/*
 * Copyright 2019-2021 The Polypheny Project
 *
 * Licensed 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.
 *
 * This file incorporates code covered by the following terms:
 *
 * 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.polypheny.db.plan;


/**
 * RelOptSamplingParameters represents the parameters necessary to produce a sample of a relation.
 *
 * It's parameters are derived from the SQL 2003 TABLESAMPLE clause.
 */
public class AlgOptSamplingParameters {

    private final boolean isBernoulli;
    private final float samplingPercentage;
    private final boolean isRepeatable;
    private final int repeatableSeed;


    public AlgOptSamplingParameters( boolean isBernoulli, float samplingPercentage, boolean isRepeatable, int repeatableSeed ) {
        this.isBernoulli = isBernoulli;
        this.samplingPercentage = samplingPercentage;
        this.isRepeatable = isRepeatable;
        this.repeatableSeed = repeatableSeed;
    }


    /**
     * Indicates whether Bernoulli or system sampling should be performed. Bernoulli sampling requires the decision whether to include each row in the sample to be independent
     * across rows. System sampling allows implementation-dependent behavior.
     *
     * @return true if Bernoulli sampling is configured, false for system sampling
     */
    public boolean isBernoulli() {
        return isBernoulli;
    }


    /**
     * Returns the sampling percentage. For Bernoulli sampling, the sampling percentage is the likelihood that any given row will be included in the sample. For system sampling,
     * the sampling percentage indicates (roughly) what percentage of the rows will appear in the sample.
     *
     * @return the sampling percentage between 0.0 and 1.0, exclusive
     */
    public float getSamplingPercentage() {
        return samplingPercentage;
    }


    /**
     * Indicates whether the sample results should be repeatable. Sample results are only required to repeat if no changes have been made to the relation's content or structure.
     * If the sample is configured to be repeatable, then a user-specified seed value can be obtained via {@link #getRepeatableSeed()}.
     *
     * @return true if the sample results should be repeatable
     */
    public boolean isRepeatable() {
        return isRepeatable;
    }


    /**
     * If {@link #isRepeatable()} returns <code>true</code>, this method returns a user-specified seed value. Samples of the same, unmodified relation should be identical if the
     * sampling mode, sampling percentage and repeatable seed are the same.
     *
     * @return seed value for repeatable samples
     */
    public int getRepeatableSeed() {
        return repeatableSeed;
    }

}

