s);
    return buf.reverse().toString();
  }

  /** SQL LEVENSHTEIN(string1, string2) function. */
  public static int levenshtein(String string1, String string2) {
    return LEVENSHTEIN_DISTANCE.apply(string1, string2);
  }

  /** SQL ASCII(string) function. */
  public static int ascii(String s) {
    return s.isEmpty()
        ? 0 : s.codePointAt(0);
  }

  /** SQL REPEAT(string, int) function. */
  public static String repeat(String s, int n) {
    if (n < 1) {
      return "";
    }
    return Strings.repeat(s, n);
  }

  /** SQL SPACE(int) function. */
  public static String space(int n) {
    return repeat(" ", n);
  }

  /** SQL STRCMP(String,String) function. */
  public static int strcmp(String s0, String s1) {
    return (int) Math.signum(s1.compareTo(s0));
  }

  /** SQL SOUNDEX(string) function. */
  public static String soundex(String s) {
    return SOUNDEX.soundex(s);
  }

  /** SQL SOUNDEX(string) function but return original s when not mapped. */
  public static String soundexSpark(String s) {
    try {
      return SOUNDEX.soundex(s);
    } catch (IllegalArgumentException ignore) {
      return s;
    }
  }

  /** SQL DIFFERENCE(string, string) function. */
  public static int difference(String s0, String s1) {
    String result0 = soundex(s0);
    String result1 = soundex(s1);
    for (int i = 0; i < SOUNDEX_LENGTH; i++) {
      if (result0.charAt(i) != result1.charAt(i)) {
        return i;
      }
    }
    return SOUNDEX_LENGTH;
  }

  /** SQL LEFT(string, integer) function. */
  public static String left(String s, int n) {
    if (n <= 0) {
      return "";
    }
    int len = s.length();
    if (n >= len) {
      return s;
    }
    return s.substring(0, n);
  }

  /** SQL LEFT(ByteString, integer) function. */
  public static ByteString left(ByteString s, int n) {
    if (n <= 0) {
      return ByteString.EMPTY;
    }
    int len = s.length();
    if (n >= len) {
      return s;
    }
    return s.substring(0, n);
  }

  /** SQL RIGHT(string, integer) function. */
  public static String right(String s, int n) {
    if (n <= 0) {
      return "";
    }
    int len = s.length();
    if (n >= len) {
      return s;
    }
    return s.substring(len - n);
  }

  /** SQL RIGHT(ByteString, integer) function. */
  public static ByteString right(ByteString s, int n) {
    if (n <= 0) {
      return ByteString.EMPTY;
    }
    final int len = s.length();
    if (n >= len) {
      return s;
    }
    return s.substring(len - n);
  }

  /** SQL CHAR(integer) function, as in MySQL and Spark.
   *
   * <p>Returns the ASCII character of {@code n} modulo 256,
   * or null if {@code n} &lt; 0. */
  public static @Nullable String charFromAscii(int n) {
    if (n < 0) {
      return null;
    }
    return String.valueOf(Character.toChars(n % 256));
  }

  /** SQL CHR(integer) function, as in Oracle and Postgres.
   *
   * <p>Returns the UTF-8 character whose code is {@code n}. */
  public static String charFromUtf8(int n) {
    return String.valueOf(Character.toChars(n));
  }

  /** SQL OCTET_LENGTH(binary) function. */
  public static int octetLength(ByteString s) {
    return s.length();
  }

  /** SQL CHARACTER_LENGTH(string) function. */
  public static int charLength(String s) {
    return s.length();
  }

  /** SQL BIT_LENGTH(string) function. */
  public static int bitLength(String s) {
    return s.getBytes(UTF_8).length * 8;
  }

  /** SQL BIT_LENGTH(binary) function. */
  public static int bitLength(ByteString s) {
    return s.length() * 8;
  }

  /** SQL BIT_GET(value, position) function. */
  public static byte bitGet(long value, int position) {
    checkPosition(position, java.lang.Long.SIZE - 1);
    return (byte) ((value >> position) & 1);
  }

  /** SQL BIT_GET(value, position) function. */
  public static byte bitGet(int value, int position) {
    checkPosition(position, java.lang.Integer.SIZE - 1);
    return (byte) ((value >> position) & 1);
  }

  /** SQL BIT_GET(value, position) function. */
  public static byte bitGet(short value, int position) {
    checkPosition(position, java.lang.Short.SIZE - 1);
    return (byte) ((value >> position) & 1);
  }

  /** SQL BIT_GET(value, position) function. */
  public static byte bitGet(byte value, int position) {
    checkPosition(position, java.lang.Byte.SIZE - 1);
    return (byte) ((value >> position) & 1);
  }

  private static void checkPosition(int position, int limit) {
    if (position < 0) {
      throw RESOURCE.illegalNegativeBitGetPosition(position).ex();
    }
    if (limit < position) {
      throw RESOURCE.illegalBitGetPositionExceedsLimit(position, limit).ex();
    }
  }

  /** SQL {@code string || string} operator. */
  public static String concat(String s0, String s1) {
    return s0 + s1;
  }

  /** Concatenates two strings.
   * Returns null only when both s0 and s1 are null,
   * otherwise null is treated as empty string. */
  public static @Nullable String concatWithNull(@Nullable String s0,
      @Nullable String s1) {
    if (s0 == null) {
      return s1;
    } else if (s1 == null) {
      return s0;
    } else {
      return s0 + s1;
    }
  }

  /** SQL {@code binary || binary} operator. */
  public static ByteString concat(ByteString s0, ByteString s1) {
    return s0.concat(s1);
  }

  /** SQL {@code CONCAT(arg0, arg1, arg2, ...)} function. */
  public static String concatMulti(String... args) {
    return String.join("", args);
  }

  /** SQL {@code CONCAT(arg0, ...)} function which can accept null
   * but never return null. Always treats null as empty string. */
  public static String concatMultiWithNull(String... args) {
    StringBuilder sb = new StringBuilder();
    for (String arg : args) {
      sb.append(arg == null ? "" : arg);
    }
    return sb.toString();
  }

  /** SQL {@code CONCAT_WS(sep, arg1, arg2, ...)} function;
   * treats null arguments as empty strings. */
  public static String concatMultiWithSeparator(String... args) {
    // the separator arg could be null
    final String sep = args[0] == null ? "" : args[0];
    StringBuilder sb = new StringBuilder();
    for (int i = 1; i < args.length; i++) {
      if (args[i] != null) {
        if (i < args.length - 1) {
          sb.append(args[i]).append(sep);
        } else {
          // no separator after the last arg
          sb.append(args[i]);
        }
      }
    }
    return sb.toString();
  }

  /** SQL {@code CONVERT(s, src_charset, dest_charset)} function. */
  public static String convertWithCharset(String s, String srcCharset,
      String destCharset) {
    final Charset src = SqlUtil.getCharset(srcCharset);
    final Charset dest = SqlUtil.getCharset(destCharset);
    byte[] bytes = s.getBytes(src);
    final CharsetDecoder decoder = dest.newDecoder();
    final ByteBuffer buffer = ByteBuffer.wrap(bytes);
    try {
      return decoder.decode(buffer).toString();
    } catch (CharacterCodingException ex) {
      throw RESOURCE.charsetEncoding(s, dest.name()).ex();
    }
  }

  /** SQL {@code TRANSLATE(s USING transcodingName)} function,
   * also known as {@code CONVERT(s USING transcodingName)}. */
  public static String translateWithCharset(String s, String transcodingName) {
    final Charset charset = SqlUtil.getCharset(transcodingName);
    byte[] bytes = s.getBytes(Charset.defaultCharset());
    final CharsetDecoder decoder = charset.newDecoder();
    final ByteBuffer buffer = ByteBuffer.wrap(bytes);
    try {
      return decoder.decode(buffer).toString();
    } catch (CharacterCodingException ex) {
      throw RESOURCE.charsetEncoding(s, charset.name()).ex();
    }
  }

  /** State for {@code PARSE_URL}. */
  @Deterministic
  public static class ParseUrlFunction {
    static Pattern keyToPattern(String keyToExtract) {
      return Pattern.compile("(&|^)" + keyToExtract + "=([^&]*)");
    }

    private final LoadingCache<String, Pattern> cache =
        CacheBuilder.newBuilder()
            .maximumSize(FUNCTION_LEVEL_CACHE_MAX_SIZE.value())
            .build(CacheLoader.from(ParseUrlFunction::keyToPattern));

    /** SQL {@code PARSE_URL(urlStr, partToExtract, keyToExtract)} function. */
    public @Nullable String parseUrl(String urlStr, String partToExtract,
        String keyToExtract) {
      if (!partToExtract.equals("QUERY")) {
        return null;
      }

      String query = parseUrl(urlStr, partToExtract);
      if (query == null) {
        return null;
      }

      Pattern p = cache.getUnchecked(keyToExtract);
      Matcher m = p.matcher(query);
      return m.find() ? m.group(2) : null;
    }

    /** SQL {@code PARSE_URL(urlStr, partToExtract)} function. */
    public @Nullable String parseUrl(String urlStr, String partToExtract) {
      URI uri;
      try {
        uri = new URI(urlStr);
      } catch (URISyntaxException e) {
        return null;
      }

      PartToExtract part;
      try {
        part = PartToExtract.valueOf(partToExtract);
      } catch (IllegalArgumentException e) {
        return null;
      }

      switch (part) {
      case HOST:
        return uri.getHost();
      case PATH:
        return uri.getRawPath();
      case QUERY:
        return uri.getRawQuery();
      case REF:
        return uri.getRawFragment();
      case PROTOCOL:
        return uri.getScheme();
      case FILE:
        if (uri.getRawQuery() != null) {
          return uri.getRawPath() + "?" + uri.getRawQuery();
        } else {
          return uri.getRawPath();
        }
      case AUTHORITY:
        return uri.getRawAuthority();
      case USERINFO:
        return uri.getRawUserInfo();
      default:
        return null;
      }
    }
  }

  /** SQL {@code RTRIM} function applied to string. */
  public static String rtrim(String s) {
    return trim(false, true, " ", s);
  }

  /** SQL {@code LTRIM} function. */
  public static String ltrim(String s) {
    return trim(true, false, " ", s);
  }

  /** SQL {@code TRIM(... seek FROM s)} function. */
  public static String trim(boolean left, boolean right, String seek,
      String s) {
    return trim(left, right, seek, s, true);
  }

  public static String trim(boolean left, boolean right, String seek,
      String s, boolean strict) {
    if (strict && seek.length() != 1) {
      throw RESOURCE.trimError().ex();
    }
    int j = s.length();
    if (right) {
      for (;;) {
        if (j == 0) {
          return "";
        }
        if (seek.indexOf(s.charAt(j - 1)) < 0) {
          break;
        }
        --j;
      }
    }
    int i = 0;
    if (left) {
      for (;;) {
        if (i == j) {
          return "";
        }
        if (seek.indexOf(s.charAt(i)) < 0) {
          break;
        }
        ++i;
      }
    }
    return s.substring(i, j);
  }

  /** SQL {@code TRIM} function applied to binary string. */
  public static ByteString trim(ByteString s) {
    return trim_(s, true, true);
  }

  /** Helper for CAST. */
  public static ByteString rtrim(ByteString s) {
    return trim_(s, false, true);
  }

  /** SQL {@code TRIM} function applied to binary string. */
  private static ByteString trim_(ByteString s, boolean left, boolean right) {
    int j = s.length();
    if (right) {
      for (;;) {
        if (j == 0) {
          return ByteString.EMPTY;
        }
        if (s.byteAt(j - 1) != 0) {
          break;
        }
        --j;
      }
    }
    int i = 0;
    if (left) {
      for (;;) {
        if (i == j) {
          return ByteString.EMPTY;
        }
        if (s.byteAt(i) != 0) {
          break;
        }
        ++i;
      }
    }
    return s.substring(i, j);
  }

  /** SQL {@code OVERLAY} function. */
  public static String overlay(String s, String r, int start) {
    return s.substring(0, start - 1)
        + r
        + s.substring(start - 1 + r.length());
  }

  /** SQL {@code OVERLAY} function. */
  public static String overlay(String s, String r, int start, int length) {
    return s.substring(0, start - 1)
        + r
        + s.substring(start - 1 + length);
  }

  /** SQL {@code OVERLAY} function applied to binary strings. */
  public static ByteString overlay(ByteString s, ByteString r, int start) {
    return s.substring(0, start - 1)
        .concat(r)
        .concat(s.substring(start - 1 + r.length()));
  }

  /** SQL {@code OVERLAY} function applied to binary strings. */
  public static ByteString overlay(ByteString s, ByteString r, int start,
      int length) {
    return s.substring(0, start - 1)
        .concat(r)
        .concat(s.substring(start - 1 + length));
  }

  /** State for {@code LIKE}, {@code ILIKE}. */
  @Deterministic
  public static class LikeFunction {
    /** Key for cache of compiled regular expressions. */
    private static final class Key {
      final String pattern;
      final @Nullable String escape;
      final int flags;

      Key(String pattern, @Nullable String escape, int flags) {
        this.pattern = pattern;
        this.escape = escape;
        this.flags = flags;
      }

      @Override public int hashCode() {
        return pattern.hashCode()
            ^ (escape == null ? 0 : escape.hashCode())
            ^ flags;
      }

      @Override public boolean equals(@Nullable Object obj) {
        return this == obj
            || obj instanceof Key
            && pattern.equals(((Key) obj).pattern)
            && Objects.equals(escape, ((Key) obj).escape)
            && flags == ((Key) obj).flags;
      }

      Pattern toPattern() {
        String regex = Like.sqlToRegexLike(pattern, escape);
        return Pattern.compile(regex, flags);
      }
    }

    private final LoadingCache<Key, Pattern> cache =
        CacheBuilder.newBuilder()
            .maximumSize(FUNCTION_LEVEL_CACHE_MAX_SIZE.value())
            .build(CacheLoader.from(Key::toPattern));

    /** SQL {@code LIKE} function. */
    public boolean like(String s, String pattern) {
      final Key key = new Key(pattern, null, 0);
      return cache.getUnchecked(key).matcher(s).matches();
    }

    /** SQL {@code LIKE} function with escape. */
    public boolean like(String s, String pattern, String escape) {
      final Key key = new Key(pattern, escape, 0);
      return cache.getUnchecked(key).matcher(s).matches();
    }

    /** SQL {@code ILIKE} function. */
    public boolean ilike(String s, String pattern) {
      final Key key = new Key(pattern, null, Pattern.CASE_INSENSITIVE);
      return cache.getUnchecked(key).matcher(s).matches();
    }

    /** SQL {@code ILIKE} function with escape. */
    public boolean ilike(String s, String pattern, String escape) {
      final Key key = new Key(pattern, escape, Pattern.CASE_INSENSITIVE);
      return cache.getUnchecked(key).matcher(s).matches();
    }
  }

  /** State for {@code SIMILAR} function. */
  @Deterministic
  public static class SimilarFunction {
    private final LoadingCache<String, Pattern> cache =
        CacheBuilder.newBuilder()
            .maximumSize(FUNCTION_LEVEL_CACHE_MAX_SIZE.value())
            .build(
                CacheLoader.from(pattern ->
                    Pattern.compile(Like.sqlToRegexSimilar(pattern, null))));

    /** SQL {@code SIMILAR} function. */
    public boolean similar(String s, String pattern) {
      return cache.getUnchecked(pattern).matcher(s).matches();
    }
  }

  /** State for {@code SIMILAR} function with escape. */
  public static class SimilarEscapeFunction {
    /** Cache key. */
    private static class Key extends MapEntry<String, String> {
      Key(String formatModel, String format) {
        super(formatModel, format);
      }

      Pattern toPattern() {
        return Pattern.compile(Like.sqlToRegexSimilar(t, u));
      }
    }

    private final LoadingCache<Key, Pattern> cache =
        CacheBuilder.newBuilder()
            .maximumSize(FUNCTION_LEVEL_CACHE_MAX_SIZE.value())
            .build(CacheLoader.from(Key::toPattern));

    /** SQL {@code SIMILAR} function with escape. */
    public boolean similar(String s, String pattern, String escape) {
      return cache.getUnchecked(new Key(pattern, escape))
          .matcher(s).matches();
    }
  }

  /** State for posix regex function. */
  @Deterministic
  public static class PosixRegexFunction {
    private final LoadingCache<Ord<String>, Pattern> cache =
        CacheBuilder.newBuilder()
            .maximumSize(FUNCTION_LEVEL_CACHE_MAX_SIZE.value())
            .build(
                CacheLoader.from(pattern ->
                    Like.posixRegexToPattern(pattern.e, pattern.i)));

    boolean posixRegex(String s, String regex, int flags) {
      final Ord<String> key = Ord.of(flags, regex);
      return cache.getUnchecked(key).matcher(s).find();
    }

    /** Posix regex, case-insensitive. */
    public boolean posixRegexInsensitive(String s, String regex) {
      return posixRegex(s, regex, Pattern.CASE_INSENSITIVE);
    }

    /** Posix regex, case-sensitive. */
    public boolean posixRegexSensitive(String s, String regex) {
      return posixRegex(s, regex, 0);
    }
  }

  // =

  /** SQL <code>=</code> operator applied to BigDecimal values (neither may be
   * null). */
  public static boolean eq(BigDecimal b0, BigDecimal b1) {
    return b0.stripTrailingZeros().equals(b1.stripTrailingZeros());
  }

  /** SQL <code>=</code> operator applied to Object[] values (neither may be
   * null). */
  public static boolean eq(@Nullable Object @Nullable [] b0, @Nullable Object @Nullable [] b1) {
    return Arrays.deepEquals(b0, b1);
  }

  /** SQL <code>=</code> operator applied to Object values (including String;
   * neither side may be null). */
  public static boolean eq(Object b0, Object b1) {
    return b0.equals(b1);
  }

  /** SQL <code>=</code> operator applied to String values with a certain Comparator. */
  public static boolean eq(String s0, String s1, Comparator<String> comparator) {
    return comparator.compare(s0, s1) == 0;
  }

  /** SQL <code>=</code> operator applied to Object values (at least one operand
   * has ANY type; neither may be null). */
  public static boolean eqAny(Object b0, Object b1) {
    if (b0.getClass().equals(b1.getClass())) {
      // The result of SqlFunctions.eq(BigDecimal, BigDecimal) makes more sense
      // than BigDecimal.equals(BigDecimal). So if both of types are BigDecimal,
      // we just use SqlFunctions.eq(BigDecimal, BigDecimal).
      if (BigDecimal.class.isInstance(b0)) {
        return eq((BigDecimal) b0, (BigDecimal) b1);
      } else {
        return b0.equals(b1);
      }
    } else if (allAssignable(Number.class, b0, b1)) {
      return eq(toBigDecimal((Number) b0), toBigDecimal((Number) b1));
    }
    // We shouldn't rely on implementation even though overridden equals can
    // handle other types which may create worse result: for example,
    // a.equals(b) != b.equals(a)
    return false;
  }

  /** Returns whether two objects can both be assigned to a given class. */
  private static boolean allAssignable(Class clazz, Object o0, Object o1) {
    return clazz.isInstance(o0) && clazz.isInstance(o1);
  }

