/*
 * 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.cassandra.db.partitions;

import java.io.EOFException;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

import com.google.common.annotations.VisibleForTesting;
import com.google.common.collect.Iterables;
import com.google.common.collect.Lists;
import com.google.common.primitives.Ints;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import org.apache.cassandra.db.*;
import org.apache.cassandra.db.filter.ColumnFilter;
import org.apache.cassandra.db.rows.*;
import org.apache.cassandra.index.IndexRegistry;
import org.apache.cassandra.io.util.DataInputBuffer;
import org.apache.cassandra.io.util.DataInputPlus;
import org.apache.cassandra.io.util.DataOutputBuffer;
import org.apache.cassandra.io.util.DataOutputPlus;
import org.apache.cassandra.schema.ColumnMetadata;
import org.apache.cassandra.schema.Schema;
import org.apache.cassandra.schema.TableId;
import org.apache.cassandra.schema.TableMetadata;
import org.apache.cassandra.utils.btree.BTree;
import org.apache.cassandra.utils.btree.UpdateFunction;
import org.apache.cassandra.utils.vint.VIntCoding;

import static org.apache.cassandra.db.rows.UnfilteredRowIteratorSerializer.IS_EMPTY;

/**
 * Stores updates made on a partition.
 * <p>
 * A PartitionUpdate object requires that all writes/additions are performed before we
 * try to read the updates (attempts to write to the PartitionUpdate after a read method
 * has been called will result in an exception being thrown). In other words, a Partition
 * is mutable while it's written but becomes immutable as soon as it is read.
 * <p>
 * A typical usage is to create a new update ({@code new PartitionUpdate(metadata, key, columns, capacity)})
 * and then add rows and range tombstones through the {@code add()} methods (the partition
 * level deletion time can also be set with {@code addPartitionDeletion()}). However, there
 * is also a few static helper constructor methods for special cases ({@code emptyUpdate()},
 * {@code fullPartitionDelete} and {@code singleRowUpdate}).
 */
public class PartitionUpdate extends AbstractBTreePartition
{
    protected static final Logger logger = LoggerFactory.getLogger(PartitionUpdate.class);

    public static final PartitionUpdateSerializer serializer = new PartitionUpdateSerializer();

    private final BTreePartitionData holder;
    private final DeletionInfo deletionInfo;
    private final TableMetadata metadata;

    private final boolean canHaveShadowedData;

    private PartitionUpdate(TableMetadata metadata,
                            DecoratedKey key,
                            BTreePartitionData holder,
                            MutableDeletionInfo deletionInfo,
                            boolean canHaveShadowedData)
    {
        super(key);
        this.metadata = metadata;
        this.holder = holder;
        this.deletionInfo = deletionInfo;
        this.canHaveShadowedData = canHaveShadowedData;
    }

    /**
     * Creates a empty immutable partition update.
     *
     * @param metadata the metadata for the created update.
     * @param key the partition key for the created update.
     *
     * @return the newly created empty (and immutable) update.
     */
    public static PartitionUpdate emptyUpdate(TableMetadata metadata, DecoratedKey key)
    {
        MutableDeletionInfo deletionInfo = MutableDeletionInfo.live();
        BTreePartitionData holder = new BTreePartitionData(RegularAndStaticColumns.NONE, BTree.empty(), deletionInfo, Rows.EMPTY_STATIC_ROW, EncodingStats.NO_STATS);
        return new PartitionUpdate(metadata, key, holder, deletionInfo, false);
    }

    /**
     * Creates an immutable partition update that entirely deletes a given partition.
     *
     * @param metadata the metadata for the created update.
     * @param key the partition key for the partition that the created update should delete.
     * @param timestamp the timestamp for the deletion.
     * @param nowInSec the current time in seconds to use as local deletion time for the partition deletion.
     *
     * @return the newly created partition deletion update.
     */
    public static PartitionUpdate fullPartitionDelete(TableMetadata metadata, DecoratedKey key, long timestamp, long nowInSec)
    {
        MutableDeletionInfo deletionInfo = new MutableDeletionInfo(timestamp, nowInSec);
        BTreePartitionData holder = new BTreePartitionData(RegularAndStaticColumns.NONE, BTree.empty(), deletionInfo, Rows.EMPTY_STATIC_ROW, EncodingStats.NO_STATS);
        return new PartitionUpdate(metadata, key, holder, deletionInfo, false);
    }

