/*
 * 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.eigenbase.rel;

import java.util.List;

import org.eigenbase.relopt.*;

/**
 * SamplingRel represents the TABLESAMPLE BERNOULLI or SYSTEM keyword applied to
 * a table, view or subquery.
 */
public class SamplingRel extends SingleRel {
  //~ Instance fields --------------------------------------------------------

  private final RelOptSamplingParameters params;

  //~ Constructors -----------------------------------------------------------

  public SamplingRel(
      RelOptCluster cluster,
      RelNode child,
      RelOptSamplingParameters params) {
    super(
        cluster,
        cluster.traitSetOf(Convention.NONE),
        child);
    this.params = params;
  }

  /**
   * Creates a SamplingRel by parsing serialized output.
   */
  public SamplingRel(RelInput input) {
    this(
        input.getCluster(), input.getInput(), getSamplingParameters(input));
  }

  //~ Methods ----------------------------------------------------------------

  private static RelOptSamplingParameters getSamplingParameters(
      RelInput input) {
    String mode = input.getString("mode");
    float percentage = input.getFloat("rate");
    Object repeatableSeed = input.get("repeatableSeed");
    boolean repeatable = repeatableSeed instanceof Number;
    return new RelOptSamplingParameters(
        mode.equals("bernoulli"), percentage, repeatable,
        repeatable ? ((Number) repeatableSeed).intValue() : 0);
  }

  public RelNode copy(RelTraitSet traitSet, List<RelNode> inputs) {
    assert traitSet.containsIfApplicable(Convention.NONE);
    return new SamplingRel(
        getCluster(),
        sole(inputs),
        params);
  }

  /**
   * Retrieve the sampling parameters for this SamplingRel.
   */
  public RelOptSamplingParameters getSamplingParameters() {
    return params;
  }

  // implement RelNode
  public RelWriter explainTerms(RelWriter pw) {
    return super.explainTerms(pw)
        .item("mode", params.isBernoulli() ? "bernoulli" : "system")
        .item("rate", params.getSamplingPercentage())
        .item(
            "repeatableSeed",
            params.isRepeatable() ? params.getRepeatableSeed() : "-");
  }
}

// End SamplingRel.java