  // <>

  /** SQL <code>&lt;gt;</code> operator applied to BigDecimal values. */
  public static boolean ne(BigDecimal b0, BigDecimal b1) {
    return b0.compareTo(b1) != 0;
  }

  /** SQL <code>&lt;gt;</code> operator applied to Object values (including
   * String; neither side may be null). */
  public static boolean ne(Object b0, Object b1) {
    return !eq(b0, b1);
  }

  /** SQL <code>&lt;gt;</code> operator applied to OString values with a certain Comparator. */
  public static boolean ne(String s0, String s1, Comparator<String> comparator) {
    return !eq(s0, s1, comparator);
  }

  /** SQL <code>&lt;gt;</code> operator applied to Object values (at least one
   * operand has ANY type, including String; neither may be null). */
  public static boolean neAny(Object b0, Object b1) {
    return !eqAny(b0, b1);
  }

  // <

  /** SQL <code>&lt;</code> operator applied to boolean values. */
  public static boolean lt(boolean b0, boolean b1) {
    return Boolean.compare(b0, b1) < 0;
  }

  /** SQL <code>&lt;</code> operator applied to String values. */
  public static boolean lt(String b0, String b1) {
    return b0.compareTo(b1) < 0;
  }

  /** SQL <code>&lt;</code> operator applied to String values. */
  public static boolean lt(String b0, String b1, Comparator<String> comparator) {
    return comparator.compare(b0, b1) < 0;
  }

  /** SQL <code>&lt;</code> operator applied to ByteString values. */
  public static boolean lt(ByteString b0, ByteString b1) {
    return b0.compareTo(b1) < 0;
  }

  /** SQL <code>&lt;</code> operator applied to BigDecimal values. */
  public static boolean lt(BigDecimal b0, BigDecimal b1) {
    return b0.compareTo(b1) < 0;
  }

  /** Returns whether {@code b0} is less than {@code b1}
   * (or {@code b1} is null). Helper for {@code ARG_MIN}. */
  public static <T extends Comparable<T>> boolean ltNullable(T b0, T b1) {
    return b1 == null || b0 != null && b0.compareTo(b1) < 0;
  }

  public static boolean lt(byte b0, byte b1) {
    return b0 < b1;
  }

  public static boolean lt(char b0, char b1) {
    return b0 < b1;
  }

  public static boolean lt(short b0, short b1) {
    return b0 < b1;
  }

  public static boolean lt(int b0, int b1) {
    return b0 < b1;
  }

  public static boolean lt(long b0, long b1) {
    return b0 < b1;
  }

  public static boolean lt(float b0, float b1) {
    return b0 < b1;
  }

  public static boolean lt(double b0, double b1) {
    return b0 < b1;
  }

  /** SQL <code>&lt;</code> operator applied to Object values. */
  public static boolean ltAny(Object b0, Object b1) {
    if (b0.getClass().equals(b1.getClass())
        && b0 instanceof Comparable) {
      //noinspection unchecked
      return ((Comparable) b0).compareTo(b1) < 0;
    } else if (allAssignable(Number.class, b0, b1)) {
      return lt(toBigDecimal((Number) b0), toBigDecimal((Number) b1));
    }

    throw notComparable("<", b0, b1);
  }

  // <=

  /** SQL <code>&le;</code> operator applied to boolean values. */
  public static boolean le(boolean b0, boolean b1) {
    return Boolean.compare(b0, b1) <= 0;
  }

  /** SQL <code>&le;</code> operator applied to String values. */
  public static boolean le(String b0, String b1) {
    return b0.compareTo(b1) <= 0;
  }

  /** SQL <code>&le;</code> operator applied to String values. */
  public static boolean le(String b0, String b1, Comparator<String> comparator) {
    return comparator.compare(b0, b1) <= 0;
  }

  /** SQL <code>&le;</code> operator applied to ByteString values. */
  public static boolean le(ByteString b0, ByteString b1) {
    return b0.compareTo(b1) <= 0;
  }

  /** SQL <code>&le;</code> operator applied to BigDecimal values. */
  public static boolean le(BigDecimal b0, BigDecimal b1) {
    return b0.compareTo(b1) <= 0;
  }

  /** SQL <code>&le;</code> operator applied to Object values (at least one
   * operand has ANY type; neither may be null). */
  public static boolean leAny(Object b0, Object b1) {
    if (b0.getClass().equals(b1.getClass())
        && b0 instanceof Comparable) {
      //noinspection unchecked
      return ((Comparable) b0).compareTo(b1) <= 0;
    } else if (allAssignable(Number.class, b0, b1)) {
      return le(toBigDecimal((Number) b0), toBigDecimal((Number) b1));
    }

    throw notComparable("<=", b0, b1);
  }

  // >

  /** SQL <code>&gt;</code> operator applied to boolean values. */
  public static boolean gt(boolean b0, boolean b1) {
    return Boolean.compare(b0, b1) > 0;
  }

  /** SQL <code>&gt;</code> operator applied to String values. */
  public static boolean gt(String b0, String b1) {
    return b0.compareTo(b1) > 0;
  }

  /** SQL <code>&gt;</code> operator applied to String values. */
  public static boolean gt(String b0, String b1, Comparator<String> comparator) {
    return comparator.compare(b0, b1) > 0;
  }

  /** SQL <code>&gt;</code> operator applied to ByteString values. */
  public static boolean gt(ByteString b0, ByteString b1) {
    return b0.compareTo(b1) > 0;
  }

  /** SQL <code>&gt;</code> operator applied to BigDecimal values. */
  public static boolean gt(BigDecimal b0, BigDecimal b1) {
    return b0.compareTo(b1) > 0;
  }

  /** Returns whether {@code b0} is greater than {@code b1}
   * (or {@code b1} is null). Helper for {@code ARG_MAX}. */
  public static <T extends Comparable<T>> boolean gtNullable(T b0, T b1) {
    return b1 == null || b0 != null && b0.compareTo(b1) > 0;
  }

  public static boolean gt(byte b0, byte b1) {
    return b0 > b1;
  }

  public static boolean gt(char b0, char b1) {
    return b0 > b1;
  }

  public static boolean gt(short b0, short b1) {
    return b0 > b1;
  }

  public static boolean gt(int b0, int b1) {
    return b0 > b1;
  }

  public static boolean gt(long b0, long b1) {
    return b0 > b1;
  }

  public static boolean gt(float b0, float b1) {
    return b0 > b1;
  }

  public static boolean gt(double b0, double b1) {
    return b0 > b1;
  }

  /** SQL <code>&gt;</code> operator applied to Object values (at least one
   * operand has ANY type; neither may be null). */
  public static boolean gtAny(Object b0, Object b1) {
    if (b0.getClass().equals(b1.getClass())
        && b0 instanceof Comparable) {
      //noinspection unchecked
      return ((Comparable) b0).compareTo(b1) > 0;
    } else if (allAssignable(Number.class, b0, b1)) {
      return gt(toBigDecimal((Number) b0), toBigDecimal((Number) b1));
    }

    throw notComparable(">", b0, b1);
  }

  // >=

  /** SQL <code>&ge;</code> operator applied to boolean values. */
  public static boolean ge(boolean b0, boolean b1) {
    return Boolean.compare(b0, b1) >= 0;
  }

  /** SQL <code>&ge;</code> operator applied to String values. */
  public static boolean ge(String b0, String b1) {
    return b0.compareTo(b1) >= 0;
  }

  /** SQL <code>&ge;</code> operator applied to String values. */
  public static boolean ge(String b0, String b1, Comparator<String> comparator) {
    return comparator.compare(b0, b1) >= 0;
  }

  /** SQL <code>&ge;</code> operator applied to ByteString values. */
  public static boolean ge(ByteString b0, ByteString b1) {
    return b0.compareTo(b1) >= 0;
  }

  /** SQL <code>&ge;</code> operator applied to BigDecimal values. */
  public static boolean ge(BigDecimal b0, BigDecimal b1) {
    return b0.compareTo(b1) >= 0;
  }

  /** SQL <code>&ge;</code> operator applied to Object values (at least one
   * operand has ANY type; neither may be null). */
  public static boolean geAny(Object b0, Object b1) {
    if (b0.getClass().equals(b1.getClass())
        && b0 instanceof Comparable) {
      //noinspection unchecked
      return ((Comparable) b0).compareTo(b1) >= 0;
    } else if (allAssignable(Number.class, b0, b1)) {
      return ge(toBigDecimal((Number) b0), toBigDecimal((Number) b1));
    }

    throw notComparable(">=", b0, b1);
  }

  // +

  /** SQL <code>+</code> operator applied to int values. */
  public static int plus(int b0, int b1) {
    return b0 + b1;
  }

  /** SQL <code>+</code> operator applied to int values; left side may be
   * null. */
  public static @PolyNull Integer plus(@PolyNull Integer b0, int b1) {
    return b0 == null ? castNonNull(null) : (b0 + b1);
  }

  /** SQL <code>+</code> operator applied to int values; right side may be
   * null. */
  public static @PolyNull Integer plus(int b0, @PolyNull Integer b1) {
    return b1 == null ? castNonNull(null) : (b0 + b1);
  }

  /** SQL <code>+</code> operator applied to nullable int values. */
  public static @PolyNull Integer plus(@PolyNull Integer b0, @PolyNull Integer b1) {
    return (b0 == null || b1 == null) ? castNonNull(null) : (b0 + b1);
  }

  /** SQL <code>+</code> operator applied to nullable long and int values. */
  public static @PolyNull Long plus(@PolyNull Long b0, @PolyNull Integer b1) {
    return (b0 == null || b1 == null)
        ? castNonNull(null)
        : (b0.longValue() + b1.longValue());
  }

  /** SQL <code>+</code> operator applied to nullable int and long values. */
  public static @PolyNull Long plus(@PolyNull Integer b0, @PolyNull Long b1) {
    return (b0 == null || b1 == null)
        ? castNonNull(null)
        : (b0.longValue() + b1.longValue());
  }

  /** SQL <code>+</code> operator applied to BigDecimal values. */
  public static @PolyNull BigDecimal plus(@PolyNull BigDecimal b0,
      @PolyNull BigDecimal b1) {
    return (b0 == null || b1 == null) ? castNonNull(null) : b0.add(b1);
  }

  /** SQL <code>+</code> operator applied to Object values (at least one operand
   * has ANY type; either may be null). */
  public static @PolyNull Object plusAny(@PolyNull Object b0,
      @PolyNull Object b1) {
    if (b0 == null || b1 == null) {
      return castNonNull(null);
    }

    if (allAssignable(Number.class, b0, b1)) {
      return plus(toBigDecimal((Number) b0), toBigDecimal((Number) b1));
    }

    throw notArithmetic("+", b0, b1);
  }

  // -

  /** SQL <code>-</code> operator applied to int values. */
  public static int minus(int b0, int b1) {
    return b0 - b1;
  }

  /** SQL <code>-</code> operator applied to int values; left side may be
   * null. */
  public static @PolyNull Integer minus(@PolyNull Integer b0, int b1) {
    return b0 == null ? castNonNull(null) : (b0 - b1);
  }

  /** SQL <code>-</code> operator applied to int values; right side may be
   * null. */
  public static @PolyNull Integer minus(int b0, @PolyNull Integer b1) {
    return b1 == null ? castNonNull(null) : (b0 - b1);
  }

  /** SQL <code>-</code> operator applied to nullable int values. */
  public static @PolyNull Integer minus(@PolyNull Integer b0, @PolyNull Integer b1) {
    return (b0 == null || b1 == null) ? castNonNull(null) : (b0 - b1);
  }

  /** SQL <code>-</code> operator applied to nullable long and int values. */
  public static @PolyNull Long minus(@PolyNull Long b0, @PolyNull Integer b1) {
    return (b0 == null || b1 == null)
        ? castNonNull(null)
        : (b0.longValue() - b1.longValue());
  }

  /** SQL <code>-</code> operator applied to nullable int and long values. */
  public static @PolyNull Long minus(@PolyNull Integer b0, @PolyNull Long b1) {
    return (b0 == null || b1 == null)
        ? castNonNull(null)
        : (b0.longValue() - b1.longValue());
  }

  /** SQL <code>-</code> operator applied to nullable BigDecimal values. */
  public static @PolyNull BigDecimal minus(@PolyNull BigDecimal b0,
      @PolyNull BigDecimal b1) {
    return (b0 == null || b1 == null) ? castNonNull(null) : b0.subtract(b1);
  }

  /** SQL <code>-</code> operator applied to Object values (at least one operand
   * has ANY type; either may be null). */
  public static @PolyNull Object minusAny(@PolyNull Object b0, @PolyNull Object b1) {
    if (b0 == null || b1 == null) {
      return castNonNull(null);
    }

    if (allAssignable(Number.class, b0, b1)) {
      return minus(toBigDecimal((Number) b0), toBigDecimal((Number) b1));
    }

    throw notArithmetic("-", b0, b1);
  }

  // /

  /** SQL <code>/</code> operator applied to int values. */
  public static int divide(int b0, int b1) {
    return b0 / b1;
  }

  /** SQL <code>/</code> operator applied to int values; left side may be
   * null. */
  public static @PolyNull Integer divide(@PolyNull Integer b0, int b1) {
    return b0 == null ? castNonNull(null) : (b0 / b1);
  }

  /** SQL <code>/</code> operator applied to int values; right side may be
   * null. */
  public static @PolyNull Integer divide(int b0, @PolyNull Integer b1) {
    return b1 == null ? castNonNull(null) : (b0 / b1);
  }

  /** SQL <code>/</code> operator applied to nullable int values. */
  public static @PolyNull Integer divide(@PolyNull Integer b0,
      @PolyNull Integer b1) {
    return (b0 == null || b1 == null) ? castNonNull(null) : (b0 / b1);
  }

  /** SQL <code>/</code> operator applied to nullable long and int values. */
  public static @PolyNull Long divide(Long b0, @PolyNull Integer b1) {
    return (b0 == null || b1 == null)
        ? castNonNull(null)
        : (b0.longValue() / b1.longValue());
  }

  /** SQL <code>/</code> operator applied to nullable int and long values. */
  public static @PolyNull Long divide(@PolyNull Integer b0, @PolyNull Long b1) {
    return (b0 == null || b1 == null)
        ? castNonNull(null)
        : (b0.longValue() / b1.longValue());
  }

  /** SQL <code>/</code> operator applied to BigDecimal values. */
  public static @PolyNull BigDecimal divide(@PolyNull BigDecimal b0,
      @PolyNull BigDecimal b1) {
    return (b0 == null || b1 == null)
        ? castNonNull(null)
        : b0.divide(b1, MathContext.DECIMAL64);
  }

  /** SQL <code>/</code> operator applied to Object values (at least one operand
   * has ANY type; either may be null). */
  public static @PolyNull Object divideAny(@PolyNull Object b0,
      @PolyNull Object b1) {
    if (b0 == null || b1 == null) {
      return castNonNull(null);
    }

    if (allAssignable(Number.class, b0, b1)) {
      return divide(toBigDecimal((Number) b0), toBigDecimal((Number) b1));
    }

    throw notArithmetic("/", b0, b1);
  }

  public static int divide(int b0, BigDecimal b1) {
    return BigDecimal.valueOf(b0)
        .divide(b1, RoundingMode.HALF_DOWN).intValue();
  }

  public static long divide(long b0, BigDecimal b1) {
    return BigDecimal.valueOf(b0)
        .divide(b1, RoundingMode.HALF_DOWN).longValue();
  }

  // *

  /** SQL <code>*</code> operator applied to int values. */
  public static int multiply(int b0, int b1) {
    return b0 * b1;
  }

  /** SQL <code>*</code> operator applied to int values; left side may be
   * null. */
  public static @PolyNull Integer multiply(@PolyNull Integer b0, int b1) {
    return b0 == null ? castNonNull(null) : (b0 * b1);
  }

  /** SQL <code>*</code> operator applied to int values; right side may be
   * null. */
  public static @PolyNull Integer multiply(int b0, @PolyNull Integer b1) {
    return b1 == null ? castNonNull(null) : (b0 * b1);
  }

  /** SQL <code>*</code> operator applied to nullable int values. */
  public static @PolyNull Integer multiply(@PolyNull Integer b0,
      @PolyNull Integer b1) {
    return (b0 == null || b1 == null) ? castNonNull(null) : (b0 * b1);
  }

  /** SQL <code>*</code> operator applied to nullable long and int values. */
  public static @PolyNull Long multiply(@PolyNull Long b0, @PolyNull Integer b1) {
    return (b0 == null || b1 == null)
        ? castNonNull(null)
        : (b0.longValue() * b1.longValue());
  }

  /** SQL <code>*</code> operator applied to nullable int and long values. */
  public static @PolyNull Long multiply(@PolyNull Integer b0, @PolyNull Long b1) {
    return (b0 == null || b1 == null)
        ? castNonNull(null)
        : (b0.longValue() * b1.longValue());
  }

  /** SQL <code>*</code> operator applied to nullable BigDecimal values. */
  public static @PolyNull BigDecimal multiply(@PolyNull BigDecimal b0,
      @PolyNull BigDecimal b1) {
    return (b0 == null || b1 == null) ? castNonNull(null) : b0.multiply(b1);
  }

  /** SQL <code>*</code> operator applied to Object values (at least one operand
   * has ANY type; either may be null). */
  public static @PolyNull Object multiplyAny(@PolyNull Object b0,
      @PolyNull Object b1) {
    if (b0 == null || b1 == null) {
      return castNonNull(null);
    }

    if (allAssignable(Number.class, b0, b1)) {
      return multiply(toBigDecimal((Number) b0), toBigDecimal((Number) b1));
    }

    throw notArithmetic("*", b0, b1);
  }

  /** SQL <code>SAFE_ADD</code> function applied to long values. */
  public static @Nullable Long safeAdd(long b0, long b1) {
    try {
      return Math.addExact(b0, b1);
    } catch (ArithmeticException e) {
      return null;
    }
  }

  /** SQL <code>SAFE_ADD</code> function applied to long and BigDecimal values. */
  public static @Nullable BigDecimal safeAdd(long b0, BigDecimal b1) {
    BigDecimal ans = BigDecimal.valueOf(b0).add(b1);
    return safeDecimal(ans) ? ans : null;
  }

  /** SQL <code>SAFE_ADD</code> function applied to BigDecimal and long values. */
  public static @Nullable BigDecimal safeAdd(BigDecimal b0, long b1) {
    return safeAdd(b1, b0);
  }

  /** SQL <code>SAFE_ADD</code> function applied to BigDecimal values. */
  public static @Nullable BigDecimal safeAdd(BigDecimal b0, BigDecimal b1) {
    BigDecimal ans = b0.add(b1);
    return safeDecimal(ans) ? ans : null;
  }

  /** SQL <code>SAFE_ADD</code> function applied to double and long values. */
  public static @Nullable Double safeAdd(double b0, long b1) {
    double ans = b0 + b1;
    return safeDouble(ans) || !Double.isFinite(b0) ? ans : null;
  }