    /**
     * Creates an immutable partition update that contains a single row update.
     *
     * @param metadata the metadata for the created update.
     * @param key the partition key for the partition to update.
     * @param row the row for the update (may be null).
     * @param row the static row for the update (may be null).
     *
     * @return the newly created partition update containing only {@code row}.
     */
    public static PartitionUpdate singleRowUpdate(TableMetadata metadata, DecoratedKey key, Row row, Row staticRow)
    {
        MutableDeletionInfo deletionInfo = MutableDeletionInfo.live();
        BTreePartitionData holder = new BTreePartitionData(
            new RegularAndStaticColumns(
                staticRow == null ? Columns.NONE : Columns.from(staticRow),
                row == null ? Columns.NONE : Columns.from(row)
            ),
            row == null ? BTree.empty() : BTree.singleton(row),
            deletionInfo,
            staticRow == null ? Rows.EMPTY_STATIC_ROW : staticRow,
            EncodingStats.NO_STATS
        );
        return new PartitionUpdate(metadata, key, holder, deletionInfo, false);
    }

    /**
     * Creates an immutable partition update that contains a single row update.
     *
     * @param metadata the metadata for the created update.
     * @param key the partition key for the partition to update.
     * @param row the row for the update (may be static).
     *
     * @return the newly created partition update containing only {@code row}.
     */
    public static PartitionUpdate singleRowUpdate(TableMetadata metadata, DecoratedKey key, Row row)
    {
        return singleRowUpdate(metadata, key, row.isStatic() ? null : row, row.isStatic() ? row : null);
    }

    /**
     * Creates an immutable partition update that contains a single row update.
     *
     * @param metadata the metadata for the created update.
     * @param key the partition key for the partition to update.
     * @param row the row for the update.
     *
     * @return the newly created partition update containing only {@code row}.
     */
    public static PartitionUpdate singleRowUpdate(TableMetadata metadata, ByteBuffer key, Row row)
    {
        return singleRowUpdate(metadata, metadata.partitioner.decorateKey(key), row);
    }

    /**
     * Turns the given iterator into an update.
     *
     * @param iterator the iterator to turn into updates.
     * @param filter the column filter used when querying {@code iterator}. This is used to make
     * sure we don't include data for which the value has been skipped while reading (as we would
     * then be writing something incorrect).
     *
     * Warning: this method does not close the provided iterator, it is up to
     * the caller to close it.
     */
    @SuppressWarnings("resource")
    public static PartitionUpdate fromIterator(UnfilteredRowIterator iterator, ColumnFilter filter)
    {
        iterator = UnfilteredRowIterators.withOnlyQueriedData(iterator, filter);
        BTreePartitionData holder = build(iterator, 16);
        MutableDeletionInfo deletionInfo = (MutableDeletionInfo) holder.deletionInfo;
        return new PartitionUpdate(iterator.metadata(), iterator.partitionKey(), holder, deletionInfo, false);
    }

    /**
     * Turns the given iterator into an update.
     *
     * @param iterator the iterator to turn into updates.
     * @param filter the column filter used when querying {@code iterator}. This is used to make
     * sure we don't include data for which the value has been skipped while reading (as we would
     * then be writing something incorrect).
     *
     * Warning: this method does not close the provided iterator, it is up to
     * the caller to close it.
     */
    @SuppressWarnings("resource")
    public static PartitionUpdate fromIterator(RowIterator iterator, ColumnFilter filter)
    {
        iterator = RowIterators.withOnlyQueriedData(iterator, filter);
        MutableDeletionInfo deletionInfo = MutableDeletionInfo.live();
        BTreePartitionData holder = build(iterator, deletionInfo, true);
        return new PartitionUpdate(iterator.metadata(), iterator.partitionKey(), holder, deletionInfo, false);
    }


    public PartitionUpdate withOnlyPresentColumns()
    {
        Set<ColumnMetadata> columnSet = new HashSet<>();

        for (Row row : this)
            for (ColumnData column : row)
                columnSet.add(column.column());

