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.core.Join;
  import org.apache.calcite.rel.logical.LogicalJoin;
  import org.apache.calcite.tools.RelBuilderFactory;
  
  import org.immutables.value.Value;
  
  /**
   * Planner rule that removes a {@link Join#isSemiJoin semi-join} from a join
   * tree.
   *
   * <p>It is invoked after attempts have been made to convert a SemiJoin to an
   * indexed scan on a join factor have failed. Namely, if the join factor does
   * not reduce to a single table that can be scanned using an index.
   *
   * <p>It should only be enabled if all SemiJoins in the plan are advisory; that
   * is, they can be safely dropped without affecting the semantics of the query.
   *
   * @see CoreRules#SEMI_JOIN_REMOVE
   */
  @Value.Enclosing
  public class SemiJoinRemoveRule
      extends RelRule<SemiJoinRemoveRule.Config>
      implements TransformationRule {
  
    /** Creates a SemiJoinRemoveRule. */
    protected SemiJoinRemoveRule(Config config) {
      super(config);
    }
  
    @Deprecated // to be removed before 2.0
    public SemiJoinRemoveRule(RelBuilderFactory relBuilderFactory) {
      this(Config.DEFAULT.withRelBuilderFactory(relBuilderFactory)
          .as(Config.class));
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public void onMatch(RelOptRuleCall call) {
      call.transformTo(call.rel(0).getInput(0));
    }
  
    /** Rule configuration. */
    @Value.Immutable
    public interface Config extends RelRule.Config {
      Config DEFAULT = ImmutableSemiJoinRemoveRule.Config.of()
          .withOperandFor(LogicalJoin.class);
  
      @Override default SemiJoinRemoveRule toRule() {
        return new SemiJoinRemoveRule(this);
      }
  
      /** Defines an operand tree for the given classes. */
      default Config withOperandFor(Class<? extends Join> joinClass) {
        return withOperandSupplier(b ->
            b.operand(joinClass).predicate(Join::isSemiJoin).anyInputs())
            .as(Config.class);
      }
    }
  }
  