  /** SQL <code>SAFE_ADD</code> function applied to long and double values. */
  public static @Nullable Double safeAdd(long b0, double b1) {
    return safeAdd(b1, b0);
  }

  /** SQL <code>SAFE_ADD</code> function applied to double and BigDecimal values. */
  public static @Nullable Double safeAdd(double b0, BigDecimal b1) {
    double ans = b0 + b1.doubleValue();
    return safeDouble(ans) || !Double.isFinite(b0) ? ans : null;
  }

  /** SQL <code>SAFE_ADD</code> function applied to BigDecimal and double values. */
  public static @Nullable Double safeAdd(BigDecimal b0, double b1) {
    return safeAdd(b1, b0);
  }

  /** SQL <code>SAFE_ADD</code> function applied to double values. */
  public static @Nullable Double safeAdd(double b0, double b1) {
    double ans = b0 + b1;
    boolean isFinite = Double.isFinite(b0) && Double.isFinite(b1);
    return safeDouble(ans) || !isFinite ? ans : null;
  }

  /** SQL <code>SAFE_MULTIPLY</code> function applied to long values. */
  public static @Nullable Long safeMultiply(long b0, long b1) {
    try {
      return Math.multiplyExact(b0, b1);
    } catch (ArithmeticException e) {
      return null;
    }
  }

  /** SQL <code>SAFE_MULTIPLY</code> function applied to long and BigDecimal values. */
  public static @Nullable BigDecimal safeMultiply(long b0, BigDecimal b1) {
    BigDecimal ans = BigDecimal.valueOf(b0).multiply(b1);
    return safeDecimal(ans) ? ans : null;
  }

  /** SQL <code>SAFE_MULTIPLY</code> function applied to BigDecimal and long values. */
  public static @Nullable BigDecimal safeMultiply(BigDecimal b0, long b1) {
    return safeMultiply(b1, b0);
  }

  /** SQL <code>SAFE_MULTIPLY</code> function applied to BigDecimal values. */
  public static @Nullable BigDecimal safeMultiply(BigDecimal b0, BigDecimal b1) {
    BigDecimal ans = b0.multiply(b1);
    return safeDecimal(ans) ? ans : null;
  }

  /** SQL <code>SAFE_MULTIPLY</code> function applied to double and long values. */
  public static @Nullable Double safeMultiply(double b0, long b1) {
    double ans = b0 * b1;
    return safeDouble(ans) || !Double.isFinite(b0) ? ans : null;
  }

  /** SQL <code>SAFE_MULTIPLY</code> function applied to long and double values. */
  public static @Nullable Double safeMultiply(long b0, double b1) {
    return safeMultiply(b1, b0);
  }

  /** SQL <code>SAFE_MULTIPLY</code> function applied to double and BigDecimal values. */
  public static @Nullable Double safeMultiply(double b0, BigDecimal b1) {
    double ans = b0 * b1.doubleValue();
    return safeDouble(ans) || !Double.isFinite(b0) ? ans : null;
  }

  /** SQL <code>SAFE_MULTIPLY</code> function applied to BigDecimal and double values. */
  public static @Nullable Double safeMultiply(BigDecimal b0, double b1) {
    return safeMultiply(b1, b0);
  }

  /** SQL <code>SAFE_MULTIPLY</code> function applied to double values. */
  public static @Nullable Double safeMultiply(double b0, double b1) {
    double ans = b0 * b1;
    boolean isFinite = Double.isFinite(b0) && Double.isFinite(b1);
    return safeDouble(ans) || !isFinite ? ans : null;
  }

  /** SQL <code>SAFE_SUBTRACT</code> function applied to long values. */
  public static @Nullable Long safeSubtract(long b0, long b1) {
    try {
      return Math.subtractExact(b0, b1);
    } catch (ArithmeticException e) {
      return null;
    }
  }

  /** SQL <code>SAFE_SUBTRACT</code> function applied to long and BigDecimal values. */
  public static @Nullable BigDecimal safeSubtract(long b0, BigDecimal b1) {
    BigDecimal ans = BigDecimal.valueOf(b0).subtract(b1);
    return safeDecimal(ans) ? ans : null;
  }

  /** SQL <code>SAFE_SUBTRACT</code> function applied to BigDecimal and long values. */
  public static @Nullable BigDecimal safeSubtract(BigDecimal b0, long b1) {
    BigDecimal ans = b0.subtract(BigDecimal.valueOf(b1));
    return safeDecimal(ans) ? ans : null;
  }

  /** SQL <code>SAFE_SUBTRACT</code> function applied to BigDecimal values. */
  public static @Nullable BigDecimal safeSubtract(BigDecimal b0, BigDecimal b1) {
    BigDecimal ans = b0.subtract(b1);
    return safeDecimal(ans) ? ans : null;
  }

  /** SQL <code>SAFE_SUBTRACT</code> function applied to double and long values. */
  public static @Nullable Double safeSubtract(double b0, long b1) {
    double ans = b0 - b1;
    return safeDouble(ans) || !Double.isFinite(b0) ? ans : null;
  }

  /** SQL <code>SAFE_SUBTRACT</code> function applied to long and double values. */
  public static @Nullable Double safeSubtract(long b0, double b1) {
    double ans = b0 - b1;
    return safeDouble(ans) || !Double.isFinite(b1) ? ans : null;
  }

  /** SQL <code>SAFE_SUBTRACT</code> function applied to double and BigDecimal values. */
  public static @Nullable Double safeSubtract(double b0, BigDecimal b1) {
    double ans = b0 - b1.doubleValue();
    return safeDouble(ans) || !Double.isFinite(b0) ? ans : null;
  }

  /** SQL <code>SAFE_SUBTRACT</code> function applied to BigDecimal and double values. */
  public static @Nullable Double safeSubtract(BigDecimal b0, double b1) {
    double ans = b0.doubleValue() - b1;
    return safeDouble(ans) || !Double.isFinite(b1) ? ans : null;
  }

  /** SQL <code>SAFE_SUBTRACT</code> function applied to double values. */
  public static @Nullable Double safeSubtract(double b0, double b1) {
    double ans = b0 - b1;
    boolean isFinite = Double.isFinite(b0) && Double.isFinite(b1);
    return safeDouble(ans) || !isFinite ? ans : null;
  }

  /** Returns whether a BigDecimal value is safe (that is, has not overflowed).
   * According to BigQuery, BigDecimal overflow occurs if the precision is greater
   * than 76 or the scale is greater than 38. */
  private static boolean safeDecimal(BigDecimal b) {
    return b.scale() <= 38 && b.precision() <= 76;
  }

  /** Returns whether a double value is safe (that is, has not overflowed). */
  private static boolean safeDouble(double d) {
    // If the double is positive and falls between the MIN and MAX double values,
    // overflow has not occurred. If the double is negative and falls between the
    // negated MIN and MAX double values, overflow has not occurred. Otherwise,
    // overflow has occurred. Important to note that 'Double.MIN_VALUE' refers to
    // minimum positive value.
    return Math.abs(d) > Double.MIN_VALUE && Math.abs(d) < Double.MAX_VALUE || d == 0;
  }

  private static RuntimeException notArithmetic(String op, Object b0,
      Object b1) {
    return RESOURCE.invalidTypesForArithmetic(b0.getClass().toString(),
        op, b1.getClass().toString()).ex();
  }

  private static RuntimeException notComparable(String op, Object b0,
      Object b1) {
    return RESOURCE.invalidTypesForComparison(b0.getClass().toString(),
        op, b1.getClass().toString()).ex();
  }

  /** Bitwise function <code>BIT_AND</code> applied to integer values. */
  public static long bitAnd(long b0, long b1) {
    return b0 & b1;
  }

  /** Bitwise function <code>BIT_AND</code> applied to binary values. */
  public static ByteString bitAnd(ByteString b0, ByteString b1) {
    return binaryOperator(b0, b1, (x, y) -> (byte) (x & y));
  }

  /** Bitwise function <code>BIT_OR</code> applied to integer values. */
  public static long bitOr(long b0, long b1) {
    return b0 | b1;
  }

  /** Bitwise function <code>BIT_OR</code> applied to binary values. */
  public static ByteString bitOr(ByteString b0, ByteString b1) {
    return binaryOperator(b0, b1, (x, y) -> (byte) (x | y));
  }

  /** Bitwise function <code>BIT_XOR</code> applied to integer values. */
  public static long bitXor(long b0, long b1) {
    return b0 ^ b1;
  }

  /** Bitwise function <code>BIT_XOR</code> applied to binary values. */
  public static ByteString bitXor(ByteString b0, ByteString b1) {
    return binaryOperator(b0, b1, (x, y) -> (byte) (x ^ y));
  }

  /**
   * Utility for bitwise function applied to two byteString values.
   *
   * @param b0 The first byteString value operand of bitwise function.
   * @param b1 The second byteString value operand of bitwise function.
   * @param bitOp BitWise binary operator.
   * @return ByteString after bitwise operation.
   */
  private static ByteString binaryOperator(
      ByteString b0, ByteString b1, BinaryOperator<Byte> bitOp) {
    if (b0.length() == 0) {
      return b1;
    }
    if (b1.length() == 0) {
      return b0;
    }

    if (b0.length() != b1.length()) {
      throw RESOURCE.differentLengthForBitwiseOperands(
          b0.length(), b1.length()).ex();
    }

    final byte[] result = new byte[b0.length()];
    for (int i = 0; i < b0.length(); i++) {
      result[i] = bitOp.apply(b0.byteAt(i), b1.byteAt(i));
    }

    return new ByteString(result);
  }

  // EXP

  /** SQL <code>EXP</code> operator applied to double values. */
  public static double exp(double b0) {
    return Math.exp(b0);
  }

  public static double exp(BigDecimal b0) {
    return Math.exp(b0.doubleValue());
  }

  // POWER

  /** SQL <code>POWER</code> operator applied to double values. */
  public static double power(double b0, double b1) {
    return Math.pow(b0, b1);
  }

  public static double power(double b0, BigDecimal b1) {
    return Math.pow(b0, b1.doubleValue());
  }

  public static double power(BigDecimal b0, double b1) {
    return Math.pow(b0.doubleValue(), b1);
  }

  public static double power(BigDecimal b0, BigDecimal b1) {
    return Math.pow(b0.doubleValue(), b1.doubleValue());
  }


  // LN, LOG, LOG10

  /** SQL {@code LOG(number, number2)} function applied to double values. */
  public static double log(double d0, double d1) {
    return Math.log(d0) / Math.log(d1);
  }

  /** SQL {@code LOG(number, number2)} function applied to
   * double and BigDecimal values. */
  public static double log(double d0, BigDecimal d1) {
    return Math.log(d0) / Math.log(d1.doubleValue());
  }

  /** SQL {@code LOG(number, number2)} function applied to
   * BigDecimal and double values. */
  public static double log(BigDecimal d0, double d1) {
    return Math.log(d0.doubleValue()) / Math.log(d1);
  }

  /** SQL {@code LOG(number, number2)} function applied to double values. */
  public static double log(BigDecimal d0, BigDecimal d1) {
    return Math.log(d0.doubleValue()) / Math.log(d1.doubleValue());
  }

  // MOD

  /** SQL <code>MOD</code> operator applied to byte values. */
  public static byte mod(byte b0, byte b1) {
    return (byte) (b0 % b1);
  }

  /** SQL <code>MOD</code> operator applied to short values. */
  public static short mod(short b0, short b1) {
    return (short) (b0 % b1);
  }

  /** SQL <code>MOD</code> operator applied to int values. */
  public static int mod(int b0, int b1) {
    return b0 % b1;
  }

  /** SQL <code>MOD</code> operator applied to long values. */
  public static long mod(long b0, long b1) {
    return b0 % b1;
  }

  // temporary
  public static BigDecimal mod(BigDecimal b0, int b1) {
    return mod(b0, BigDecimal.valueOf(b1));
  }

  // temporary
  public static BigDecimal mod(int b0, BigDecimal b1) {
    return mod(BigDecimal.valueOf(b0), b1);
  }

  public static BigDecimal mod(BigDecimal b0, BigDecimal b1) {
    final BigDecimal[] bigDecimals = b0.divideAndRemainder(b1);
    return bigDecimals[1];
  }

  // FLOOR

  public static double floor(double b0) {
    return Math.floor(b0);
  }

  public static float floor(float b0) {
    return (float) Math.floor(b0);
  }

  public static BigDecimal floor(BigDecimal b0) {
    return b0.setScale(0, RoundingMode.FLOOR);
  }

  /** SQL <code>FLOOR</code> operator applied to byte values. */
  public static byte floor(byte b0, byte b1) {
    return (byte) floor((int) b0, (int) b1);
  }

  /** SQL <code>FLOOR</code> operator applied to short values. */
  public static short floor(short b0, short b1) {
    return (short) floor((int) b0, (int) b1);
  }

  /** SQL <code>FLOOR</code> operator applied to int values. */
  public static int floor(int b0, int b1) {
    int r = b0 % b1;
    if (r < 0) {
      r += b1;
    }
    return b0 - r;
  }

  /** SQL <code>FLOOR</code> operator applied to long values. */
  public static long floor(long b0, long b1) {
    long r = b0 % b1;
    if (r < 0) {
      r += b1;
    }
    return b0 - r;
  }

  // temporary
  public static BigDecimal floor(BigDecimal b0, int b1) {
    return floor(b0, BigDecimal.valueOf(b1));
  }

  // temporary
  public static int floor(int b0, BigDecimal b1) {
    return floor(b0, b1.intValue());
  }

  public static BigDecimal floor(BigDecimal b0, BigDecimal b1) {
    final BigDecimal[] bigDecimals = b0.divideAndRemainder(b1);
    BigDecimal r = bigDecimals[1];
    if (r.signum() < 0) {
      r = r.add(b1);
    }
    return b0.subtract(r);
  }

  // CEIL

  public static double ceil(double b0) {
    return Math.ceil(b0);
  }

  public static float ceil(float b0) {
    return (float) Math.ceil(b0);
  }

  public static BigDecimal ceil(BigDecimal b0) {
    return b0.setScale(0, RoundingMode.CEILING);
  }

  /** SQL <code>CEIL</code> operator applied to byte values. */
  public static byte ceil(byte b0, byte b1) {
    return floor((byte) (b0 + b1 - 1), b1);
  }

  /** SQL <code>CEIL</code> operator applied to short values. */
  public static short ceil(short b0, short b1) {
    return floor((short) (b0 + b1 - 1), b1);
  }

  /** SQL <code>CEIL</code> operator applied to int values. */
  public static int ceil(int b0, int b1) {
    int r = b0 % b1;
    if (r > 0) {
      r -= b1;
    }
    return b0 - r;
  }

  /** SQL <code>CEIL</code> operator applied to long values. */
  public static long ceil(long b0, long b1) {
    return floor(b0 + b1 - 1, b1);
  }

  // temporary
  public static BigDecimal ceil(BigDecimal b0, int b1) {
    return ceil(b0, BigDecimal.valueOf(b1));
  }

  // temporary
  public static int ceil(int b0, BigDecimal b1) {
    return ceil(b0, b1.intValue());
  }

  public static BigDecimal ceil(BigDecimal b0, BigDecimal b1) {
    final BigDecimal[] bigDecimals = b0.divideAndRemainder(b1);
    BigDecimal r = bigDecimals[1];
    if (r.signum() > 0) {
      r = r.subtract(b1);
    }
    return b0.subtract(r);
  }

  // ABS

  /** SQL <code>ABS</code> operator applied to byte values. */
  public static byte abs(byte b0) {
    return (byte) Math.abs(b0);
  }

  /** SQL <code>ABS</code> operator applied to short values. */
  public static short abs(short b0) {
    return (short) Math.abs(b0);
  }

  /** SQL <code>ABS</code> operator applied to int values. */
  public static int abs(int b0) {
    return Math.abs(b0);
  }

  /** SQL <code>ABS</code> operator applied to long values. */
  public static long abs(long b0) {
    return Math.abs(b0);
  }

  /** SQL <code>ABS</code> operator applied to float values. */
  public static float abs(float b0) {
    return Math.abs(b0);
  }

  /** SQL <code>ABS</code> operator applied to double values. */
  public static double abs(double b0) {
    return Math.abs(b0);
  }

  /** SQL <code>ABS</code> operator applied to BigDecimal values. */
  public static BigDecimal abs(BigDecimal b0) {
    return b0.abs();
  }

  // ACOS
  /** SQL <code>ACOS</code> operator applied to BigDecimal values. */
  public static double acos(BigDecimal b0) {
    return Math.acos(b0.doubleValue());
  }

  /** SQL <code>ACOS</code> operator applied to double values. */
  public static double acos(double b0) {
    return Math.acos(b0);
  }

  // ACOSH
  /** SQL <code>ACOSH</code> operator applied to BigDecimal values. */
  public static double acosh(BigDecimal b0) {
    return acosh(b0.doubleValue());
  }

  /** SQL <code>ACOSH</code> operator applied to double values. */
  public static double acosh(double b0) {
    if (b0 < 1) {
      throw new IllegalArgumentException("Input parameter of acosh cannot be less than 1!");
    }
    return Math.log(Math.sqrt(b0 * b0 - 1.0d) + b0);
  }

  // ASIN
  /** SQL <code>ASIN</code> operator applied to BigDecimal values. */
  public static double asin(BigDecimal b0) {
    return Math.asin(b0.doubleValue());
  }

  /** SQL <code>ASIN</code> operator applied to double values. */
  public static double asin(double b0) {
    return Math.asin(b0);
  }

  // ASINH
  /** SQL <code>ASINH</code> operator applied to BigDecimal values. */
  public static double asinh(BigDecimal b0) {
    return asinh(b0.doubleValue());
  }

  /** SQL <code>ASINH</code> operator applied to double values. */
  public static double asinh(double b0) {
    final double sign;
    // check the sign bit of the raw representation to handle -0.
    if (Double.doubleToRawLongBits(b0) < 0) {
      b0 = Math.abs(b0);
      sign = -1.0d;
    } else {
      sign = 1.0d;
    }
    return sign * Math.log(Math.sqrt(b0 * b0 + 1.0d) + b0);
  }

  // ATAN
  /** SQL <code>ATAN</code> operator applied to BigDecimal values. */
  public static double atan(BigDecimal b0) {
    return Math.atan(b0.doubleValue());
  }

  /** SQL <code>ATAN</code> operator applied to double values. */
  public static double atan(double b0) {
    return Math.atan(b0);
  }

  // ATAN2
  /** SQL <code>ATAN2</code> operator applied to double/BigDecimal values. */
  public static double atan2(double b0, BigDecimal b1) {
    return Math.atan2(b0, b1.doubleValue());
  }

  /** SQL <code>ATAN2</code> operator applied to BigDecimal/double values. */
  public static double atan2(BigDecimal b0, double b1) {
    return Math.atan2(b0.doubleValue(), b1);
  }

  /** SQL <code>ATAN2</code> operator applied to BigDecimal values. */
  public static double atan2(BigDecimal b0, BigDecimal b1) {
    return Math.atan2(b0.doubleValue(), b1.doubleValue());
  }