        RegularAndStaticColumns columns = RegularAndStaticColumns.builder().addAll(columnSet).build();
        return new PartitionUpdate(this.metadata, this.partitionKey, this.holder.withColumns(columns), this.deletionInfo.mutableCopy(), false);
    }


    protected boolean canHaveShadowedData()
    {
        return canHaveShadowedData;
    }

    /**
     * Deserialize a partition update from a provided byte buffer.
     *
     * @param bytes the byte buffer that contains the serialized update.
     * @param version the version with which the update is serialized.
     *
     * @return the deserialized update or {@code null} if {@code bytes == null}.
     */
    @SuppressWarnings("resource")
    public static PartitionUpdate fromBytes(ByteBuffer bytes, int version)
    {
        if (bytes == null)
            return null;

        try
        {
            return serializer.deserialize(new DataInputBuffer(bytes, true),
                                          version,
                                          DeserializationHelper.Flag.LOCAL);
        }
        catch (IOException e)
        {
            throw new RuntimeException(e);
        }
    }

    /**
     * Serialize a partition update as a byte buffer.
     *
     * @param update the partition update to serialize.
     * @param version the version to serialize the update into.
     *
     * @return a newly allocated byte buffer containing the serialized update.
     */
    public static ByteBuffer toBytes(PartitionUpdate update, int version)
    {
        try (DataOutputBuffer out = new DataOutputBuffer())
        {
            serializer.serialize(update, out, version);
            return out.buffer();
        }
        catch (IOException e)
        {
            throw new RuntimeException(e);
        }
    }

    /**
     * Creates a partition update that entirely deletes a given partition.
     *
     * @param metadata the metadata for the created update.
     * @param key the partition key for the partition that the created update should delete.
     * @param timestamp the timestamp for the deletion.
     * @param nowInSec the current time in seconds to use as local deletion time for the partition deletion.
     *
     * @return the newly created partition deletion update.
     */
    public static PartitionUpdate fullPartitionDelete(TableMetadata metadata, ByteBuffer key, long timestamp, long nowInSec)
    {
        return fullPartitionDelete(metadata, metadata.partitioner.decorateKey(key), timestamp, nowInSec);
    }

    /**
     * Merges the provided updates, yielding a new update that incorporates all those updates.
     *
     * @param updates the collection of updates to merge. This shouldn't be empty.
     *
     * @return a partition update that include (merge) all the updates from {@code updates}.
     */
    public static PartitionUpdate merge(List<PartitionUpdate> updates)
    {
        assert !updates.isEmpty();
        final int size = updates.size();

        if (size == 1)
            return Iterables.getOnlyElement(updates);

        List<UnfilteredRowIterator> asIterators = Lists.transform(updates, AbstractBTreePartition::unfilteredIterator);
        return fromIterator(UnfilteredRowIterators.merge(asIterators), ColumnFilter.all(updates.get(0).metadata()));
    }

    // We override this, because the version in the super-class calls holder(), which build the update preventing
    // further updates, but that's not necessary here and being able to check at least the partition deletion without
    // "locking" the update is nice (and used in DataResolver.RepairMergeListener.MergeListener).
    @Override
    public DeletionInfo deletionInfo()
    {
        return deletionInfo;
    }

    /**
     * The number of "operations" contained in the update.
     * <p>
     * This is used by {@code Memtable} to approximate how much work this update does. In practice, this
     * count how many rows are updated and how many ranges are deleted by the partition update.
     *
     * @return the number of "operations" performed by the update.
     */
    public int operationCount()
    {
        return rowCount()
             + (staticRow().isEmpty() ? 0 : 1)
             + deletionInfo.rangeCount()
             + (deletionInfo.getPartitionDeletion().isLive() ? 0 : 1);
    }

    /**
     * The size of the data contained in this update.
     *
     * @return the size of the data contained in this update.
     */
    public int dataSize()
    {
        return Ints.saturatedCast(BTree.<Row>accumulate(holder.tree, (row, value) -> row.dataSize() + value, 0L)
                + holder.staticRow.dataSize() + holder.deletionInfo.dataSize());
    }

