CommonRelSubExprRegisterRule.java

/*
 * 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.CommonRelExpressionRegistry;
import org.apache.calcite.plan.CommonRelSubExprRule;
import org.apache.calcite.plan.RelOptRuleCall;
import org.apache.calcite.rel.RelNode;
import org.apache.calcite.rel.core.Aggregate;
import org.apache.calcite.rel.core.Filter;
import org.apache.calcite.rel.core.Join;
import org.apache.calcite.rel.core.JoinRelType;
import org.apache.calcite.rel.core.Project;
import org.apache.calcite.rel.metadata.RelMetadataQuery;

import com.google.common.collect.Multimap;

import org.immutables.value.Value;

import java.util.function.Predicate;

/**
 * Rule for saving relational expressions that appear more than once in a query tree to the planner
 * context.
 */
@Value.Enclosing
public final class CommonRelSubExprRegisterRule extends CommonRelSubExprRule {

  private CommonRelSubExprRegisterRule(Config config) {
    super(config);
  }

  @Override public void onMatch(final RelOptRuleCall call) {
    CommonRelExpressionRegistry r =
        call.getPlanner().getContext().unwrap(CommonRelExpressionRegistry.class);
    if (r != null) {
      r.add(call.rel(0));
    }
  }

  /**
   * A predicate determining if a relational expression is interesting.
   *
   * <p>The notion of interesting is loosely defined on purpose since it may change as the API
   * evolves. At the moment an expression is considered interesting if it contains at least one of
   * the following RelNode types:
   * <ul>
   *   <li>{@link Join}</li>
   *   <li>{@link Aggregate}</li>
   *   <li>{@link Filter}</li>
   * </ul>
   */
  private static final class InterestingRelNodePredicate implements Predicate<RelNode> {
    @Override public boolean test(final RelNode rel) {
      RelMetadataQuery mq = rel.getCluster().getMetadataQuery();
      Multimap<Class<? extends RelNode>, RelNode> types = mq.getNodeTypes(rel);
      if (types == null) {
        return false;
      }
      return types.keySet().stream().anyMatch(
          t -> Join.class.isAssignableFrom(t) || Aggregate.class.isAssignableFrom(t)
              || Filter.class.isAssignableFrom(t));
    }
  }

  /** Rule configuration. */
  @Value.Immutable
  public interface Config extends CommonRelSubExprRule.Config {
    Config JOIN = ImmutableCommonRelSubExprRegisterRule.Config.builder()
        .withOperandSupplier(o -> o.operand(Join.class)
            .predicate(j -> JoinRelType.INNER == j.getJoinType()).anyInputs())
        .build();
    Config AGGREGATE = ImmutableCommonRelSubExprRegisterRule.Config.builder()
        .withOperandSupplier(o -> o.operand(Aggregate.class).anyInputs()).build();

    Config FILTER = ImmutableCommonRelSubExprRegisterRule.Config.builder()
        .withOperandSupplier(o -> o.operand(Filter.class).anyInputs()).build();

    Config PROJECT = ImmutableCommonRelSubExprRegisterRule.Config.builder()
        .withOperandSupplier(o -> o.operand(Project.class)
            .predicate(new InterestingRelNodePredicate()).anyInputs())
        .build();

    @Override default CommonRelSubExprRegisterRule toRule() {
      return new CommonRelSubExprRegisterRule(this);
    }
  }

}