  /** SQL <code>ATAN2</code> operator applied to double values. */
  public static double atan2(double b0, double b1) {
    return Math.atan2(b0, b1);
  }

  // ATANH
  /** SQL <code>ATANH</code> operator applied to BigDecimal values. */
  public static double atanh(BigDecimal b) {
    return atanh(b.doubleValue());
  }

  /** SQL <code>ATANH</code> operator applied to double values. */
  public static double atanh(double b) {
    if (Math.abs(b) >= 1) {
      throw new IllegalArgumentException("Input parameter of atanh cannot be out of the "
          + "range (-1, 1)!");
    }
    final double mult;
    // check the sign bit of the raw representation to handle -0.
    if (Double.doubleToRawLongBits(b) < 0) {
      b = Math.abs(b);
      mult = -0.5d;
    } else {
      mult = 0.5d;
    }
    return mult * Math.log((1.0d + b) / (1.0d - b));
  }

  // CBRT
  /** SQL <code>CBRT</code> operator applied to BigDecimal values. */
  public static double cbrt(BigDecimal b) {
    return cbrt(b.doubleValue());
  }

  /** SQL <code>CBRT</code> operator applied to double values. */
  public static double cbrt(double b) {
    return Math.cbrt(b);
  }

  // COS
  /** SQL <code>COS</code> operator applied to BigDecimal values. */
  public static double cos(BigDecimal b0) {
    return Math.cos(b0.doubleValue());
  }

  /** SQL <code>COS</code> operator applied to double values. */
  public static double cos(double b0) {
    return Math.cos(b0);
  }

  // COSH
  /** SQL <code>COSH</code> operator applied to BigDecimal values. */
  public static double cosh(BigDecimal b) {
    return cosh(b.doubleValue());
  }

  /** SQL <code>COSH</code> operator applied to double values. */
  public static double cosh(double b) {
    return Math.cosh(b);
  }

  // COT
  /** SQL <code>COT</code> operator applied to BigDecimal values. */
  public static double cot(BigDecimal b0) {
    return 1.0d / Math.tan(b0.doubleValue());
  }

  /** SQL <code>COT</code> operator applied to double values. */
  public static double cot(double b0) {
    return 1.0d / Math.tan(b0);
  }

  /** SQL <code>COTH</code> operator applied to BigDecimal values. */
  public static double coth(BigDecimal b0) {
    return 1.0d / Math.tanh(b0.doubleValue());
  }

  /** SQL <code>COTH</code> operator applied to double values. */
  public static double coth(double b0) {
    return 1.0d / Math.tanh(b0);
  }

  /** SQL <code>CSCH</code> operator applied to BigDecimal values. */
  public static double csch(BigDecimal b0) {
    return 1.0d / Math.sinh(b0.doubleValue());
  }

  /** SQL <code>CSCH</code> operator applied to double values. */
  public static double csch(double b0) {
    return 1.0d / Math.sinh(b0);
  }

  // DEGREES
  /** SQL <code>DEGREES</code> operator applied to BigDecimal values. */
  public static double degrees(BigDecimal b0) {
    return Math.toDegrees(b0.doubleValue());
  }

  /** SQL <code>DEGREES</code> operator applied to double values. */
  public static double degrees(double b0) {
    return Math.toDegrees(b0);
  }

  /** SQL <code>IS_INF</code> operator applied to BigDecimal values. */
  public static boolean isInf(BigDecimal b0) {
    return Double.isInfinite(b0.doubleValue());
  }

  /** SQL <code>IS_INF</code> operator applied to double values. */
  public static boolean isInf(double b0) {
    return Double.isInfinite(b0);
  }

  /** SQL <code>IS_INF</code> operator applied to float values. */
  public static boolean isInf(float b0) {
    return Float.isInfinite(b0);
  }

  /** SQL <code>IS_NAN</code> operator applied to BigDecimal values. */
  public static boolean isNaN(BigDecimal b0) {
    return Double.isNaN(b0.doubleValue());
  }

  /** SQL <code>IS_NAN</code> operator applied to double values. */
  public static boolean isNaN(double b0) {
    return Double.isNaN(b0);
  }

  /** SQL <code>IS_NAN</code> operator applied to float values. */
  public static boolean isNaN(float b0) {
    return Float.isNaN(b0);
  }

  // RADIANS
  /** SQL <code>RADIANS</code> operator applied to BigDecimal values. */
  public static double radians(BigDecimal b0) {
    return Math.toRadians(b0.doubleValue());
  }

  /** SQL <code>RADIANS</code> operator applied to double values. */
  public static double radians(double b0) {
    return Math.toRadians(b0);
  }

  /** SQL <code>SECH</code> operator applied to BigDecimal values. */
  public static double sech(BigDecimal b0) {
    return 1.0d / Math.cosh(b0.doubleValue());
  }

  /** SQL <code>SECH</code> operator applied to double values. */
  public static double sech(double b0) {
    return 1.0d / Math.cosh(b0);
  }

  // SQL ROUND
  /** SQL <code>ROUND</code> operator applied to int values. */
  public static int sround(int b0) {
    return sround(b0, 0);
  }

  /** SQL <code>ROUND</code> operator applied to int values. */
  public static int sround(int b0, int b1) {
    return sround(BigDecimal.valueOf(b0), b1).intValue();
  }

  /** SQL <code>ROUND</code> operator applied to long values. */
  public static long sround(long b0) {
    return sround(b0, 0);
  }

  /** SQL <code>ROUND</code> operator applied to long values. */
  public static long sround(long b0, int b1) {
    return sround(BigDecimal.valueOf(b0), b1).longValue();
  }

  /** SQL <code>ROUND</code> operator applied to BigDecimal values. */
  public static BigDecimal sround(BigDecimal b0) {
    return sround(b0, 0);
  }

  /** SQL <code>ROUND</code> operator applied to BigDecimal values. */
  public static BigDecimal sround(BigDecimal b0, int b1) {
    return b0.movePointRight(b1)
        .setScale(0, RoundingMode.HALF_UP).movePointLeft(b1);
  }

  /** SQL <code>ROUND</code> operator applied to double values. */
  public static double sround(double b0) {
    return sround(b0, 0);
  }

  /** SQL <code>ROUND</code> operator applied to double values. */
  public static double sround(double b0, int b1) {
    return sround(BigDecimal.valueOf(b0), b1).doubleValue();
  }

  // SQL TRUNCATE
  /** SQL <code>TRUNCATE</code> operator applied to int values. */
  public static int struncate(int b0) {
    return struncate(b0, 0);
  }

  public static int struncate(int b0, int b1) {
    return struncate(BigDecimal.valueOf(b0), b1).intValue();
  }

  /** SQL <code>TRUNCATE</code> operator applied to long values. */
  public static long struncate(long b0) {
    return struncate(b0, 0);
  }

  public static long struncate(long b0, int b1) {
    return struncate(BigDecimal.valueOf(b0), b1).longValue();
  }

  /** SQL <code>TRUNCATE</code> operator applied to BigDecimal values. */
  public static BigDecimal struncate(BigDecimal b0) {
    return struncate(b0, 0);
  }

  public static BigDecimal struncate(BigDecimal b0, int b1) {
    return b0.movePointRight(b1)
        .setScale(0, RoundingMode.DOWN).movePointLeft(b1);
  }

  /** SQL <code>TRUNCATE</code> operator applied to double values. */
  public static double struncate(double b0) {
    return struncate(b0, 0);
  }

  public static double struncate(double b0, int b1) {
    return struncate(BigDecimal.valueOf(b0), b1).doubleValue();
  }

  // SIGN
  /** SQL <code>SIGN</code> operator applied to int values. */
  public static int sign(int b0) {
    return Integer.signum(b0);
  }

  /** SQL <code>SIGN</code> operator applied to long values. */
  public static long sign(long b0) {
    return Long.signum(b0);
  }

  /** SQL <code>SIGN</code> operator applied to BigDecimal values. */
  public static BigDecimal sign(BigDecimal b0) {
    return BigDecimal.valueOf(b0.signum());
  }

  /** SQL <code>SIGN</code> operator applied to double values. */
  public static double sign(double b0) {
    return Math.signum(b0);
  }

  // SIN
  /** SQL <code>SIN</code> operator applied to BigDecimal values. */
  public static double sin(BigDecimal b0) {
    return Math.sin(b0.doubleValue());
  }

  /** SQL <code>SIN</code> operator applied to double values. */
  public static double sin(double b0) {
    return Math.sin(b0);
  }

  // SINH
  /** SQL <code>SINH</code> operator applied to BigDecimal values. */
  public static double sinh(BigDecimal b) {
    return sinh(b.doubleValue());
  }

  /** SQL <code>SINH</code> operator applied to double values. */
  public static double sinh(double b) {
    return Math.sinh(b);
  }

  // TAN
  /** SQL <code>TAN</code> operator applied to BigDecimal values. */
  public static double tan(BigDecimal b0) {
    return Math.tan(b0.doubleValue());
  }

  /** SQL <code>TAN</code> operator applied to double values. */
  public static double tan(double b0) {
    return Math.tan(b0);
  }

  // TANH
  /** SQL <code>TANH</code> operator applied to BigDecimal values. */
  public static double tanh(BigDecimal b) {
    return tanh(b.doubleValue());
  }

  /** SQL <code>TANH</code> operator applied to double values. */
  public static double tanh(double b) {
    return Math.tanh(b);
  }

  // CSC
  /** SQL <code>CSC</code> operator applied to BigDecimal values. */
  public static double csc(BigDecimal b0) {
    return 1.0d / Math.sin(b0.doubleValue());
  }

  /** SQL <code>CSC</code> operator applied to double values. */
  public static double csc(double b0) {
    return 1.0d / Math.sin(b0);
  }

  // SEC
  /** SQL <code>SEC</code> operator applied to BigDecimal values. */
  public static double sec(BigDecimal b0) {
    return 1.0d / Math.cos(b0.doubleValue());
  }

  /** SQL <code>SEC</code> operator applied to double values. */
  public static double sec(double b0) {
    return 1.0d / Math.cos(b0);
  }

  // Helpers

  /** Helper for implementing MIN. Somewhat similar to LEAST operator. */
  public static <T extends Comparable<T>> T lesser(T b0, T b1) {
    return b0 == null || b0.compareTo(b1) > 0 ? b1 : b0;
  }

  /** LEAST operator. */
  public static <T extends Comparable<T>> T least(T b0, T b1) {
    return b0 == null || b1 != null && b0.compareTo(b1) > 0 ? b1 : b0;
  }

  public static boolean greater(boolean b0, boolean b1) {
    return b0 || b1;
  }

  public static boolean lesser(boolean b0, boolean b1) {
    return b0 && b1;
  }

  public static byte greater(byte b0, byte b1) {
    return b0 > b1 ? b0 : b1;
  }

  public static byte lesser(byte b0, byte b1) {
    return b0 > b1 ? b1 : b0;
  }

  public static char greater(char b0, char b1) {
    return b0 > b1 ? b0 : b1;
  }

  public static char lesser(char b0, char b1) {
    return b0 > b1 ? b1 : b0;
  }

  public static short greater(short b0, short b1) {
    return b0 > b1 ? b0 : b1;
  }

  public static short lesser(short b0, short b1) {
    return b0 > b1 ? b1 : b0;
  }

  public static int greater(int b0, int b1) {
    return b0 > b1 ? b0 : b1;
  }

  public static int lesser(int b0, int b1) {
    return b0 > b1 ? b1 : b0;
  }

  public static long greater(long b0, long b1) {
    return b0 > b1 ? b0 : b1;
  }

  public static long lesser(long b0, long b1) {
    return b0 > b1 ? b1 : b0;
  }

  public static float greater(float b0, float b1) {
    return b0 > b1 ? b0 : b1;
  }

  public static float lesser(float b0, float b1) {
    return b0 > b1 ? b1 : b0;
  }

  public static double greater(double b0, double b1) {
    return b0 > b1 ? b0 : b1;
  }

  public static double lesser(double b0, double b1) {
    return b0 > b1 ? b1 : b0;
  }

  /** Helper for implementing MAX. Somewhat similar to GREATEST operator. */
  public static <T extends Comparable<T>> T greater(T b0, T b1) {
    return b0 == null || b0.compareTo(b1) < 0 ? b1 : b0;
  }

  /** GREATEST operator. */
  public static <T extends Comparable<T>> T greatest(T b0, T b1) {
    return b0 == null || b1 != null && b0.compareTo(b1) < 0 ? b1 : b0;
  }

  /** CAST(FLOAT AS VARCHAR). */
  public static String toString(float x) {
    if (x == 0) {
      return "0E0";
    }
    BigDecimal bigDecimal =
        new BigDecimal(x, MathContext.DECIMAL32).stripTrailingZeros();
    final String s = bigDecimal.toString();
    return PATTERN_0_STAR_E.matcher(s).replaceAll("E").replace("E+", "E");
  }

  /** CAST(DOUBLE AS VARCHAR). */
  public static String toString(double x) {
    if (x == 0) {
      return "0E0";
    }
    BigDecimal bigDecimal =
        new BigDecimal(x, MathContext.DECIMAL64).stripTrailingZeros();
    final String s = bigDecimal.toString();
    return PATTERN_0_STAR_E.matcher(s).replaceAll("E").replace("E+", "E");
  }

  /** CAST(DECIMAL AS VARCHAR). */
  public static String toString(BigDecimal x) {
    final String s = x.toString();
    if (s.equals("0")) {
      return s;
    } else if (s.startsWith("0.")) {
      // we want ".1" not "0.1"
      return s.substring(1);
    } else if (s.startsWith("-0.")) {
      // we want "-.1" not "-0.1"
      return "-" + s.substring(2);
    } else {
      return s;
    }
  }

  /** CAST(BOOLEAN AS VARCHAR). */
  public static String toString(boolean x) {
    // Boolean.toString returns lower case -- no good.
    return x ? "TRUE" : "FALSE";
  }

  @NonDeterministic
  private static Object cannotConvert(Object o, Class toType) {
    throw RESOURCE.cannotConvert(String.valueOf(o), toType.toString()).ex();
  }

  /** CAST(VARCHAR AS BOOLEAN). */
  public static boolean toBoolean(String s) {
    s = trim(true, true, " ", s);
    if (s.equalsIgnoreCase("TRUE")) {
      return true;
    } else if (s.equalsIgnoreCase("FALSE")) {
      return false;
    } else {
      throw RESOURCE.invalidCharacterForCast(s).ex();
    }
  }

  public static boolean toBoolean(Number number) {
    return !number.equals(0);
  }

  public static boolean toBoolean(Object o) {
    return o instanceof Boolean ? (Boolean) o
        : o instanceof Number ? toBoolean((Number) o)
        : o instanceof String ? toBoolean((String) o)
        : (Boolean) cannotConvert(o, boolean.class);
  }

  // Don't need parseByte etc. - Byte.parseByte is sufficient.

  public static byte toByte(Object o) {
    return o instanceof Byte ? (Byte) o
        : o instanceof Number ? toByte((Number) o)
        : Byte.parseByte(o.toString());
  }

  public static byte toByte(Number number) {
    return number.byteValue();
  }

  public static char toChar(String s) {
    return s.charAt(0);
  }

  public static Character toCharBoxed(String s) {
    return s.charAt(0);
  }

  public static short toShort(String s) {
    return Short.parseShort(s.trim());
  }

  public static short toShort(Number number) {
    return number.shortValue();
  }

  public static short toShort(Object o) {
    return o instanceof Short ? (Short) o
        : o instanceof Number ? toShort((Number) o)
        : o instanceof String ? toShort((String) o)
        : (Short) cannotConvert(o, short.class);
  }

  /**
   * Converts a SQL DATE value from the Java type
   * ({@link java.sql.Date}) to the internal representation type
   * (number of days since January 1st, 1970 as {@code int})
   * in the local time zone.
   *
   * <p>Since a time zone is not available, the date is converted to represent
   * the same date as a Unix date in UTC as the {@link java.sql.Date} value in
   * the local time zone.
   *
   * @see #toInt(java.sql.Date, TimeZone)
   * @see #internalToDate(int) converse method
   */
  public static int toInt(java.sql.Date v) {
    return toInt(v, LOCAL_TZ);
  }

  /**
   * Converts a SQL DATE value from the Java type
   * ({@link java.sql.Date}) to the internal representation type
   * (number of days since January 1st, 1970 as {@code int}).
   *
   * <p>The {@link java.sql.Date} class uses the standard Gregorian calendar
   * which switches from the Julian calendar to the Gregorian calendar in
   * October 1582. For compatibility with ISO-8601, the internal representation
   * is converted to use the proleptic Gregorian calendar.
   *
   * <p>If the date contains a partial day, it will be rounded to a full day
   * depending on the milliseconds value. If the milliseconds value is positive,
   * it will be rounded down to the closest full day. If the milliseconds value
   * is negative, it will be rounded up to the closest full day.
   */
  public static int toInt(java.sql.Date v, TimeZone timeZone) {
    return DateTimeUtils.sqlDateToUnixDate(v, timeZone);
  }

  /**
   * Converts a nullable SQL DATE value from the Java type
   * ({@link java.sql.Date}) to the internal representation type
   * (number of days since January 1st, 1970 as {@link Integer})
   * in the local time zone.
   *
   * <p>Since a time zone is not available, the date is converted to represent
   * the same date as a Unix date in UTC as the {@link java.sql.Date} value in
   * the local time zone.
   *
   * @see #toInt(java.sql.Date, TimeZone)
   * @see #internalToDate(Integer) converse method
   */
  public static @PolyNull Integer toIntOptional(java.sql.@PolyNull Date v) {
    return v == null
        ? castNonNull(null)
        : toInt(v);
  }

  /**
   * Converts a nullable SQL DATE value from the Java type
   * ({@link java.sql.Date}) to the internal representation type
   * (number of days since January 1st, 1970 as {@link Integer}).
   *
   * @see #toInt(java.sql.Date, TimeZone)
   */
  public static @PolyNull Integer toIntOptional(java.sql.@PolyNull Date v,
      TimeZone timeZone) {
    return v == null
        ? castNonNull(null)
        : toInt(v, timeZone);
  }

  /**
   * Converts a SQL TIME value from the Java type
   * ({@link java.sql.Time}) to the internal representation type
   * (number of milliseconds since January 1st, 1970 as {@code int})
   * in the local time zone.
   *
   * @see #toIntOptional(java.sql.Time)
   * @see #internalToTime(int) converse method
   */
  public static int toInt(java.sql.Time v) {
    return DateTimeUtils.sqlTimeToUnixTime(v, LOCAL_TZ);
  }