    /**
     * The size of the data contained in this update.
     *
     * @return the size of the data contained in this update.
     */
    public long unsharedHeapSize()
    {
        return BTree.<Row>accumulate(holder.tree, (row, value) -> row.unsharedHeapSize() + value, 0L)
                + holder.staticRow.unsharedHeapSize() + holder.deletionInfo.unsharedHeapSize();
    }

    public TableMetadata metadata()
    {
        return metadata;
    }

    @Override
    public RegularAndStaticColumns columns()
    {
        // The superclass implementation calls holder(), but that triggers a build of the PartitionUpdate. But since
        // the columns are passed to the ctor, we know the holder always has the proper columns even if it doesn't have
        // the built rows yet, so just bypass the holder() method.
        return holder.columns;
    }

    protected BTreePartitionData holder()
    {
        return holder;
    }

    public EncodingStats stats()
    {
        return holder().stats;
    }

    /**
     * Validates the data contained in this update.
     *
     * @throws org.apache.cassandra.serializers.MarshalException if some of the data contained in this update is corrupted.
     */
    public void validate()
    {
        for (Row row : this)
        {
            metadata().comparator.validate(row.clustering());
            for (ColumnData cd : row)
                cd.validate();
        }
    }

    /**
     * The maximum timestamp used in this update.
     *
     * @return the maximum timestamp used in this update.
     */
    public long maxTimestamp()
    {
        long maxTimestamp = deletionInfo.maxTimestamp();
        for (Row row : this)
        {
            maxTimestamp = Math.max(maxTimestamp, row.primaryKeyLivenessInfo().timestamp());
            for (ColumnData cd : row)
            {
                if (cd.column().isSimple())
                {
                    maxTimestamp = Math.max(maxTimestamp, ((Cell<?>)cd).timestamp());
                }
                else
                {
                    ComplexColumnData complexData = (ComplexColumnData)cd;
                    maxTimestamp = Math.max(maxTimestamp, complexData.complexDeletion().markedForDeleteAt());
                    for (Cell<?> cell : complexData)
                        maxTimestamp = Math.max(maxTimestamp, cell.timestamp());
                }
            }
        }

        if (this.holder.staticRow != null)
        {
            for (ColumnData cd : this.holder.staticRow.columnData())
            {
                if (cd.column().isSimple())
                {
                    maxTimestamp = Math.max(maxTimestamp, ((Cell<?>) cd).timestamp());
                }
                else
                {
                    ComplexColumnData complexData = (ComplexColumnData) cd;
                    maxTimestamp = Math.max(maxTimestamp, complexData.complexDeletion().markedForDeleteAt());
                    for (Cell<?> cell : complexData)
                        maxTimestamp = Math.max(maxTimestamp, cell.timestamp());
                }
            }
        }
        return maxTimestamp;
    }

    /**
     * For an update on a counter table, returns a list containing a {@code CounterMark} for
     * every counter contained in the update.
     *
     * @return a list with counter marks for every counter in this update.
     */
    public List<CounterMark> collectCounterMarks()
    {
        assert metadata().isCounter();
        // We will take aliases on the rows of this update, and update them in-place. So we should be sure the
        // update is now immutable for all intent and purposes.
        List<CounterMark> marks = new ArrayList<>();
        addMarksForRow(staticRow(), marks);
        for (Row row : this)
            addMarksForRow(row, marks);
        return marks;
    }

    /**
     *
     * @return the estimated number of rows affected by this mutation 
     */
    public int affectedRowCount()
    {
        // If there is a partition-level deletion, we intend to delete at least one row.
        if (!partitionLevelDeletion().isLive())
            return 1;

        int count = 0;

        // Each range delete should correspond to at least one intended row deletion.
        if (deletionInfo().hasRanges())
            count += deletionInfo().rangeCount();

        count += rowCount();

        if (!staticRow().isEmpty())
            count++;

        return count;
    }

    /**
     *
     * @return the estimated total number of columns that either have live data or are covered by a delete
     */
    public int affectedColumnCount()
    {
        // If there is a partition-level deletion, we intend to delete at least the columns of one row.
        if (!partitionLevelDeletion().isLive())
            return metadata().regularAndStaticColumns().size();

        int count = 0;

