content: /*
   * 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.adapter.enumerable;
  
  import org.apache.calcite.plan.Convention;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.convert.ConverterRule;
  import org.apache.calcite.rel.core.Join;
  import org.apache.calcite.rel.core.JoinInfo;
  import org.apache.calcite.rel.logical.LogicalJoin;
  import org.apache.calcite.rex.RexBuilder;
  import org.apache.calcite.rex.RexNode;
  import org.apache.calcite.rex.RexUtil;
  
  import java.util.ArrayList;
  import java.util.Arrays;
  import java.util.List;
  
  /** Planner rule that converts a
   * {@link LogicalJoin} relational expression
   * {@link org.apache.calcite.adapter.enumerable.EnumerableConvention enumerable calling convention}.
   * You may provide a custom config to convert other nodes that extend {@link Join}.
   *
   * @see EnumerableRules#ENUMERABLE_JOIN_RULE */
  class EnumerableJoinRule extends ConverterRule {
    /** Default configuration. */
    public static final Config DEFAULT_CONFIG = Config.INSTANCE
        .withConversion(LogicalJoin.class, Convention.NONE,
            EnumerableConvention.INSTANCE, "EnumerableJoinRule")
        .withRuleFactory(EnumerableJoinRule::new);
  
    /** Called from the Config. */
    protected EnumerableJoinRule(Config config) {
      super(config);
    }
  
    @Override public RelNode convert(RelNode rel) {
      Join join = (Join) rel;
      List<RelNode> newInputs = new ArrayList<>();
      for (RelNode input : join.getInputs()) {
        if (!(input.getConvention() instanceof EnumerableConvention)) {
          input =
              convert(
                  input,
                  input.getTraitSet()
                      .replace(EnumerableConvention.INSTANCE));
        }
        newInputs.add(input);
      }
      final RexBuilder rexBuilder = join.getCluster().getRexBuilder();
      final RelNode left = newInputs.get(0);
      final RelNode right = newInputs.get(1);
      final JoinInfo info = join.analyzeCondition();
  
      // If the join has equiKeys (i.e. complete or partial equi-join),
      // create an EnumerableHashJoin, which supports all types of joins,
      // even if the join condition contains partial non-equi sub-conditions;
      // otherwise (complete non-equi-join), create an EnumerableNestedLoopJoin,
      // since a hash join strategy in this case would not be beneficial.
      final boolean hasEquiKeys = !info.leftKeys.isEmpty()
          && !info.rightKeys.isEmpty();
      if (hasEquiKeys) {
        // Re-arrange condition: first the equi-join elements, then the non-equi-join ones (if any);
        // this is not strictly necessary but it will be useful to avoid spurious errors in the
        // unit tests when verifying the plan.
        final RexNode equi = info.getEquiCondition(left, right, rexBuilder);
        final RexNode condition;
        if (info.isEqui()) {
          condition = equi;
        } else {
          final RexNode nonEqui = RexUtil.composeConjunction(rexBuilder, info.nonEquiConditions);
          condition = RexUtil.composeConjunction(rexBuilder, Arrays.asList(equi, nonEqui));
        }
        return EnumerableHashJoin.create(
            left,
            right,
            condition,
            join.getVariablesSet(),
            join.getJoinType());
      }
      return EnumerableNestedLoopJoin.create(
          left,
          right,
          join.getCondition(),
          join.getVariablesSet(),
          join.getJoinType());
    }
  }
  