  /**
   * Converts a nullable SQL TIME value from the Java type
   * ({@link java.sql.Time}) to the internal representation type
   * (number of milliseconds since January 1st, 1970 as {@link Integer}).
   *
   * @see #toInt(java.sql.Time)
   * @see #internalToTime(Integer) converse method
   */
  public static @PolyNull Integer toIntOptional(java.sql.@PolyNull Time v) {
    return v == null ? castNonNull(null) : toInt(v);
  }

  public static int toInt(String s) {
    return Integer.parseInt(s.trim());
  }

  public static int toInt(Number number) {
    return number.intValue();
  }

  public static int toInt(Object o) {
    return o instanceof Integer ? (Integer) o
        : o instanceof Number ? toInt((Number) o)
        : o instanceof String ? toInt((String) o)
        : o instanceof java.sql.Date ? toInt((java.sql.Date) o)
        : o instanceof java.sql.Time ? toInt((java.sql.Time) o)
        : (Integer) cannotConvert(o, int.class);
  }

  public static @PolyNull Integer toIntOptional(@PolyNull Object o) {
    return o == null ? castNonNull(null) : toInt(o);
  }

  /**
   * Converts a SQL TIMESTAMP value from the Java type
   * ({@link java.util.Date}) to the internal representation type
   * (number of milliseconds since January 1st, 1970 as {@code long}).
   *
   * <p>Since a time zone is not available, converts the timestamp to represent
   * the same date and time as a Unix timestamp in UTC as the
   * {@link java.util.Date} value in the local time zone.
   *
   * <p>The {@link java.util.Date} class uses the standard Gregorian calendar
   * which switches from the Julian calendar to the Gregorian calendar in
   * October 1582. For compatibility with ISO-8601, converts the internal
   * representation to use the proleptic Gregorian calendar.
   */
  public static long toLong(java.util.Date v) {
    return DateTimeUtils.utilDateToUnixTimestamp(v, LOCAL_TZ);
  }

  /**
   * Converts a SQL TIMESTAMP value from the Java type
   * ({@link Timestamp}) to the internal representation type
   * (number of milliseconds since January 1st, 1970 as {@code long}).
   *
   * <p>Since a time zone is not available, converts the timestamp to represent
   * the same date and time as a Unix timestamp in UTC as the
   * {@link Timestamp} value in the local time zone.
   *
   * @see #toLong(Timestamp, TimeZone)
   * @see #internalToTimestamp(Long) converse method
   */
  public static long toLong(Timestamp v) {
    return toLong(v, LOCAL_TZ);
  }

  /**
   * Converts a SQL TIMESTAMP value from the Java type
   * ({@link Timestamp}) to the internal representation type
   * (number of milliseconds since January 1st, 1970 as {@code long}).
   *
   * <p>For backwards compatibility, time zone offsets are calculated in
   * relation to the local time zone instead of UTC. Providing the default time
   * zone or {@code null} will return the timestamp unmodified.
   *
   * <p>The {@link Timestamp} class uses the standard Gregorian calendar which
   * switches from the Julian calendar to the Gregorian calendar in
   * October 1582. For compatibility with ISO-8601, the internal representation
   * is converted to use the proleptic Gregorian calendar.
   */
  public static long toLong(Timestamp v, TimeZone timeZone) {
    return DateTimeUtils.sqlTimestampToUnixTimestamp(v, timeZone);
  }

  /**
   * Converts a nullable SQL TIMESTAMP value from the Java type
   * ({@link Timestamp}) to the internal representation type
   * (number of milliseconds since January 1st, 1970 as {@link Long})
   * in the local time zone.
   *
   * @see #toLong(Timestamp, TimeZone)
   * @see #internalToTimestamp(Long) converse method
   */
  public static @PolyNull Long toLongOptional(@PolyNull Timestamp v) {
    return v == null ? castNonNull(null) : toLong(v, LOCAL_TZ);
  }

  /**
   * Converts a nullable SQL TIMESTAMP value from the Java type
   * ({@link Timestamp}) to the internal representation type
   * (number of milliseconds since January 1st, 1970 as {@link Long}).
   *
   * @see #toLong(Timestamp, TimeZone)
   */
  public static @PolyNull Long toLongOptional(@PolyNull Timestamp v,
      TimeZone timeZone) {
    if (v == null) {
      return castNonNull(null);
    }
    return toLong(v, timeZone);
  }

  public static long toLong(String s) {
    if (s.startsWith("199") && s.contains(":")) {
      return Timestamp.valueOf(s).getTime();
    }
    return Long.parseLong(s.trim());
  }

  public static long toLong(Number number) {
    return number.longValue();
  }

  public static long toLong(Object o) {
    return o instanceof Long ? (Long) o
        : o instanceof Number ? toLong((Number) o)
        : o instanceof String ? toLong((String) o)
        : o instanceof java.sql.Date ? toInt((java.sql.Date) o)
        : o instanceof java.sql.Time ? toInt((java.sql.Time) o)
        : o instanceof java.sql.Timestamp ? toLong((java.sql.Timestamp) o)
        : o instanceof java.util.Date ? toLong((java.util.Date) o)
        : (Long) cannotConvert(o, long.class);
  }

  public static @PolyNull Long toLongOptional(@PolyNull Object o) {
    return o == null ? castNonNull(null) : toLong(o);
  }

  public static float toFloat(String s) {
    return Float.parseFloat(s.trim());
  }

  public static float toFloat(Number number) {
    return number.floatValue();
  }

  public static float toFloat(Object o) {
    return o instanceof Float ? (Float) o
        : o instanceof Number ? toFloat((Number) o)
        : o instanceof String ? toFloat((String) o)
        : (Float) cannotConvert(o, float.class);
  }

  public static double toDouble(String s) {
    return Double.parseDouble(s.trim());
  }

  public static double toDouble(Number number) {
    return number.doubleValue();
  }

  public static double toDouble(Object o) {
    return o instanceof Double ? (Double) o
        : o instanceof Number ? toDouble((Number) o)
        : o instanceof String ? toDouble((String) o)
        : (Double) cannotConvert(o, double.class);
  }

  public static BigDecimal toBigDecimal(String s) {
    return new BigDecimal(s.trim());
  }

  public static BigDecimal toBigDecimal(Number number) {
    // There are some values of "long" that cannot be represented as "double".
    // Not so "int". If it isn't a long, go straight to double.
    return number instanceof BigDecimal ? (BigDecimal) number
        : number instanceof BigInteger ? new BigDecimal((BigInteger) number)
        : number instanceof Long ? new BigDecimal(number.longValue())
        : new BigDecimal(number.doubleValue());
  }

  public static BigDecimal toBigDecimal(Object o) {
    return o instanceof Number ? toBigDecimal((Number) o)
        : toBigDecimal(o.toString());
  }

  /**
   * Converts a SQL DATE value from the internal representation type
   * (number of days since January 1st, 1970) to the Java type
   * ({@link java.sql.Date}).
   *
   * <p>Since a time zone is not available, converts the date to represent the
   * same date as a {@link java.sql.Date} in the local time zone as the Unix
   * date in UTC.
   *
   * <p>The Unix date should be the number of days since January 1st, 1970
   * using the proleptic Gregorian calendar as defined by ISO-8601. The
   * returned {@link java.sql.Date} object will use the standard Gregorian
   * calendar which switches from the Julian calendar to the Gregorian calendar
   * in October 1582.
   *
   * @see #internalToDate(Integer)
   * @see #toInt(java.sql.Date) converse method
   */
  public static java.sql.Date internalToDate(int v) {
    final LocalDate date = LocalDate.ofEpochDay(v);
    return java.sql.Date.valueOf(date);
  }

  /**
   * Converts a nullable SQL DATE value from the internal representation type
   * (number of days since January 1st, 1970) to the Java type
   * ({@link java.sql.Date}).
   *
   * @see #internalToDate(int)
   * @see #toIntOptional(java.sql.Date) converse method
   */
  public static java.sql.@PolyNull Date internalToDate(@PolyNull Integer v) {
    return v == null ? castNonNull(null) : internalToDate(v.intValue());
  }

  /**
   * Converts a SQL TIME value from the internal representation type
   * (number of milliseconds since January 1st, 1970) to the Java type
   * ({@link java.sql.Time}).
   *
   * @see #internalToTime(Integer)
   * @see #toInt(java.sql.Time) converse method
   */
  public static java.sql.Time internalToTime(int v) {
    return new java.sql.Time(v - LOCAL_TZ.getOffset(v));
  }

  /**
   * Converts a nullable SQL TIME value from the internal representation type
   * (number of milliseconds since January 1st, 1970) to the Java type
   * ({@link java.sql.Time}).
   *
   * @see #internalToTime(Integer)
   * @see #toIntOptional(java.sql.Time) converse method
   */
  public static java.sql.@PolyNull Time internalToTime(@PolyNull Integer v) {
    return v == null ? castNonNull(null) : internalToTime(v.intValue());
  }

  public static @PolyNull Integer toTimeWithLocalTimeZone(@PolyNull String v) {
    if (v == null) {
      return castNonNull(null);
    }
    return new TimeWithTimeZoneString(v)
        .withTimeZone(DateTimeUtils.UTC_ZONE)
        .getLocalTimeString()
        .getMillisOfDay();
  }

  public static @PolyNull Integer toTimeWithLocalTimeZone(@PolyNull String v,
      TimeZone timeZone) {
    if (v == null) {
      return castNonNull(null);
    }
    return new TimeWithTimeZoneString(v + " " + timeZone.getID())
        .withTimeZone(DateTimeUtils.UTC_ZONE)
        .getLocalTimeString()
        .getMillisOfDay();
  }

  public static int timeWithLocalTimeZoneToTime(int v, TimeZone timeZone) {
    return TimeWithTimeZoneString.fromMillisOfDay(v)
        .withTimeZone(timeZone)
        .getLocalTimeString()
        .getMillisOfDay();
  }

  public static long timeWithLocalTimeZoneToTimestamp(String date, int v, TimeZone timeZone) {
    final TimeWithTimeZoneString tTZ = TimeWithTimeZoneString.fromMillisOfDay(v)
        .withTimeZone(DateTimeUtils.UTC_ZONE);
    return new TimestampWithTimeZoneString(date + " " + tTZ.toString())
        .withTimeZone(timeZone)
        .getLocalTimestampString()
        .getMillisSinceEpoch();
  }

  public static long timeWithLocalTimeZoneToTimestampWithLocalTimeZone(String date, int v) {
    final TimeWithTimeZoneString tTZ = TimeWithTimeZoneString.fromMillisOfDay(v)
        .withTimeZone(DateTimeUtils.UTC_ZONE);
    return new TimestampWithTimeZoneString(date + " " + tTZ.toString())
        .getLocalTimestampString()
        .getMillisSinceEpoch();
  }

  public static String timeWithLocalTimeZoneToString(int v, TimeZone timeZone) {
    return TimeWithTimeZoneString.fromMillisOfDay(v)
        .withTimeZone(timeZone)
        .toString();
  }

  /** State for {@code FORMAT_DATE}, {@code FORMAT_TIMESTAMP},
   * {@code FORMAT_DATETIME}, {@code FORMAT_TIME}, {@code TO_CHAR} functions. */
  @Deterministic
  public static class DateFormatFunction {
    /** Work space for various functions. Clear it before you use it. */
    final StringBuilder sb = new StringBuilder();

    /** Cache key. */
    private static class Key extends MapEntry<FormatModel, String> {
      Key(FormatModel formatModel, String format) {
        super(formatModel, format);
      }
    }

    private final LoadingCache<Key, List<FormatElement>> formatCache =
        CacheBuilder.newBuilder()
            .maximumSize(FUNCTION_LEVEL_CACHE_MAX_SIZE.value())
            .build(CacheLoader.from(key -> key.t.parseNoCache(key.u)));

    /** Given a format string and a format model, calls an action with the
     * list of elements obtained by parsing that format string. */
    protected final void withElements(FormatModel formatModel, String format,
        Consumer<List<FormatElement>> consumer) {
      List<FormatElement> elements =
          formatCache.getUnchecked(new Key(formatModel, format));
      consumer.accept(elements);
    }

    private String internalFormatDatetime(String fmtString,
        java.util.Date date) {
      sb.setLength(0);
      withElements(FormatModels.BIG_QUERY, fmtString, elements ->
          elements.forEach(element -> element.format(sb, date)));
      return sb.toString();
    }

    public String formatTimestamp(DataContext ctx, String fmtString,
        long timestamp) {
      return internalFormatDatetime(fmtString, internalToTimestamp(timestamp));
    }

    public String toChar(long timestamp, String pattern) {
      final Timestamp sqlTimestamp = internalToTimestamp(timestamp);
      sb.setLength(0);
      withElements(FormatModels.POSTGRESQL, pattern, elements ->
          elements.forEach(element -> element.format(sb, sqlTimestamp)));
      return sb.toString().trim();
    }

    public String formatDate(DataContext ctx, String fmtString, int date) {
      return internalFormatDatetime(fmtString, internalToDate(date));
    }

    public String formatTime(DataContext ctx, String fmtString, int time) {
      return internalFormatDatetime(fmtString, internalToTime(time));
    }
  }

  /** State for {@code PARSE_DATE}, {@code PARSE_TIMESTAMP},
   * {@code PARSE_DATETIME}, {@code PARSE_TIME} functions. */
  @Deterministic
  public static class DateParseFunction {
    /** Use a {@link DateFormatFunction} for its cache of parsed
     * format strings. */
    final DateFormatFunction f = new DateFormatFunction();

    private final LoadingCache<Key, DateFormat> cache =
        CacheBuilder.newBuilder()
            .maximumSize(FUNCTION_LEVEL_CACHE_MAX_SIZE.value())
            .build(CacheLoader.from(key -> key.toDateFormat(f)));

    private <T> T withParser(String fmt, String timeZone,
        Function<DateFormat, T> action) {
      final DateFormat dateFormat = cache.getUnchecked(new Key(fmt, timeZone));
      return action.apply(dateFormat);
    }

    private long internalParseDatetime(String fmtString, String datetime) {
      return internalParseDatetime(fmtString, datetime,
          DateTimeUtils.DEFAULT_ZONE.getID());
    }

    private long internalParseDatetime(String fmt, String datetime,
        String timeZone) {
      final ParsePosition pos = new ParsePosition(0);
      Date parsed =
          withParser(fmt, timeZone, parser -> parser.parse(datetime, pos));
      // Throw if either the parse was unsuccessful, or the format string did
      // not contain enough elements to parse the datetime string completely.
      if (pos.getErrorIndex() >= 0 || pos.getIndex() != datetime.length()) {
        SQLException e =
            new SQLException(
                String.format(Locale.ROOT,
                    "Invalid format: '%s' for datetime string: '%s'.", fmt,
                    datetime));
        throw Util.toUnchecked(e);
      }
      // Suppress the Errorprone warning "[JavaUtilDate] Date has a bad API that
      // leads to bugs; prefer java.time.Instant or LocalDate" because we know
      // what we're doing.
      @SuppressWarnings("JavaUtilDate")
      final long millisSinceEpoch = parsed.getTime();
      return millisSinceEpoch;
    }

    public int parseDate(String fmtString, String date) {
      final long millisSinceEpoch = internalParseDatetime(fmtString, date);
      return toInt(new java.sql.Date(millisSinceEpoch));
    }

    public long parseDatetime(String fmtString, String datetime) {
      final long millisSinceEpoch = internalParseDatetime(fmtString, datetime);
      return toLong(new Timestamp(millisSinceEpoch));
    }

    public int parseTime(String fmtString, String time) {
      final long millisSinceEpoch = internalParseDatetime(fmtString, time);
      return toInt(new Time(millisSinceEpoch));
    }

    public long parseTimestamp(String fmtString, String timestamp) {
      return parseTimestamp(fmtString, timestamp, "UTC");
    }

    public long parseTimestamp(String fmtString, String timestamp,
        String timeZone) {
      TimeZone tz = TimeZone.getTimeZone(timeZone);
      final long millisSinceEpoch =
          internalParseDatetime(fmtString, timestamp, timeZone);
      return toLong(new java.sql.Timestamp(millisSinceEpoch), tz);
    }

    /** Key for cache of parsed format strings. */
    private static final class Key {
      final String fmt;
      final String timeZone;

      Key(String fmt, String timeZone) {
        this.fmt = fmt;
        this.timeZone = timeZone;
      }

      @Override public int hashCode() {
        return fmt.hashCode()
            + timeZone.hashCode() * 37;
      }

      @Override public boolean equals(@Nullable Object obj) {
        return this == obj
            || obj instanceof Key
            && fmt.equals(((Key) obj).fmt)
            && timeZone.equals(((Key) obj).timeZone);
      }

      DateFormat toDateFormat(DateFormatFunction f) {
        f.sb.setLength(0);
        f.withElements(FormatModels.BIG_QUERY, fmt, elements ->
            elements.forEach(ele -> ele.toPattern(f.sb)));
        final String javaFmt = f.sb.toString();

        // TODO: make Locale configurable. ENGLISH set for weekday
        // parsing (e.g. Thursday, Friday).
        final DateFormat parser =
            new SimpleDateFormat(javaFmt, Locale.ENGLISH);
        parser.setLenient(false);
        TimeZone tz = TimeZone.getTimeZone(timeZone);
        parser.setCalendar(Calendar.getInstance(tz, Locale.ROOT));
        return parser;
      }
    }
  }

  /**
   * Converts a SQL TIMESTAMP value from the internal representation type
   * (number of milliseconds since January 1st, 1970) to the Java Type
   * ({@link Timestamp})
   * in the local time zone.
   *
   * <p>Since a time zone is not available, the timestamp is converted to
   * represent the same timestamp as a {@link Timestamp} in the local time zone
   * as the Unix timestamp in UTC.
   *
   * <p>The Unix timestamp should be the number of milliseconds since
   * January 1st, 1970 using the proleptic Gregorian calendar as defined by
   * ISO-8601. The returned {@link Timestamp} object will use the standard
   * Gregorian calendar which switches from the Julian calendar to the
   * Gregorian calendar in October 1582.
   *
   * @see #internalToTimestamp(Long)
   * @see #toLong(Timestamp, TimeZone)
   * @see #toLongOptional(Timestamp)
   * @see #toLongOptional(Timestamp, TimeZone)
   * @see #toLong(Timestamp) converse method
   */
  public static java.sql.Timestamp internalToTimestamp(long v) {
    final LocalDateTime dateTime =
        LocalDateTime.ofEpochSecond(
            Math.floorDiv(v, DateTimeUtils.MILLIS_PER_SECOND),
            (int) (Math.floorMod(v, DateTimeUtils.MILLIS_PER_SECOND)
                * DateTimeUtils.NANOS_PER_MILLI),
            ZoneOffset.UTC);
    return java.sql.Timestamp.valueOf(dateTime);
  }