        // Each range delete should correspond to at least one intended row deletion, and with it, its regular columns.
        if (deletionInfo().hasRanges())
            count += deletionInfo().rangeCount() * metadata().regularColumns().size();

        for (Row row : this)
        {
            if (row.deletion().isLive())
                // If the row is live, this will include simple tombstones as well as cells w/ actual data. 
                count += row.columnCount();
            else
                // We have a row deletion, so account for the columns that might be deleted.
                count += metadata().regularColumns().size();
        }

        if (!staticRow().isEmpty())
            count += staticRow().columnCount();

        return count;
    }

    private static void addMarksForRow(Row row, List<CounterMark> marks)
    {
        for (Cell<?> cell : row.cells())
        {
            if (cell.isCounterCell())
                marks.add(new CounterMark(row, cell.column(), cell.path()));
        }
    }

    /**
     * Creates a new simple partition update builder.
     *
     * @param metadata the metadata for the table this is a partition of.
     * @param partitionKeyValues the values for partition key columns identifying this partition. The values for each
     * partition key column can be passed either directly as {@code ByteBuffer} or using a "native" value (int for
     * Int32Type, string for UTF8Type, ...). It is also allowed to pass a single {@code DecoratedKey} value directly.
     * @return a newly created builder.
     */
    public static SimpleBuilder simpleBuilder(TableMetadata metadata, Object... partitionKeyValues)
    {
        return new SimpleBuilders.PartitionUpdateBuilder(metadata, partitionKeyValues);
    }

    public void validateIndexedColumns()
    {
        IndexRegistry.obtain(metadata()).validate(this);
    }

    @VisibleForTesting
    public static PartitionUpdate unsafeConstruct(TableMetadata metadata,
                                                  DecoratedKey key,
                                                  BTreePartitionData holder,
                                                  MutableDeletionInfo deletionInfo,
                                                  boolean canHaveShadowedData)
    {
        return new PartitionUpdate(metadata, key, holder, deletionInfo, canHaveShadowedData);
    }

    /**
     * Interface for building partition updates geared towards human.
     * <p>
     * This should generally not be used when performance matters too much, but provides a more convenient interface to
     * build an update than using the class constructor when performance is not of the utmost importance.
     */
    public interface SimpleBuilder
    {
        /**
         * The metadata of the table this is a builder on.
         */
        public TableMetadata metadata();

        /**
         * Sets the timestamp to use for the following additions to this builder or any derived (row) builder.
         *
         * @param timestamp the timestamp to use for following additions. If that timestamp hasn't been set, the current
         * time in microseconds will be used.
         * @return this builder.
         */
        public SimpleBuilder timestamp(long timestamp);

        /**
         * Sets the ttl to use for the following additions to this builder or any derived (row) builder.
         *
         * @param ttl the ttl to use for following additions. If that ttl hasn't been set, no ttl will be used.
         * @return this builder.
         */
        public SimpleBuilder ttl(int ttl);

        /**
         * Sets the current time to use for the following additions to this builder or any derived (row) builder.
         *
         * @param nowInSec the current time to use for following additions. If the current time hasn't been set, the current
         * time in seconds will be used.
         * @return this builder.
         */
        public SimpleBuilder nowInSec(long nowInSec);

        /**
         * Adds the row identifier by the provided clustering and return a builder for that row.
         *
         * @param clusteringValues the value for the clustering columns of the row to add to this build. There may be no
         * values if either the table has no clustering column, or if you want to edit the static row. Note that as a
         * shortcut it is also allowed to pass a {@code Clustering} object directly, in which case that should be the
         * only argument.
         * @return a builder for the row identified by {@code clusteringValues}.
         */
        public Row.SimpleBuilder row(Object... clusteringValues);

        /**
         * Deletes the partition identified by this builder (using a partition level deletion).
         *
         * @return this builder.
         */
        public SimpleBuilder delete();

        /**
         * Adds a new range tombstone to this update, returning a builder for that range.
         *
         * @return the range tombstone builder for the newly added range.
         */
        public RangeTombstoneBuilder addRangeTombstone();

        /**
         * Adds a new range tombstone to this update
         *
         * @return this builder
         */
        public SimpleBuilder addRangeTombstone(RangeTombstone rt);

        /**
         * Build the update represented by this builder.
         *
         * @return the built update.
         */
        public PartitionUpdate build();

        /**
         * As shortcut for {@code new Mutation(build())}.
         *
         * @return the built update, wrapped in a {@code Mutation}.
         */
        public Mutation buildAsMutation();

