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.rel.rules;
  
  import org.apache.calcite.plan.RelOptRuleCall;
  import org.apache.calcite.plan.RelRule;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.Join;
  import org.apache.calcite.rel.core.JoinInfo;
  import org.apache.calcite.rel.core.JoinRelType;
  import org.apache.calcite.rel.logical.LogicalJoin;
  import org.apache.calcite.tools.RelBuilderFactory;
  
  import com.google.common.collect.ImmutableList;
  import com.google.common.collect.ImmutableSet;
  
  import org.immutables.value.Value;
  
  /**
   * Rule to add a semi-join into a join. Transformation is as follows:
   *
   * <p>LogicalJoin(X, Y) &rarr; LogicalJoin(SemiJoin(X, Y), Y)
   *
   * <p>Can be configured to match any sub-class of
   * {@link org.apache.calcite.rel.core.Join}, not just
   * {@link org.apache.calcite.rel.logical.LogicalJoin}.
   *
   * @see CoreRules#JOIN_ADD_REDUNDANT_SEMI_JOIN
   */
  @Value.Enclosing
  public class JoinAddRedundantSemiJoinRule
      extends RelRule<JoinAddRedundantSemiJoinRule.Config>
      implements TransformationRule {
  
    /** Creates a JoinAddRedundantSemiJoinRule. */
    protected JoinAddRedundantSemiJoinRule(Config config) {
      super(config);
    }
  
    @Deprecated // to be removed before 2.0
    public JoinAddRedundantSemiJoinRule(Class<? extends Join> clazz,
        RelBuilderFactory relBuilderFactory) {
      this(Config.DEFAULT.withRelBuilderFactory(relBuilderFactory)
          .as(Config.class)
          .withOperandFor(clazz));
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public void onMatch(RelOptRuleCall call) {
      Join origJoinRel = call.rel(0);
      if (origJoinRel.isSemiJoinDone()) {
        return;
      }
  
      // can't process outer joins using semi-joins
      if (origJoinRel.getJoinType() != JoinRelType.INNER) {
        return;
      }
  
      // determine if we have a valid join condition
      final JoinInfo joinInfo = origJoinRel.analyzeCondition();
      if (joinInfo.leftKeys.isEmpty()) {
        return;
      }
  
      RelNode semiJoin =
          LogicalJoin.create(origJoinRel.getLeft(),
              origJoinRel.getRight(),
              ImmutableList.of(),
              origJoinRel.getCondition(),
              ImmutableSet.of(),
              JoinRelType.SEMI);
  
      RelNode newJoinRel =
          origJoinRel.copy(
              origJoinRel.getTraitSet(),
              origJoinRel.getCondition(),
              semiJoin,
              origJoinRel.getRight(),
              JoinRelType.INNER,
              true);
  
      call.transformTo(newJoinRel);
    }
  
    /** Rule configuration. */
    @Value.Immutable
    public interface Config extends RelRule.Config {
      Config DEFAULT = ImmutableJoinAddRedundantSemiJoinRule.Config.of()
          .withOperandFor(LogicalJoin.class);
  
      @Override default JoinAddRedundantSemiJoinRule toRule() {
        return new JoinAddRedundantSemiJoinRule(this);
      }
  
      /** Defines an operand tree for the given classes. */
      default Config withOperandFor(Class<? extends Join> joinClass) {
        return withOperandSupplier(b -> b.operand(joinClass).anyInputs())
            .as(Config.class);
      }
    }
  }
  