  /**
   * Converts a nullable SQL TIMESTAMP value from the internal representation
   * type (number of milliseconds since January 1st, 1970) to the Java Type
   * ({@link Timestamp})
   * in the local time zone.
   *
   * @see #internalToTimestamp(long)
   * @see #toLong(Timestamp)
   * @see #toLong(Timestamp, TimeZone)
   * @see #toLongOptional(Timestamp, TimeZone)
   * @see #toLongOptional(Timestamp) converse method
   */
  public static java.sql.@PolyNull Timestamp internalToTimestamp(@PolyNull Long v) {
    return v == null ? castNonNull(null) : internalToTimestamp(v.longValue());
  }

  public static int timestampWithLocalTimeZoneToDate(long v, TimeZone timeZone) {
    return TimestampWithTimeZoneString.fromMillisSinceEpoch(v)
        .withTimeZone(timeZone)
        .getLocalDateString()
        .getDaysSinceEpoch();
  }

  public static int timestampWithLocalTimeZoneToTime(long v, TimeZone timeZone) {
    return TimestampWithTimeZoneString.fromMillisSinceEpoch(v)
        .withTimeZone(timeZone)
        .getLocalTimeString()
        .getMillisOfDay();
  }

  public static long timestampWithLocalTimeZoneToTimestamp(long v, TimeZone timeZone) {
    return TimestampWithTimeZoneString.fromMillisSinceEpoch(v)
        .withTimeZone(timeZone)
        .getLocalTimestampString()
        .getMillisSinceEpoch();
  }

  public static String timestampWithLocalTimeZoneToString(long v, TimeZone timeZone) {
    return TimestampWithTimeZoneString.fromMillisSinceEpoch(v)
        .withTimeZone(timeZone)
        .toString();
  }

  public static int timestampWithLocalTimeZoneToTimeWithLocalTimeZone(long v) {
    return TimestampWithTimeZoneString.fromMillisSinceEpoch(v)
        .getLocalTimeString()
        .getMillisOfDay();
  }

  /** For {@link SqlLibraryOperators#TIMESTAMP_SECONDS}. */
  public static long timestampSeconds(long v) {
    return v * 1000;
  }

  /** For {@link SqlLibraryOperators#TIMESTAMP_MILLIS}. */
  public static long timestampMillis(long v) {
    // translation is trivial, because Calcite represents TIMESTAMP values as
    // millis since epoch
    return v;
  }

  /** For {@link SqlLibraryOperators#TIMESTAMP_MICROS}. */
  public static long timestampMicros(long v) {
    return v / 1000;
  }

  /** For {@link SqlLibraryOperators#UNIX_SECONDS}. */
  public static long unixSeconds(long v) {
    return v / 1000;
  }

  /** For {@link SqlLibraryOperators#UNIX_MILLIS}. */
  public static long unixMillis(long v) {
    // translation is trivial, because Calcite represents TIMESTAMP values as
    // millis since epoch
    return v;
  }

  /** For {@link SqlLibraryOperators#UNIX_MICROS}. */
  public static long unixMicros(long v) {
    return v * 1000;
  }

  /** For {@link SqlLibraryOperators#DATE_FROM_UNIX_DATE}. */
  public static int dateFromUnixDate(int v) {
    // translation is trivial, because Calcite represents dates as Unix integers
    return v;
  }

  /** For {@link SqlLibraryOperators#UNIX_DATE}. */
  public static int unixDate(int v) {
    // translation is trivial, because Calcite represents dates as Unix integers
    return v;
  }

  /** SQL {@code DATE(year, month, day)} function. */
  public static int date(int year, int month, int day) {
    // Calcite represents dates as Unix integers (days since epoch).
    return (int) LocalDate.of(year, month, day).toEpochDay();
  }

  /** SQL {@code DATE(TIMESTAMP)} and
   * {@code DATE(TIMESTAMP WITH LOCAL TIME ZONE)} functions. */
  public static int date(long timestampMillis) {
    // Calcite represents dates as Unix integers (days since epoch).
    // Unix time ignores leap seconds; every day has the exact same number of
    // milliseconds. BigQuery TIMESTAMP and DATETIME values (Calcite TIMESTAMP
    // WITH LOCAL TIME ZONE and TIMESTAMP, respectively) are represented
    // internally as milliseconds since epoch (or epoch UTC).
    return (int) (timestampMillis / DateTimeUtils.MILLIS_PER_DAY);
  }

  /** SQL {@code DATE(TIMESTAMP WITH LOCAL TIME, timeZone)} function. */
  public static int date(long timestampMillis, String timeZone) {
    // Calcite represents dates as Unix integers (days since epoch).
    return (int) OffsetDateTime.ofInstant(Instant.ofEpochMilli(timestampMillis),
            ZoneId.of(timeZone))
        .toLocalDate()
        .toEpochDay();
  }

  /** SQL {@code DATETIME(<year>, <month>, <day>, <hour>, <minute>, <second>)}
   * function. */
  public static long datetime(int year, int month, int day, int hour,
      int minute, int second) {
    // BigQuery's DATETIME function returns a Calcite TIMESTAMP,
    // represented internally as milliseconds since epoch UTC.
    return LocalDateTime.of(year, month, day, hour, minute, second)
        .toEpochSecond(ZoneOffset.UTC)
        * DateTimeUtils.MILLIS_PER_SECOND;
  }

  /** SQL {@code DATETIME(DATE)} function; returns a Calcite TIMESTAMP. */
  public static long datetime(int daysSinceEpoch) {
    // BigQuery's DATETIME function returns a Calcite TIMESTAMP,
    // represented internally as milliseconds since epoch.
    return daysSinceEpoch * DateTimeUtils.MILLIS_PER_DAY;
  }

  /** SQL {@code DATETIME(DATE, TIME)} function; returns a Calcite TIMESTAMP. */
  public static long datetime(int daysSinceEpoch, int millisSinceMidnight) {
    // BigQuery's DATETIME function returns a Calcite TIMESTAMP,
    // represented internally as milliseconds since epoch UTC.
    return daysSinceEpoch * DateTimeUtils.MILLIS_PER_DAY + millisSinceMidnight;
  }

  /** SQL {@code DATETIME(TIMESTAMP WITH LOCAL TIME ZONE)} function;
   * returns a Calcite TIMESTAMP. */
  public static long datetime(long millisSinceEpoch) {
    // BigQuery TIMESTAMP and DATETIME values (Calcite TIMESTAMP WITH LOCAL TIME
    // ZONE and TIMESTAMP, respectively) are represented internally as
    // milliseconds since epoch (or epoch UTC).
    return millisSinceEpoch;
  }

  /** SQL {@code DATETIME(TIMESTAMP, timeZone)} function;
   * returns a Calcite TIMESTAMP. */
  public static long datetime(long millisSinceEpoch, String timeZone) {
    // BigQuery TIMESTAMP and DATETIME values (Calcite TIMESTAMP WITH LOCAL TIME
    // ZONE and TIMESTAMP, respectively) are represented internally as
    // milliseconds since epoch (or epoch UTC).
    return OffsetDateTime.ofInstant(Instant.ofEpochMilli(millisSinceEpoch),
            ZoneId.of(timeZone))
        .atZoneSimilarLocal(ZoneId.of("UTC"))
        .toInstant()
        .toEpochMilli();
  }

  /** SQL {@code TIMESTAMP(<string>)} function. */
  public static long timestamp(String expression) {
    // Calcite represents TIMESTAMP WITH LOCAL TIME ZONE as Unix integers
    // (milliseconds since epoch).
    return parseBigQueryTimestampLiteral(expression).toInstant().toEpochMilli();
  }

  /** SQL {@code TIMESTAMP(<string>, <timeZone>)} function. */
  public static long timestamp(String expression, String timeZone) {
    // Calcite represents TIMESTAMP WITH LOCAL TIME ZONE as Unix integers
    // (milliseconds since epoch).
    return parseBigQueryTimestampLiteral(expression)
        .atZoneSimilarLocal(ZoneId.of(timeZone))
        .toInstant()
        .toEpochMilli();
  }

  private static OffsetDateTime parseBigQueryTimestampLiteral(String expression) {
    // First try to parse with an offset, otherwise parse as a local and assume
    // UTC ("no offset").
    try {
      return OffsetDateTime.parse(expression,
          BIG_QUERY_TIMESTAMP_LITERAL_FORMATTER);
    } catch (DateTimeParseException e) {
      // ignore
    }
    if (IS_JDK_8
        && expression.matches(".*[+-][0-9][0-9]$")) {
      // JDK 8 has a bug that prevents matching offsets like "+00" but can
      // match "+00:00".
      try {
        expression += ":00";
        return OffsetDateTime.parse(expression,
            BIG_QUERY_TIMESTAMP_LITERAL_FORMATTER);
      } catch (DateTimeParseException e) {
        // ignore
      }
    }
    try {
      return LocalDateTime
          .parse(expression, BIG_QUERY_TIMESTAMP_LITERAL_FORMATTER)
          .atOffset(ZoneOffset.UTC);
    } catch (DateTimeParseException e2) {
      throw new IllegalArgumentException(
          String.format(Locale.ROOT,
              "Could not parse BigQuery timestamp literal: %s", expression),
          e2);
    }
  }

  /** SQL {@code TIMESTAMP(<date>)} function. */
  public static long timestamp(int days) {
    // Calcite represents TIMESTAMP WITH LOCAL TIME ZONE as Unix integers
    // (milliseconds since epoch). Unix time ignores leap seconds; every day
    // has the same number of milliseconds.
    return ((long) days) * DateTimeUtils.MILLIS_PER_DAY;
  }

  /** SQL {@code TIMESTAMP(<date>, <timeZone>)} function. */
  public static long timestamp(int days, String timeZone) {
    // Calcite represents TIMESTAMP WITH LOCAL TIME ZONE as Unix integers
    // (milliseconds since epoch).
    final LocalDateTime localDateTime =
        LocalDateTime.of(LocalDate.ofEpochDay(days), LocalTime.MIDNIGHT);
    final ZoneOffset zoneOffset =
        ZoneId.of(timeZone).getRules().getOffset(localDateTime);
    return OffsetDateTime.of(localDateTime, zoneOffset)
        .toInstant()
        .toEpochMilli();
  }

  /** SQL {@code TIMESTAMP(<timestamp>)} function; returns a TIMESTAMP WITH
   * LOCAL TIME ZONE. */
  public static long timestamp(long millisSinceEpoch) {
    // BigQuery TIMESTAMP and DATETIME values (Calcite TIMESTAMP WITH LOCAL
    // TIME ZONE and TIMESTAMP, respectively) are represented internally as
    // milliseconds since epoch UTC and epoch.
    return millisSinceEpoch;
  }

  /** SQL {@code TIMESTAMP(<timestamp>, <timeZone>)} function; returns a
   * TIMESTAMP WITH LOCAL TIME ZONE. */
  public static long timestamp(long millisSinceEpoch, String timeZone) {
    // BigQuery TIMESTAMP and DATETIME values (Calcite TIMESTAMP WITH LOCAL
    // TIME ZONE and TIMESTAMP, respectively) are represented internally as
    // milliseconds since epoch UTC and epoch.
    final Instant instant = Instant.ofEpochMilli(millisSinceEpoch);
    final ZoneId utcZone = ZoneId.of("UTC");
    return OffsetDateTime.ofInstant(instant, utcZone)
        .atZoneSimilarLocal(ZoneId.of(timeZone))
        .toInstant()
        .toEpochMilli();
  }

  /** SQL {@code TIME(<hour>, <minute>, <second>)} function. */
  public static int time(int hour, int minute, int second) {
    // Calcite represents time as Unix integers (milliseconds since midnight).
    return (int) (LocalTime.of(hour, minute, second).toSecondOfDay()
        * DateTimeUtils.MILLIS_PER_SECOND);
  }

  /** SQL {@code TIME(<timestamp>)} and {@code TIME(<timestampLtz>)}
   * functions. */
  public static int time(long timestampMillis) {
    // Calcite represents time as Unix integers (milliseconds since midnight).
    // Unix time ignores leap seconds; every day has the same number of
    // milliseconds.
    //
    // BigQuery TIMESTAMP and DATETIME values (Calcite TIMESTAMP WITH LOCAL
    // TIME ZONE and TIMESTAMP, respectively) are represented internally as
    // milliseconds since epoch UTC and epoch.
    return (int) (timestampMillis % DateTimeUtils.MILLIS_PER_DAY);
  }

  /** SQL {@code TIME(<timestampLtz>, <timeZone>)} function. */
  public static int time(long timestampMillis, String timeZone) {
    // Calcite represents time as Unix integers (milliseconds since midnight).
    // Unix time ignores leap seconds; every day has the same number of
    // milliseconds.
    final Instant instant = Instant.ofEpochMilli(timestampMillis);
    final ZoneId zoneId = ZoneId.of(timeZone);
    return (int) (OffsetDateTime.ofInstant(instant, zoneId)
        .toLocalTime()
        .toNanoOfDay()
        / (1000L * 1000L)); // milli > micro > nano
  }

  public static @PolyNull Long toTimestampWithLocalTimeZone(@PolyNull String v) {
    if (v == null) {
      return castNonNull(null);
    }
    return new TimestampWithTimeZoneString(v)
        .withTimeZone(DateTimeUtils.UTC_ZONE)
        .getLocalTimestampString()
        .getMillisSinceEpoch();
  }

  public static @PolyNull Long toTimestampWithLocalTimeZone(@PolyNull String v,
      TimeZone timeZone) {
    if (v == null) {
      return castNonNull(null);
    }
    return new TimestampWithTimeZoneString(v + " " + timeZone.getID())
        .withTimeZone(DateTimeUtils.UTC_ZONE)
        .getLocalTimestampString()
        .getMillisSinceEpoch();
  }

  // Don't need shortValueOf etc. - Short.valueOf is sufficient.

  /** Helper for CAST(... AS VARCHAR(maxLength)). */
  public static @PolyNull String truncate(@PolyNull String s, int maxLength) {
    if (s == null) {
      return s;
    } else if (s.length() > maxLength) {
      return s.substring(0, maxLength);
    } else {
      return s;
    }
  }

  /** Helper for CAST(... AS CHAR(maxLength)). */
  public static @PolyNull String truncateOrPad(@PolyNull String s, int maxLength) {
    if (s == null) {
      return s;
    } else {
      final int length = s.length();
      if (length > maxLength) {
        return s.substring(0, maxLength);
      } else {
        return length < maxLength ? Spaces.padRight(s, maxLength) : s;
      }
    }
  }

  /** Helper for CAST(... AS VARBINARY(maxLength)). */
  public static @PolyNull ByteString truncate(@PolyNull ByteString s, int maxLength) {
    if (s == null) {
      return s;
    } else if (s.length() > maxLength) {
      return s.substring(0, maxLength);
    } else {
      return s;
    }
  }

  /** Helper for CAST(... AS BINARY(maxLength)). */
  public static @PolyNull ByteString truncateOrPad(@PolyNull ByteString s, int maxLength) {
    if (s == null) {
      return s;
    } else {
      final int length = s.length();
      if (length > maxLength) {
        return s.substring(0, maxLength);
      } else if (length < maxLength) {
        return s.concat(new ByteString(new byte[maxLength - length]));
      } else {
        return s;
      }
    }
  }

  /** SQL {@code POSITION(seek IN string)} function. */
  public static int position(String seek, String s) {
    return s.indexOf(seek) + 1;
  }

  /** SQL {@code POSITION(seek IN string)} function for byte strings. */
  public static int position(ByteString seek, ByteString s) {
    return s.indexOf(seek) + 1;
  }

  /** SQL {@code POSITION(seek IN string FROM integer)} function. */
  public static int position(String seek, String s, int from) {
    if (from == 0) {
      throw RESOURCE.fromNotZero().ex();
    }
    if (from > 0) {
      return positionForwards(seek, s, from);
    } else {
      from += s.length(); // convert negative position to positive index
      return positionBackwards(seek, s, from);
    }
  }

  /** SQL {@code POSITION(seek IN string FROM integer)} function for byte
   * strings. */
  public static int position(ByteString seek, ByteString s, int from) {
    if (from == 0) {
      throw RESOURCE.fromNotZero().ex();
    }
    if (from > 0) {
      return positionForwards(seek, s, from);
    } else {
      from += s.length(); // convert negative position to 0-based index
      return positionBackwards(seek, s, from);
    }
  }

  /** Returns the position (1-based) of {@code seek} in string {@code s}
   * seeking forwards from {@code from} (1-based). */
  private static int positionForwards(String seek, String s, int from) {
    final int from0 = from - 1; // 0-based
    if (from0 >= s.length()) {
      return 0;
    } else {
      return s.indexOf(seek, from0) + 1;
    }
  }

  /** Returns the position (1-based) of {@code seek} in byte string {@code s}
   * seeking forwards from {@code from} (1-based). */
  private static int positionForwards(ByteString seek, ByteString s,
      int from) {
    final int from0 = from - 1; // 0-based
    if (from0 >= s.length()) {
      return 0;
    } else {
      return s.indexOf(seek, from0) + 1;
    }
  }

  /** Returns the position (1-based) of {@code seek} in string {@code s}
   * seeking backwards from {@code rightIndex} (0-based). */
  private static int positionBackwards(String seek, String s, int rightIndex) {
    if (rightIndex <= 0) {
      return 0;
    }
    int lastIndex = s.lastIndexOf(seek) + 1;
    while (lastIndex > rightIndex + 1) {
      lastIndex = s.substring(0, lastIndex - 1).lastIndexOf(seek) + 1;
      if (lastIndex == 0) {
        return 0;
      }
    }
    return lastIndex;
  }

  /** Returns the position (1-based) of {@code seek} in byte string {@code s}
   * seeking backwards from {@code rightIndex} (0-based). */
  private static int positionBackwards(ByteString seek, ByteString s,
      int rightIndex) {
    if (rightIndex <= 0) {
      return 0;
    }
    int lastIndex = 0;
    while (lastIndex < rightIndex) {
      // NOTE: When [CALCITE-5682] is fixed, use ByteString.lastIndexOf
      int indexOf = s.substring(lastIndex).indexOf(seek) + 1;
      if (indexOf == 0 || lastIndex + indexOf > rightIndex + 1) {
        break;
      }
      lastIndex += indexOf;
    }
    return lastIndex;
  }

  /** SQL {@code POSITION(seek, string, from, occurrence)} function. */
  public static int position(String seek, String s, int from, int occurrence) {
    if (from == 0) {
      throw RESOURCE.fromNotZero().ex();
    }
    if (occurrence == 0) {
      throw RESOURCE.occurrenceNotZero().ex();
    }
    if (from > 0) {
      // Forwards
      --from; // compensate for the '++from' 2 lines down
      for (int i = 0; i < occurrence; i++) {
        ++from; // move on to next occurrence
        from = positionForwards(seek, s, from);
        if (from == 0) {
          return 0;
        }
      }
    } else {
      // Backwards
      from += s.length() + 1; // convert negative position to positive index
      ++from; // compensate for the '--from' 2 lines down
      for (int i = 0; i < occurrence; i++) {
        --from; // move on to next occurrence
        from = positionBackwards(seek, s, from - 1);
        if (from == 0) {
          return 0;
        }
      }
    }
    return from;
  }

  /** SQL {@code POSITION(seek, string, from, occurrence)} function for byte
   * strings. */
  public static int position(ByteString seek, ByteString s, int from,
      int occurrence) {
    if (from == 0) {
      throw RESOURCE.fromNotZero().ex();
    }
    if (occurrence == 0) {
      throw RESOURCE.occurrenceNotZero().ex();
    }
    if (from > 0) {
      // Forwards
      --from; // compensate for the '++from' 2 lines down
      for (int i = 0; i < occurrence; i++) {
        ++from; // move on to next occurrence
        from = positionForwards(seek, s, from);
        if (from == 0) {
          return 0;
        }
      }
    } else {
      // Backwards
      from += s.length() + 1; // convert negative position to positive index
      ++from; // compensate for the '--from' 2 lines down
      for (int i = 0; i < occurrence; i++) {
        --from; // move on to next occurrence
        from = positionBackwards(seek, s, from - 1);
        if (from == 0) {
          return 0;
        }
      }
    }
    return from;
  }