        /**
         * Interface to build range tombstone.
         *
         * By default, if no other methods are called, the represented range is inclusive of both start and end and
         * includes everything (its start is {@code BOTTOM} and it's end is {@code TOP}).
         */
        public interface RangeTombstoneBuilder
        {
            /**
             * Sets the start for the built range using the provided values.
             *
             * @param values the value for the start of the range. They act like the {@code clusteringValues} argument
             * of the {@link SimpleBuilder#row(Object...)} method, except that it doesn't have to be a full
             * clustering, it can only be a prefix.
             * @return this builder.
             */
            public RangeTombstoneBuilder start(Object... values);

            /**
             * Sets the end for the built range using the provided values.
             *
             * @param values the value for the end of the range. They act like the {@code clusteringValues} argument
             * of the {@link SimpleBuilder#row(Object...)} method, except that it doesn't have to be a full
             * clustering, it can only be a prefix.
             * @return this builder.
             */
            public RangeTombstoneBuilder end(Object... values);

            /**
             * Sets the start of this range as inclusive.
             * <p>
             * This is the default and don't need to be called, but can for explicitness.
             *
             * @return this builder.
             */
            public RangeTombstoneBuilder inclStart();

            /**
             * Sets the start of this range as exclusive.
             *
             * @return this builder.
             */
            public RangeTombstoneBuilder exclStart();

            /**
             * Sets the end of this range as inclusive.
             * <p>
             * This is the default and don't need to be called, but can for explicitness.
             *
             * @return this builder.
             */
            public RangeTombstoneBuilder inclEnd();

            /**
             * Sets the end of this range as exclusive.
             *
             * @return this builder.
             */
            public RangeTombstoneBuilder exclEnd();
        }
    }

    public static class PartitionUpdateSerializer
    {
        public void serialize(PartitionUpdate update, DataOutputPlus out, int version) throws IOException
        {
            try (UnfilteredRowIterator iter = update.unfilteredIterator())
            {
                assert !iter.isReverseOrder();

                update.metadata.id.serialize(out);
                UnfilteredRowIteratorSerializer.serializer.serialize(iter, null, out, version, update.rowCount());
            }
        }

        public PartitionUpdate deserialize(DataInputPlus in, int version, DeserializationHelper.Flag flag) throws IOException
        {
            TableMetadata metadata = Schema.instance.getExistingTableMetadata(TableId.deserialize(in));
            UnfilteredRowIteratorSerializer.Header header = UnfilteredRowIteratorSerializer.serializer.deserializeHeader(metadata, null, in, version, flag);
            if (header.isEmpty)
                return emptyUpdate(metadata, header.key);

            assert !header.isReversed;
            assert header.rowEstimate >= 0;

            MutableDeletionInfo.Builder deletionBuilder = MutableDeletionInfo.builder(header.partitionDeletion, metadata.comparator, false);
            Object[] rows;
            try (BTree.FastBuilder<Row> builder = BTree.fastBuilder();
                 UnfilteredRowIterator partition = UnfilteredRowIteratorSerializer.serializer.deserialize(in, version, metadata, flag, header))
            {
                while (partition.hasNext())
                {
                    Unfiltered unfiltered = partition.next();
                    if (unfiltered.kind() == Unfiltered.Kind.ROW)
                        builder.add((Row)unfiltered);
                    else
                        deletionBuilder.add((RangeTombstoneMarker)unfiltered);
                }
                rows = builder.build();
            }

            MutableDeletionInfo deletionInfo = deletionBuilder.build();
            return new PartitionUpdate(metadata,
                                       header.key,
                                       new BTreePartitionData(header.sHeader.columns(), rows, deletionInfo, header.staticRow, header.sHeader.stats()),
                                       deletionInfo,
                                       false);
        }

        public static boolean isEmpty(ByteBuffer in, DeserializationHelper.Flag flag, DecoratedKey key) throws IOException
        {
            int position = in.position();
            position += 16; // CFMetaData.serializer.deserialize(in, version);
            if (position >= in.limit())
                throw new EOFException();
            // DecoratedKey key = metadata.decorateKey(ByteBufferUtil.readWithVIntLength(in));
            int keyLength = VIntCoding.getUnsignedVInt32(in, position);
            position += keyLength + VIntCoding.computeUnsignedVIntSize(keyLength);
            if (position >= in.limit())
                throw new EOFException();
            int flags = in.get(position) & 0xff;
            return (flags & IS_EMPTY) != 0;
        }

        public long serializedSize(PartitionUpdate update, int version)
        {
            try (UnfilteredRowIterator iter = update.unfilteredIterator())
            {
                return update.metadata.id.serializedSize()
                     + UnfilteredRowIteratorSerializer.serializer.serializedSize(iter, null, version, update.rowCount());
            }
        }
    }

