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.linq4j.function.Experimental;
  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.tools.RelBuilder;
  
  import org.immutables.value.Value;
  
  /** Rule that re-orders a {@link Join} tree using dphyp algorithm.
   *
   * @see CoreRules#HYPER_GRAPH_OPTIMIZE */
  @Value.Enclosing
  @Experimental
  public class DphypJoinReorderRule
      extends RelRule<DphypJoinReorderRule.Config>
      implements TransformationRule {
  
    protected DphypJoinReorderRule(Config config) {
      super(config);
    }
  
    @Override public void onMatch(RelOptRuleCall call) {
      HyperGraph hyperGraph = call.rel(0);
      RelBuilder relBuilder = call.builder();
  
      // enumerate by Dphyp
      DpHyp dpHyp = new DpHyp(hyperGraph, relBuilder, call.getMetadataQuery(), config.bloat());
      dpHyp.startEnumerateJoin();
      RelNode orderedJoin = dpHyp.getBestPlan();
      if (orderedJoin == null) {
        return;
      }
      call.transformTo(orderedJoin);
    }
  
    /** Rule configuration. */
    @Value.Immutable
    public interface Config extends RelRule.Config {
      Config DEFAULT = ImmutableDphypJoinReorderRule.Config.of()
          .withOperandSupplier(b1 ->
              b1.operand(HyperGraph.class).anyInputs());
  
      @Override default DphypJoinReorderRule toRule() {
        return new DphypJoinReorderRule(this);
      }
  
      /**
       * Limit to the size growth of the dpTable allowed during enumerating.
       * If the graph with n inputs is fully connected and any combination is legal, the size of
       * dpTable is 2^n-1. The default value assumes n=7.
       */
      default int bloat() {
        return 127;
      }
    }
  }
  