exec/java-exec/src/main/java/org/apache/drill/exec/planner/logical/DrillSemiJoinRel.java

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 * Licensed to the Apache Software Foundation (ASF) under one
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 * 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
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 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
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package org.apache.drill.exec.planner.logical;

import org.apache.calcite.plan.RelOptCluster;
import org.apache.calcite.plan.RelOptCost;
import org.apache.calcite.plan.RelOptPlanner;
import org.apache.calcite.plan.RelTraitSet;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.core.JoinInfo;
import org.apache.calcite.rel.core.JoinRelType;
import org.apache.calcite.rel.metadata.RelMdUtil;
import org.apache.calcite.rel.metadata.RelMetadataQuery;
import org.apache.calcite.rex.RexNode;
import org.apache.calcite.util.Pair;
import org.apache.drill.common.expression.FieldReference;
import org.apache.drill.common.logical.data.Join;
import org.apache.drill.common.logical.data.JoinCondition;
import org.apache.drill.common.logical.data.LogicalOperator;
import org.apache.drill.common.logical.data.LogicalSemiJoin;
import org.apache.drill.exec.planner.common.DrillJoinRelBase;
import com.google.common.collect.Lists;
import com.google.common.base.Preconditions;

import java.util.ArrayList;
import java.util.List;

public class DrillSemiJoinRel extends DrillJoinRelBase implements DrillJoin, DrillRel {

  public DrillSemiJoinRel(
          RelOptCluster cluster,
          RelTraitSet traitSet,
          RelNode left,
          RelNode right,
          RexNode condition,
          List<Integer> leftKeys,
          List<Integer> rightKeys) {
    super(cluster,
          traitSet,
          left,
          right,
          condition,
          JoinRelType.SEMI);
    this.leftKeys = leftKeys;
    this.rightKeys = rightKeys;
  }

  public static DrillSemiJoinRel create(RelNode left, RelNode right, RexNode condition,
                                        List<Integer> leftKeys, List<Integer> rightKeys) {
    final RelOptCluster cluster = left.getCluster();
    return new DrillSemiJoinRel(cluster, cluster.traitSetOf(DrillRel.DRILL_LOGICAL), left,
            right, condition, leftKeys, rightKeys);
  }

  @Override
  public DrillSemiJoinRel copy(RelTraitSet traitSet, RexNode condition,
                                 RelNode left, RelNode right, JoinRelType joinType, boolean semiJoinDone) {
    Preconditions.checkArgument(joinType == JoinRelType.SEMI);
    final JoinInfo joinInfo = JoinInfo.of(left, right, condition);
    Preconditions.checkArgument(joinInfo.isEqui());
    return new DrillSemiJoinRel(getCluster(), traitSet, left, right, condition,
            joinInfo.leftKeys, joinInfo.rightKeys);
  }

  @Override
  public LogicalOperator implement(DrillImplementor implementor) {
    List<String> fields = new ArrayList<>();
    fields.addAll(getInput(0).getRowType().getFieldNames());
    fields.addAll(getInput(1).getRowType().getFieldNames());
    Preconditions.checkArgument(DrillJoinRel.isUnique(fields));
    final int leftCount = left.getRowType().getFieldCount();
    final List<String> leftFields = fields.subList(0, leftCount);
    final List<String> rightFields = fields.subList(leftCount, leftCount + right.getRowType().getFieldCount());

    final LogicalOperator leftOp = DrillJoinRel.implementInput(implementor, 0, 0, left, this, fields);
    final LogicalOperator rightOp = DrillJoinRel.implementInput(implementor, 1, leftCount, right, this, fields);

    Join.Builder builder = Join.builder();
    builder.type(joinType);
    builder.left(leftOp);
    builder.right(rightOp);
    List<JoinCondition> conditions = Lists.newArrayList();
    for (Pair<Integer, Integer> pair : Pair.zip(leftKeys, rightKeys)) {
      conditions.add(new JoinCondition(DrillJoinRel.EQUALITY_CONDITION,
              new FieldReference(leftFields.get(pair.left)), new FieldReference(rightFields.get(pair.right))));
    }

    return new LogicalSemiJoin(leftOp, rightOp, conditions, joinType);
  }

  @Override
  public RelOptCost computeSelfCost(RelOptPlanner planner, RelMetadataQuery mq) {
    return computeLogicalJoinCost(planner, mq);
  }

  @Override
  public double estimateRowCount(RelMetadataQuery mq) {
    RexNode semiJoinSelectivity =
      RelMdUtil.makeSemiJoinSelectivityRexNode(mq, this);
    Double selectivity = mq.getSelectivity(getLeft(), semiJoinSelectivity);
    return selectivity * mq.getRowCount(getLeft());
  }
}