    /**
     * A counter mark is basically a pointer to a counter update inside this partition update. That pointer allows
     * us to update the counter value based on the pre-existing value read during the read-before-write that counters
     * do. See {@link CounterMutation} to understand how this is used.
     */
    public static class CounterMark
    {
        private final Row row;
        private final ColumnMetadata column;
        private final CellPath path;

        private CounterMark(Row row, ColumnMetadata column, CellPath path)
        {
            this.row = row;
            this.column = column;
            this.path = path;
        }

        public Clustering<?> clustering()
        {
            return row.clustering();
        }

        public ColumnMetadata column()
        {
            return column;
        }

        public CellPath path()
        {
            return path;
        }

        public ByteBuffer value()
        {
            return path == null
                 ? row.getCell(column).buffer()
                 : row.getCell(column, path).buffer();
        }

        public void setValue(ByteBuffer value)
        {
            // This is a bit of a giant hack as this is the only place where we mutate a Row object. This makes it more efficient
            // for counters however and this won't be needed post-#6506 so that's probably fine.
            assert row instanceof BTreeRow;
            ((BTreeRow)row).setValue(column, path, value);
        }
    }

    /**
     * Builder for PartitionUpdates
     *
     * This class is not thread safe, but the PartitionUpdate it produces is (since it is immutable).
     */
    public static class Builder
    {
        private final TableMetadata metadata;
        private final DecoratedKey key;
        private final MutableDeletionInfo deletionInfo;
        private final boolean canHaveShadowedData;
        private Object[] tree = BTree.empty();
        private final BTree.Builder<Row> rowBuilder;
        private Row staticRow = Rows.EMPTY_STATIC_ROW;
        private final RegularAndStaticColumns columns;
        private boolean isBuilt = false;

        public Builder(TableMetadata metadata,
                       DecoratedKey key,
                       RegularAndStaticColumns columns,
                       int initialRowCapacity,
                       boolean canHaveShadowedData)
        {
            this(metadata, key, columns, initialRowCapacity, canHaveShadowedData, Rows.EMPTY_STATIC_ROW, MutableDeletionInfo.live(), BTree.empty());
        }

        private Builder(TableMetadata metadata,
                       DecoratedKey key,
                       RegularAndStaticColumns columns,
                       int initialRowCapacity,
                       boolean canHaveShadowedData,
                       BTreePartitionData holder)
        {
            this(metadata, key, columns, initialRowCapacity, canHaveShadowedData, holder.staticRow, holder.deletionInfo, holder.tree);
        }

        private Builder(TableMetadata metadata,
                        DecoratedKey key,
                        RegularAndStaticColumns columns,
                        int initialRowCapacity,
                        boolean canHaveShadowedData,
                        Row staticRow,
                        DeletionInfo deletionInfo,
                        Object[] tree)
        {
            this.metadata = metadata;
            this.key = key;
            this.columns = columns;
            this.rowBuilder = rowBuilder(initialRowCapacity);
            this.canHaveShadowedData = canHaveShadowedData;
            this.deletionInfo = deletionInfo.mutableCopy();
            this.staticRow = staticRow;
            this.tree = tree;
        }

        public Builder(TableMetadata metadata, DecoratedKey key, RegularAndStaticColumns columnDefinitions, int size)
        {
            this(metadata, key, columnDefinitions, size, true);
        }

        public Builder(PartitionUpdate base, int initialRowCapacity)
        {
            this(base.metadata, base.partitionKey, base.columns(), initialRowCapacity, base.canHaveShadowedData, base.holder);
        }

        public Builder(TableMetadata metadata,
                        ByteBuffer key,
                        RegularAndStaticColumns columns,
                        int initialRowCapacity)
        {
            this(metadata, metadata.partitioner.decorateKey(key), columns, initialRowCapacity, true);
        }