  /** Helper for rounding. Truncate(12345, 1000) returns 12000. */
  public static long round(long v, long x) {
    return truncate(v + x / 2, x);
  }

  /** Helper for rounding. Truncate(12345, 1000) returns 12000. */
  public static long truncate(long v, long x) {
    long remainder = v % x;
    if (remainder < 0) {
      remainder += x;
    }
    return v - remainder;
  }

  /** Helper for rounding. Truncate(12345, 1000) returns 12000. */
  public static int round(int v, int x) {
    return truncate(v + x / 2, x);
  }

  /** Helper for rounding. Truncate(12345, 1000) returns 12000. */
  public static int truncate(int v, int x) {
    int remainder = v % x;
    if (remainder < 0) {
      remainder += x;
    }
    return v - remainder;
  }

  /**
   * SQL {@code DAYNAME} function, applied to a TIMESTAMP argument.
   *
   * @param timestamp Milliseconds from epoch
   * @param locale Locale
   * @return Name of the weekday in the given locale
   */
  public static String dayNameWithTimestamp(long timestamp, Locale locale) {
    return timeStampToLocalDate(timestamp)
        .format(ROOT_DAY_FORMAT.withLocale(locale));
  }

  /**
   * SQL {@code DAYNAME} function, applied to a DATE argument.
   *
   * @param date Days since epoch
   * @param locale Locale
   * @return Name of the weekday in the given locale
   */
  public static String dayNameWithDate(int date, Locale locale) {
    return dateToLocalDate(date)
        .format(ROOT_DAY_FORMAT.withLocale(locale));
  }

  /**
   * SQL {@code MONTHNAME} function, applied to a TIMESTAMP argument.
   *
   * @param timestamp Milliseconds from epoch
   * @param locale Locale
   * @return Name of the month in the given locale
   */
  public static String monthNameWithTimestamp(long timestamp, Locale locale) {
    return timeStampToLocalDate(timestamp)
        .format(ROOT_MONTH_FORMAT.withLocale(locale));
  }

  /**
   * SQL {@code MONTHNAME} function, applied to a DATE argument.
   *
   * @param date Days from epoch
   * @param locale Locale
   * @return Name of the month in the given locale
   */
  public static String monthNameWithDate(int date, Locale locale) {
    return dateToLocalDate(date)
        .format(ROOT_MONTH_FORMAT.withLocale(locale));
  }

  /**
   * Converts a date (days since epoch) to a {@link LocalDate}.
   *
   * @param date days since epoch
   * @return localDate
   */
  private static LocalDate dateToLocalDate(int date) {
    int y0 = (int) DateTimeUtils.unixDateExtract(TimeUnitRange.YEAR, date);
    int m0 = (int) DateTimeUtils.unixDateExtract(TimeUnitRange.MONTH, date);
    int d0 = (int) DateTimeUtils.unixDateExtract(TimeUnitRange.DAY, date);
    return LocalDate.of(y0, m0, d0);
  }

  /**
   * Converts a timestamp (milliseconds since epoch) to a {@link LocalDate}.
   *
   * @param timestamp milliseconds from epoch
   * @return localDate
   */
  private static LocalDate timeStampToLocalDate(long timestamp) {
    int date = timestampToDate(timestamp);
    return dateToLocalDate(date);
  }

  /** Converts a timestamp (milliseconds since epoch)
   * to a date (days since epoch). */
  public static int timestampToDate(long timestamp) {
    return (int) (timestamp / DateTimeUtils.MILLIS_PER_DAY);
  }

  /** Converts a timestamp (milliseconds since epoch)
   * to a time (milliseconds since midnight). */
  public static int timestampToTime(long timestamp) {
    return (int) (timestamp % DateTimeUtils.MILLIS_PER_DAY);
  }

  /** SQL {@code CURRENT_TIMESTAMP} function. */
  @NonDeterministic
  public static long currentTimestamp(DataContext root) {
    return DataContext.Variable.CURRENT_TIMESTAMP.get(root);
  }

  /** SQL {@code CURRENT_TIME} function. */
  @NonDeterministic
  public static int currentTime(DataContext root) {
    int time = timestampToTime(currentTimestamp(root));
    if (time < 0) {
      time = (int) (time + DateTimeUtils.MILLIS_PER_DAY);
    }
    return time;
  }

  /** SQL {@code CURRENT_DATE} function. */
  @NonDeterministic
  public static int currentDate(DataContext root) {
    final long timestamp = currentTimestamp(root);
    int date = timestampToDate(timestamp);
    final int time = timestampToTime(timestamp);
    if (time < 0) {
      --date;
    }
    return date;
  }

  /** SQL {@code LOCAL_TIMESTAMP} function. */
  @NonDeterministic
  public static long localTimestamp(DataContext root) {
    return DataContext.Variable.LOCAL_TIMESTAMP.get(root);
  }

  /** SQL {@code LOCAL_TIME} function. */
  @NonDeterministic
  public static int localTime(DataContext root) {
    return timestampToTime(localTimestamp(root));
  }

  @NonDeterministic
  public static TimeZone timeZone(DataContext root) {
    return DataContext.Variable.TIME_ZONE.get(root);
  }

  /** SQL {@code USER} function. */
  @Deterministic
  public static String user(DataContext root) {
    return requireNonNull(DataContext.Variable.USER.get(root));
  }

  /** SQL {@code SYSTEM_USER} function. */
  @Deterministic
  public static String systemUser(DataContext root) {
    return requireNonNull(DataContext.Variable.SYSTEM_USER.get(root));
  }

  @NonDeterministic
  public static Locale locale(DataContext root) {
    return DataContext.Variable.LOCALE.get(root);
  }

  /** SQL {@code DATEADD} function applied to a custom time frame.
   *
   * <p>Custom time frames are created as part of a {@link TimeFrameSet}.
   * This method retrieves the session's time frame set from the
   * {@link DataContext.Variable#TIME_FRAME_SET} variable, then looks up the
   * time frame by name. */
  public static int customDateAdd(DataContext root,
      String timeFrameName, int interval, int date) {
    final TimeFrameSet timeFrameSet =
        requireNonNull(DataContext.Variable.TIME_FRAME_SET.get(root));
    final TimeFrame timeFrame = timeFrameSet.get(timeFrameName);
    return timeFrameSet.addDate(date, interval, timeFrame);
  }

  /** SQL {@code TIMESTAMPADD} function applied to a custom time frame.
   *
   * <p>Custom time frames are created and accessed as described in
   * {@link #customDateAdd}. */
  public static long customTimestampAdd(DataContext root,
      String timeFrameName, long interval, long timestamp) {
    final TimeFrameSet timeFrameSet =
        requireNonNull(DataContext.Variable.TIME_FRAME_SET.get(root));
    final TimeFrame timeFrame = timeFrameSet.get(timeFrameName);
    return timeFrameSet.addTimestamp(timestamp, interval, timeFrame);
  }

  /** SQL {@code DATEDIFF} function applied to a custom time frame.
   *
   * <p>Custom time frames are created and accessed as described in
   * {@link #customDateAdd}. */
  public static int customDateDiff(DataContext root,
      String timeFrameName, int date, int date2) {
    final TimeFrameSet timeFrameSet =
        requireNonNull(DataContext.Variable.TIME_FRAME_SET.get(root));
    final TimeFrame timeFrame = timeFrameSet.get(timeFrameName);
    return timeFrameSet.diffDate(date, date2, timeFrame);
  }

  /** SQL {@code TIMESTAMPDIFF} function applied to a custom time frame.
   *
   * <p>Custom time frames are created and accessed as described in
   * {@link #customDateAdd}. */
  public static long customTimestampDiff(DataContext root,
      String timeFrameName, long timestamp, long timestamp2) {
    final TimeFrameSet timeFrameSet =
        requireNonNull(DataContext.Variable.TIME_FRAME_SET.get(root));
    final TimeFrame timeFrame = timeFrameSet.get(timeFrameName);
    return timeFrameSet.diffTimestamp(timestamp, timestamp2, timeFrame);
  }

  /** SQL {@code FLOOR} function applied to a {@code DATE} value
   * and a custom time frame.
   *
   * <p>Custom time frames are created and accessed as described in
   * {@link #customDateAdd}. */
  public static int customDateFloor(DataContext root,
      String timeFrameName, int date) {
    final TimeFrameSet timeFrameSet =
        requireNonNull(DataContext.Variable.TIME_FRAME_SET.get(root));
    final TimeFrame timeFrame = timeFrameSet.get(timeFrameName);
    return timeFrameSet.floorDate(date, timeFrame);
  }

  /** SQL {@code CEIL} function applied to a {@code DATE} value
   * and a custom time frame.
   *
   * <p>Custom time frames are created and accessed as described in
   * {@link #customDateAdd}. */
  public static int customDateCeil(DataContext root,
      String timeFrameName, int date) {
    final TimeFrameSet timeFrameSet =
        requireNonNull(DataContext.Variable.TIME_FRAME_SET.get(root));
    final TimeFrame timeFrame = timeFrameSet.get(timeFrameName);
    return timeFrameSet.ceilDate(date, timeFrame);
  }

  /** SQL {@code FLOOR} function applied to a {@code TIMESTAMP} value
   * and a custom time frame.
   *
   * <p>Custom time frames are created and accessed as described in
   * {@link #customDateAdd}. */
  public static long customTimestampFloor(DataContext root,
      String timeFrameName, long timestamp) {
    final TimeFrameSet timeFrameSet =
        requireNonNull(DataContext.Variable.TIME_FRAME_SET.get(root));
    final TimeFrame timeFrame = timeFrameSet.get(timeFrameName);
    return timeFrameSet.floorTimestamp(timestamp, timeFrame);
  }

  /** SQL {@code CEIL} function applied to a {@code TIMESTAMP} value
   * and a custom time frame.
   *
   * <p>Custom time frames are created and accessed as described in
   * {@link #customDateAdd}. */
  public static long customTimestampCeil(DataContext root,
      String timeFrameName, long timestamp) {
    final TimeFrameSet timeFrameSet =
        requireNonNull(DataContext.Variable.TIME_FRAME_SET.get(root));
    final TimeFrame timeFrame = timeFrameSet.get(timeFrameName);
    return timeFrameSet.ceilTimestamp(timestamp, timeFrame);
  }

  /** SQL {@code TRANSLATE(string, search_chars, replacement_chars)}
   * function. */
  public static String translate3(String s, String search, String replacement) {
    return org.apache.commons.lang3.StringUtils.replaceChars(s, search, replacement);
  }

  /** SQL {@code REPLACE(string, search, replacement)} function. */
  public static String replace(String s, String search, String replacement) {
    return s.replace(search, replacement);
  }

  /** Helper for "array element reference". Caller has already ensured that
   * array and index are not null.
   *
   * <p>Index may be 0- or 1-based depending on which array subscript operator
   * is being used. {@code ITEM}, {@code ORDINAL}, and {@code SAFE_ORDINAL}
   * are 1-based, while {@code OFFSET} and {@code SAFE_OFFSET} are 0-based.
   *
   * <p>The {@code ITEM}, {@code SAFE_OFFSET}, and {@code SAFE_ORDINAL}
   * operators return null if the index is out of bounds, while the others
   * throw an error. */
  public static @Nullable Object arrayItem(List list, int item, int offset,
      boolean safe) {
    if (item < offset || item > list.size() + 1 - offset) {
      if (safe) {
        return null;
      } else {
        throw RESOURCE.arrayIndexOutOfBounds(item).ex();
      }
    }
    return list.get(item - offset);
  }

  /** Helper for "map element reference". Caller has already ensured that
   * array and index are not null. Index is 1-based, per SQL. */
  public static @Nullable Object mapItem(Map map, Object item) {
    return map.get(item);
  }

  /** Implements the {@code [ ... ]} operator on an object whose type is not
   * known until runtime.
   */
  public static @Nullable Object item(Object object, Object index) {
    if (object instanceof Map) {
      return mapItem((Map) object, index);
    }
    if (object instanceof List && index instanceof Number) {
      return arrayItem((List) object, ((Number) index).intValue(), 1, true);
    }
    if (index instanceof Number) {
      return structAccess(object, ((Number) index).intValue() - 1, null); // 1 indexed
    }
    if (index instanceof String) {
      return structAccess(object, -1, index.toString());
    }

    return null;
  }

  /** As {@link #arrayItem} method, but allows array to be nullable. */
  public static @Nullable Object arrayItemOptional(@Nullable List list,
      int item, int offset, boolean safe) {
    if (list == null) {
      return null;
    }
    return arrayItem(list, item, offset, safe);
  }

  /** As {@link #mapItem} method, but allows map to be nullable. */
  public static @Nullable Object mapItemOptional(@Nullable Map map,
      Object item) {
    if (map == null) {
      return null;
    }
    return mapItem(map, item);
  }

  /** As {@link #item} method, but allows object to be nullable. */
  public static @Nullable Object itemOptional(@Nullable Object object,
      Object index) {
    if (object == null) {
      return null;
    }
    return item(object, index);
  }


  /** NULL &rarr; FALSE, FALSE &rarr; FALSE, TRUE &rarr; TRUE. */
  public static boolean isTrue(@Nullable Boolean b) {
    return b != null && b;
  }

  /** NULL &rarr; FALSE, FALSE &rarr; TRUE, TRUE &rarr; FALSE. */
  public static boolean isFalse(@Nullable Boolean b) {
    return b != null && !b;
  }

  /** NULL &rarr; TRUE, FALSE &rarr; TRUE, TRUE &rarr; FALSE. */
  public static boolean isNotTrue(@Nullable Boolean b) {
    return b == null || !b;
  }

  /** NULL &rarr; TRUE, FALSE &rarr; FALSE, TRUE &rarr; TRUE. */
  public static boolean isNotFalse(@Nullable Boolean b) {
    return b == null || b;
  }

  /** NULL &rarr; NULL, FALSE &rarr; TRUE, TRUE &rarr; FALSE. */
  public static @PolyNull Boolean not(@PolyNull Boolean b) {
    return b == null ? castNonNull(null) : !b;
  }

  /** Converts a JDBC array to a list. */
  public static @PolyNull List arrayToList(final java.sql.@PolyNull Array a) {
    if (a == null) {
      return castNonNull(null);
    }
    try {
      return Primitive.asList(a.getArray());
    } catch (SQLException e) {
      throw Util.toUnchecked(e);
    }
  }

  /** Support the {@code CURRENT VALUE OF sequence} operator. */
  @NonDeterministic
  public static long sequenceCurrentValue(String key) {
    return getAtomicLong(key).get();
  }

  /** Support the {@code NEXT VALUE OF sequence} operator. */
  @NonDeterministic
  public static long sequenceNextValue(String key) {
    return getAtomicLong(key).incrementAndGet();
  }

  private static AtomicLong getAtomicLong(String key) {
    final Map<String, AtomicLong> map =
        requireNonNull(THREAD_SEQUENCES.get(), "THREAD_SEQUENCES.get()");
    AtomicLong atomic = map.get(key);
    if (atomic == null) {
      atomic = new AtomicLong();
      map.put(key, atomic);
    }
    return atomic;
  }

  /** Support the ARRAYS_OVERLAP function. */
  public static @Nullable Boolean arraysOverlap(List list1, List list2) {
    if (list1.size() > list2.size()) {
      return arraysOverlap(list2, list1);
    }
    final List smaller = list1;
    final List bigger = list2;
    boolean hasNull = false;
    if (smaller.size() > 0 && bigger.size() > 0) {
      final Set smallestSet = new HashSet(smaller);
      hasNull = smallestSet.remove(null);
      for (Object element : bigger) {
        if (element == null) {
          hasNull = true;
        } else if (smallestSet.contains(element)) {
          return true;
        }
      }
    }
    if (hasNull) {
      return null;
    } else {
      return false;
    }
  }

  /** Support the ARRAYS_ZIP function. */
  @SuppressWarnings("argument.type.incompatible")
  public static List arraysZip(List... lists) {
    final int biggestCardinality = lists.length == 0
        ? 0
        : Arrays.stream(lists).mapToInt(List::size).max().getAsInt();

    final List result = new ArrayList(biggestCardinality);
    for (int i = 0; i < biggestCardinality; i++) {
      List<Object> row = new ArrayList<>();
      Object value;
      for (List list : lists) {
        if (i < list.size() && list.get(i) != null) {
          value = list.get(i);
        } else {
          value = null;
        }
        row.add(value);
      }
      result.add(row);
    }
    return result;
  }

  /** Support the ARRAY_COMPACT function. */
  public static List compact(List list) {
    final List result = new ArrayList();
    for (Object element : list) {
      if (element != null) {
        result.add(element);
      }
    }
    return result;
  }

  /** Support the ARRAY_APPEND function. */
  public static List arrayAppend(List list, Object element) {
    final List result = new ArrayList(list.size() + 1);
    result.addAll(list);
    result.add(element);
    return result;
  }

  /** Support the ARRAY_DISTINCT function.
   *
   * <p>Note: If the list does not contain null,
   * {@link Util#distinctList(List)} is probably faster. */
  public static List distinct(List list) {
    Set result = new LinkedHashSet<>(list);
    return new ArrayList<>(result);
  }

  /** Support the ARRAY_MAX function. */
  public static @Nullable <T extends Object & Comparable<? super T>> T arrayMax(
      List<? extends T> list) {

    T max = null;
    for (int i = 0; i < list.size(); i++) {
      T item = list.get(i);
      if (item != null && (max == null || item.compareTo(max) > 0)) {
        max = item;
      }
    }
    return max;
  }

  /** Support the ARRAY_MIN function. */
  public static @Nullable <T extends Object & Comparable<? super T>> T arrayMin(
      List<? extends T> list) {

    T min = null;
    for (int i = 0; i < list.size(); i++) {
      T item = list.get(i);
      if (item != null && (min == null || item.compareTo(min) < 0)) {
        min = item;
      }
    }
    return min;
  }

  /** Support the ARRAY_PREPEND function. */
  public static List arrayPrepend(List list, Object element) {
    final List result = new ArrayList(list.size() + 1);
    result.add(element);
    result.addAll(list);
    return result;
  }

  /** Support the ARRAY_POSITION function. */
  public static Long arrayPosition(List list, Object element) {
    final int index = list.indexOf(element);
    if (index != -1) {
      return Long.valueOf(index + 1L);
    }
    return 0L;
  }

  /** Support the ARRAY_REMOVE function. */
  public static List arrayRemove(List list, Object element) {
    final List result = new ArrayList();
    for (Object obj : list) {
      if (obj == null || !obj.equals(element)) {
        result.add(obj);
      }
    }
    return result;
  }