        /**
         * Adds a row to this update.
         *
         * There is no particular assumption made on the order of row added to a partition update. It is further
         * allowed to add the same row (more precisely, multiple row objects for the same clustering).
         *
         * Note however that the columns contained in the added row must be a subset of the columns used when
         * creating this update.
         *
         * @param row the row to add.
         */
        public void add(Row row)
        {
            if (row.isEmpty())
                return;

            if (row.isStatic())
            {
                // this assert is expensive, and possibly of limited value; we should consider removing it
                // or introducing a new class of assertions for test purposes
                assert columns().statics.containsAll(row.columns()) : columns().statics + " is not superset of " + row.columns();
                staticRow = staticRow.isEmpty()
                            ? row
                            : Rows.merge(staticRow, row);
            }
            else
            {
                // this assert is expensive, and possibly of limited value; we should consider removing it
                // or introducing a new class of assertions for test purposes
                assert columns().regulars.containsAll(row.columns()) : columns().regulars + " is not superset of " + row.columns();
                rowBuilder.add(row);
            }
        }

        public void addPartitionDeletion(DeletionTime deletionTime)
        {
            deletionInfo.add(deletionTime);
        }

        public void add(RangeTombstone range)
        {
            deletionInfo.add(range, metadata.comparator);
        }

        public DecoratedKey partitionKey()
        {
            return key;
        }

        public TableMetadata metadata()
        {
            return metadata;
        }

        public PartitionUpdate build()
        {
            // assert that we are not calling build() several times
            assert !isBuilt : "A PartitionUpdate.Builder should only get built once";
            Object[] add = rowBuilder.build();
            Object[] merged = BTree.<Row, Row, Row>update(tree, add, metadata.comparator,
                                                          UpdateFunction.Simple.of(Rows::merge));

            EncodingStats newStats = EncodingStats.Collector.collect(staticRow, BTree.iterator(merged), deletionInfo);

            isBuilt = true;
            return new PartitionUpdate(metadata,
                                       partitionKey(),
                                       new BTreePartitionData(columns,
                                                              merged,
                                                              deletionInfo,
                                                              staticRow,
                                                              newStats),
                                       deletionInfo,
                                       canHaveShadowedData);
        }

        public RegularAndStaticColumns columns()
        {
            return columns;
        }

        public DeletionTime partitionLevelDeletion()
        {
            return deletionInfo.getPartitionDeletion();
        }

        private BTree.Builder<Row> rowBuilder(int initialCapacity)
        {
            return BTree.<Row>builder(metadata.comparator, initialCapacity)
                   .setQuickResolver(Rows::merge);
        }
        /**
         * Modify this update to set every timestamp for live data to {@code newTimestamp} and
         * every deletion timestamp to {@code newTimestamp - 1}.
         *
         * There is no reason to use that expect on the Paxos code path, where we need ensure that
         * anything inserted use the ballot timestamp (to respect the order of update decided by
         * the Paxos algorithm). We use {@code newTimestamp - 1} for deletions because tombstones
         * always win on timestamp equality and we don't want to delete our own insertions
         * (typically, when we overwrite a collection, we first set a complex deletion to delete the
         * previous collection before adding new elements. If we were to set that complex deletion
         * to the same timestamp that the new elements, it would delete those elements). And since
         * tombstones always wins on timestamp equality, using -1 guarantees our deletion will still
         * delete anything from a previous update.
         */
        public Builder updateAllTimestamp(long newTimestamp)
        {
            deletionInfo.updateAllTimestamp(newTimestamp - 1);
            tree = BTree.<Row, Row>transformAndFilter(tree, (x) -> x.updateAllTimestamp(newTimestamp));
            staticRow = this.staticRow.updateAllTimestamp(newTimestamp);
            return this;
        }

        @Override
        public String toString()
        {
            return "Builder{" +
                   "metadata=" + metadata +
                   ", key=" + key +
                   ", deletionInfo=" + deletionInfo +
                   ", canHaveShadowedData=" + canHaveShadowedData +
                   ", staticRow=" + staticRow +
                   ", columns=" + columns +
                   ", isBuilt=" + isBuilt +
                   '}';
        }

    }
}