  /** Support the ARRAY_REPEAT function. */
  public static @Nullable List<Object> repeat(Object element, Object count) {
    if (count == null) {
      return null;
    }
    int numberOfElement = (int) count;
    if (numberOfElement < 0) {
      numberOfElement = 0;
    }
    return Collections.nCopies(numberOfElement, element);
  }

  /** Support the ARRAY_EXCEPT function. */
  public static List arrayExcept(List list1, List list2) {
    final Set result = new LinkedHashSet<>(list1);
    result.removeAll(list2);
    return new ArrayList<>(result);
  }

  /** Support the ARRAY_INSERT function. */
  public static @Nullable List arrayInsert(List baselist, Object pos, Object val) {
    if (baselist == null || pos == null) {
      return null;
    }
    int posInt = (int) pos;
    Object[] baseArray = baselist.toArray();
    if (posInt == 0 || posInt >= MAX_ARRAY_LENGTH || posInt <= -MAX_ARRAY_LENGTH) {
      throw new IllegalArgumentException("The index 0 is invalid. "
          + "An index shall be either < 0 or > 0 (the first element has index 1) "
          + "and not exceeds the allowed limit.");
    }

    boolean usePositivePos = posInt > 0;

    if (usePositivePos) {
      int newArrayLength = Math.max(baseArray.length + 1, posInt);

      if (newArrayLength > MAX_ARRAY_LENGTH) {
        throw new IndexOutOfBoundsException(
            String.format(Locale.ROOT, "The new array length %s exceeds the allowed limit.",
                newArrayLength));
      }

      Object[] newArray = new Object[newArrayLength];

      int posIndex = posInt - 1;
      if (posIndex < baseArray.length) {
        System.arraycopy(baseArray, 0, newArray, 0, posIndex);
        newArray[posIndex] = val;
        System.arraycopy(baseArray, posIndex, newArray, posIndex + 1, baseArray.length - posIndex);
      } else {
        System.arraycopy(baseArray, 0, newArray, 0, baseArray.length);
        newArray[posIndex] = val;
      }

      return Arrays.asList(newArray);
    } else {
      int posIndex = posInt;

      boolean newPosExtendsArrayLeft = baseArray.length + posIndex < 0;

      if (newPosExtendsArrayLeft) {
        // special case, if the new position is negative but larger than the current array size
        // place the new item at start of array, place the current array contents at the end
        // and fill the newly created array elements in middle with a null
        int newArrayLength = -posIndex + 1;

        if (newArrayLength > MAX_ARRAY_LENGTH) {
          throw new IndexOutOfBoundsException(
              String.format(Locale.ROOT, "The new array length %s exceeds the allowed limit.",
                  newArrayLength));
        }

        Object[] newArray = new Object[newArrayLength];
        System.arraycopy(baseArray, 0, newArray, Math.abs(posIndex + baseArray.length) + 1,
            baseArray.length);
        newArray[0] = val;

        return Arrays.asList(newArray);
      } else {
        posIndex = posIndex + baseArray.length;

        int newArrayLength = Math.max(baseArray.length + 1, posIndex + 1);

        if (newArrayLength > MAX_ARRAY_LENGTH) {
          throw new IndexOutOfBoundsException(
              String.format(Locale.ROOT, "The new array length %s exceeds the allowed limit.",
                  newArrayLength));
        }

        Object[] newArray = new Object[newArrayLength];

        if (posIndex < baseArray.length) {
          System.arraycopy(baseArray, 0, newArray, 0, posIndex);
          newArray[posIndex] = val;
          System.arraycopy(baseArray, posIndex, newArray, posIndex + 1,
              baseArray.length - posIndex);
        } else {
          System.arraycopy(baseArray, 0, newArray, 0, baseArray.length);
          newArray[posIndex] = val;
        }

        return Arrays.asList(newArray);
      }
    }
  }

  /** Support the ARRAY_INTERSECT function. */
  public static List arrayIntersect(List list1, List list2) {
    final Set result = new LinkedHashSet<>(list1);
    result.retainAll(list2);
    return new ArrayList<>(result);
  }

  /** Support the ARRAY_UNION function. */
  public static List arrayUnion(List list1, List list2) {
    final Set result = new LinkedHashSet<>();
    result.addAll(list1);
    result.addAll(list2);
    return new ArrayList<>(result);
  }

  /** Support the SORT_ARRAY function. */
  public static List sortArray(List list, boolean ascending) {
    Comparator comparator = ascending
        ? Comparator.nullsFirst(Comparator.naturalOrder())
        : Comparator.nullsLast(Comparator.reverseOrder());
    list.sort(comparator);
    return list;
  }

  /** Support the MAP_CONCAT function. */
  public static Map mapConcat(Map... maps) {
    final Map result = new LinkedHashMap();
    Arrays.stream(maps).forEach(result::putAll);
    return result;
  }

  /** Support the MAP_ENTRIES function. */
  public static List mapEntries(Map<Object, Object> map) {
    final List result = new ArrayList(map.size());
    for (Map.Entry<Object, Object> entry : map.entrySet()) {
      result.add(Arrays.asList(entry.getKey(), entry.getValue()));
    }
    return result;
  }

  /** Support the MAP_KEYS function. */
  public static List mapKeys(Map map) {
    return new ArrayList<>(map.keySet());
  }

  /** Support the MAP_VALUES function. */
  public static List mapValues(Map map) {
    return new ArrayList<>(map.values());
  }

  /** Support the MAP_FROM_ARRAYS function. */
  public static Map mapFromArrays(List keysArray, List valuesArray) {
    if (keysArray.size() != valuesArray.size()) {
      throw RESOURCE.illegalArgumentsInMapFromArraysFunc(keysArray.size(), valuesArray.size()).ex();
    }
    final Map map = new LinkedHashMap<>();
    for (int i = 0; i < keysArray.size(); i++) {
      map.put(keysArray.get(i), valuesArray.get(i));
    }
    return map;
  }

  /** Support the MAP_FROM_ENTRIES function. */
  public static @Nullable Map mapFromEntries(List entries) {
    final Map map = new LinkedHashMap<>();
    for (Object entry: entries) {
      if (entry == null) {
        return null;
      }
      map.put(structAccess(entry, 0, null), structAccess(entry, 1, null));
    }
    return map;
  }

  /** Support the STR_TO_MAP function. */
  public static Map strToMap(String string, String stringDelimiter, String keyValueDelimiter) {
    final Map map = new LinkedHashMap();
    final String[] keyValues = string.split(stringDelimiter, -1);
    for (String s : keyValues) {
      String[] keyValueArray = s.split(keyValueDelimiter, 2);
      String key = keyValueArray[0];
      String value = keyValueArray.length < 2
          ? null
          : keyValueArray[1];
      map.put(key, value);
    }
    return map;
  }

  /** Support the SLICE function. */
  public static List slice(List list) {
    List result = new ArrayList(list.size());
    for (Object e : list) {
      result.add(structAccess(e, 0, null));
    }
    return result;
  }

  /** Support the ELEMENT function. */
  public static @Nullable Object element(List list) {
    switch (list.size()) {
    case 0:
      return null;
    case 1:
      return list.get(0);
    default:
      throw RESOURCE.moreThanOneValueInList(list.toString()).ex();
    }
  }

  /** Support the MEMBER OF function. */
  public static boolean memberOf(@Nullable Object object, Collection collection) {
    return collection.contains(object);
  }

  /** Support the MULTISET INTERSECT DISTINCT function. */
  public static <E> Collection<E> multisetIntersectDistinct(Collection<E> c1,
      Collection<E> c2) {
    final Set<E> result = new HashSet<>(c1);
    result.retainAll(c2);
    return new ArrayList<>(result);
  }

  /** Support the MULTISET INTERSECT ALL function. */
  public static <E> Collection<E> multisetIntersectAll(Collection<E> c1,
      Collection<E> c2) {
    final List<E> result = new ArrayList<>(c1.size());
    final List<E> c2Copy = new ArrayList<>(c2);
    for (E e : c1) {
      if (c2Copy.remove(e)) {
        result.add(e);
      }
    }
    return result;
  }

  /** Support the MULTISET EXCEPT ALL function. */
  @SuppressWarnings("JdkObsolete")
  public static <E> Collection<E> multisetExceptAll(Collection<E> c1,
      Collection<E> c2) {
    // TOOD: use Multisets?
    final List<E> result = new LinkedList<>(c1);
    for (E e : c2) {
      result.remove(e);
    }
    return result;
  }

  /** Support the MULTISET EXCEPT DISTINCT function. */
  public static <E> Collection<E> multisetExceptDistinct(Collection<E> c1,
      Collection<E> c2) {
    final Set<E> result = new HashSet<>(c1);
    result.removeAll(c2);
    return new ArrayList<>(result);
  }

  /** Support the IS A SET function. */
  public static boolean isASet(Collection collection) {
    if (collection instanceof Set) {
      return true;
    }
    // capacity calculation is in the same way like for new HashSet(Collection)
    // however return immediately in case of duplicates
    Set set = new HashSet(Math.max((int) (collection.size() / .75f) + 1, 16));
    for (Object e : collection) {
      if (!set.add(e)) {
        return false;
      }
    }
    return true;
  }

  /** Support the SUBMULTISET OF function. */
  @SuppressWarnings("JdkObsolete")
  public static boolean submultisetOf(Collection possibleSubMultiset,
      Collection multiset) {
    if (possibleSubMultiset.size() > multiset.size()) {
      return false;
    }
    // TODO: use Multisets?
    Collection multisetLocal = new LinkedList(multiset);
    for (Object e : possibleSubMultiset) {
      if (!multisetLocal.remove(e)) {
        return false;
      }
    }
    return true;
  }

  /** Support the MULTISET UNION function. */
  public static Collection multisetUnionDistinct(Collection collection1,
      Collection collection2) {
    // capacity calculation is in the same way like for new HashSet(Collection)
    Set resultCollection =
        new HashSet(Math.max((int) ((collection1.size() + collection2.size()) / .75f) + 1, 16));
    resultCollection.addAll(collection1);
    resultCollection.addAll(collection2);
    return new ArrayList(resultCollection);
  }

  /** Support the MULTISET UNION ALL function. */
  public static Collection multisetUnionAll(Collection collection1,
      Collection collection2) {
    List resultCollection = new ArrayList(collection1.size() + collection2.size());
    resultCollection.addAll(collection1);
    resultCollection.addAll(collection2);
    return resultCollection;
  }

  /** Support the ARRAY_REVERSE function. */
  public static List reverse(List list) {
    Collections.reverse(list);
    return list;
  }

  /** SQL {@code ARRAY_TO_STRING(array, delimiter)} function. */
  public static String arrayToString(List list, String delimiter) {
    return arrayToString(list, delimiter, null);
  }

  /** SQL {@code ARRAY_TO_STRING(array, delimiter, nullText)} function. */
  public static String arrayToString(List list, String delimiter, @Nullable String nullText) {
    StringBuilder sb = new StringBuilder();
    boolean isFirst = true;
    for (Object item : list) {
      String str;
      if (item == null) {
        if (nullText == null) {
          continue;
        } else {
          str = nullText;
        }
      } else if (item instanceof String) {
        str = (String) item;
      } else if (item instanceof ByteString) {
        str = item.toString();
      } else {
        throw new IllegalStateException(
            "arrayToString supports only String or ByteString, but got "
                + item.getClass().getName());
      }

      if (!isFirst) {
        sb.append(delimiter);
      }
      sb.append(str);
      isFirst = false;
    }
    return sb.toString();
  }

  /**
   * Function that, given a certain List containing single-item structs (i.e. arrays / lists with
   * a single item), builds an Enumerable that returns those single items inside the structs.
   */
  public static Function1<List<Object>, Enumerable<Object>> flatList() {
    return inputList -> Linq4j.asEnumerable(inputList).select(v -> structAccess(v, 0, null));
  }

  public static Function1<Object, Enumerable<ComparableList<Comparable>>> flatProduct(
      final int[] fieldCounts, final boolean withOrdinality,
      final FlatProductInputType[] inputTypes) {
    if (fieldCounts.length == 1) {
      if (!withOrdinality && inputTypes[0] == FlatProductInputType.SCALAR) {
        //noinspection unchecked
        return (Function1) LIST_AS_ENUMERABLE;
      } else {
        return row -> p2(new Object[] { row }, fieldCounts, withOrdinality,
            inputTypes);
      }
    }
    return lists -> p2((Object[]) lists, fieldCounts, withOrdinality,
        inputTypes);
  }

  private static Enumerable<FlatLists.ComparableList<Comparable>> p2(
      Object[] lists, int[] fieldCounts, boolean withOrdinality,
      FlatProductInputType[] inputTypes) {
    final List<Enumerator<List<Comparable>>> enumerators = new ArrayList<>();
    int totalFieldCount = 0;
    for (int i = 0; i < lists.length; i++) {
      int fieldCount = fieldCounts[i];
      FlatProductInputType inputType = inputTypes[i];
      Object inputObject = lists[i];
      switch (inputType) {
      case SCALAR:
        @SuppressWarnings("unchecked") List<Comparable> list =
            (List<Comparable>) inputObject;
        enumerators.add(
            Linq4j.transform(
                Linq4j.enumerator(list), FlatLists::of));
        break;
      case LIST:
        @SuppressWarnings("unchecked") List<List<Comparable>> listList =
            (List<List<Comparable>>) inputObject;
        enumerators.add(Linq4j.enumerator(listList));
        break;
      case MAP:
        @SuppressWarnings("unchecked") Map<Comparable, Comparable> map =
            (Map<Comparable, Comparable>) inputObject;
        Enumerator<Map.Entry<Comparable, Comparable>> enumerator =
            Linq4j.enumerator(map.entrySet());

        Enumerator<List<Comparable>> transformed =
            Linq4j.transform(enumerator,
                e -> FlatLists.of(e.getKey(), e.getValue()));
        enumerators.add(transformed);
        break;
      default:
        break;
      }
      if (fieldCount < 0) {
        ++totalFieldCount;
      } else {
        totalFieldCount += fieldCount;
      }
    }
    if (withOrdinality) {
      ++totalFieldCount;
    }
    return product(enumerators, totalFieldCount, withOrdinality);
  }

  public static Object[] array(Object... args) {
    return args;
  }

  /**
   * Returns whether there is an element in {@code list} for which {@code predicate} is true.
   * Also, if {@code predicate} returns null for any element of {@code list}
   * and does not return {@code true} for any element of {@code list},
   * the result will be {@code null}, not {@code false}.
   */
  public static @Nullable <E> Boolean nullableExists(List<? extends E> list,
      Function1<E, Boolean> predicate) {
    boolean nullExists = false;
    for (E e : list) {
      Boolean res = predicate.apply(e);
      if (res == null) {
        nullExists = true;
      } else if (res) {
        return true;
      }
    }
    return nullExists ? null : false;
  }

  /**
   * Returns whether {@code predicate} is true for all elements of {@code list}.
   * Also, if {@code predicate} returns null for any element of {@code list}
   * and does not return {@code false} for any element,
   * the result will be {@code null}, not {@code true}.
   */
  public static @Nullable <E> Boolean nullableAll(List<? extends E> list,
      Function1<E, Boolean> predicate) {
    boolean nullExists = false;
    for (E e : list) {
      Boolean res = predicate.apply(e);
      if (res == null) {
        nullExists = true;
      } else if (!res) {
        return false;
      }
    }
    return nullExists ? null : true;
  }

  /** Similar to {@link Linq4j#product(Iterable)} but each resulting list
   * implements {@link FlatLists.ComparableList}. */
  public static <E extends Comparable> Enumerable<FlatLists.ComparableList<E>> product(
      final List<Enumerator<List<E>>> enumerators, final int fieldCount,
      final boolean withOrdinality) {
    return new AbstractEnumerable<FlatLists.ComparableList<E>>() {
      @Override public Enumerator<FlatLists.ComparableList<E>> enumerator() {
        return new ProductComparableListEnumerator<>(enumerators, fieldCount,
            withOrdinality);
      }
    };
  }

  /**
   * Implements the {@code .} (field access) operator on an object
   * whose type is not known until runtime.
   *
   * <p>A struct object can be represented in various ways by the
   * runtime and depends on the
   * {@link org.apache.calcite.adapter.enumerable.JavaRowFormat}.
   */
  @Experimental
  public static @Nullable Object structAccess(@Nullable Object structObject, int index,
      @Nullable String fieldName) {
    if (structObject == null) {
      return null;
    }

    if (structObject instanceof Object[]) {
      return ((Object[]) structObject)[index];
    } else if (structObject instanceof List) {
      return ((List) structObject).get(index);
    } else if (structObject instanceof Row) {
      return ((Row) structObject).getObject(index);
    } else {
      Class<?> beanClass = structObject.getClass();
      try {
        if (fieldName == null) {
          throw new IllegalStateException("Field name cannot be null for struct field access");
        }
        Field structField = beanClass.getDeclaredField(fieldName);
        return structField.get(structObject);
      } catch (NoSuchFieldException | IllegalAccessException ex) {
        throw RESOURCE.failedToAccessField(fieldName, index, beanClass.getName()).ex(ex);
      }
    }
  }

  /** Enumerates over the cartesian product of the given lists, returning
   * a comparable list for each row.
   *
   * @param <E> element type */
  private static class ProductComparableListEnumerator<E extends Comparable>
      extends CartesianProductEnumerator<List<E>, FlatLists.ComparableList<E>> {
    final Object[] flatElements;
    final List<Object> list;
    private final boolean withOrdinality;
    private int ordinality;

    ProductComparableListEnumerator(List<Enumerator<List<E>>> enumerators,
        int fieldCount, boolean withOrdinality) {
      super(enumerators);
      this.withOrdinality = withOrdinality;
      flatElements = new Object[fieldCount];
      list = Arrays.asList(flatElements);
    }

    @Override public boolean moveNext() {
      boolean hasNext = super.moveNext();
      if (hasNext && withOrdinality) {
        ordinality++;
      }
      return hasNext;
    }

    @Override public FlatLists.ComparableList<E> current() {
      int i = 0;
      for (Object element : (Object[]) elements) {
        Object[] a;
        if (element.getClass().isArray()) {
          a = (Object[]) element;
        } else {
          final List list2 = (List) element;
          a = list2.toArray();
        }
        System.arraycopy(a, 0, flatElements, i, a.length);
        i += a.length;
      }
      if (withOrdinality) {
        flatElements[i] = ordinality;
      }
      //noinspection unchecked
      return (FlatLists.ComparableList) FlatLists.of(list);
    }

    @Override public void reset() {
      super.reset();
      if (withOrdinality) {
        ordinality = 0;
      }
    }
  }

  /** Specifies scope to search for {@code #containsSubstr}.  */
  public enum JsonScope {
    JSON_KEYS, JSON_KEYS_AND_VALUES, JSON_VALUES
  }

  /** Type of argument passed into {@link #flatProduct}. */
  public enum FlatProductInputType {
    SCALAR, LIST, MAP
  }

  /** Type of part to extract passed into {@link ParseUrlFunction#parseUrl}. */
  private enum PartToExtract {
    HOST,
    PATH,
    QUERY,
    REF,
    PROTOCOL,
    FILE,
    AUTHORITY,
    USERINFO;
  }
}
