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.convert;
  
  import org.apache.calcite.plan.Convention;
  import org.apache.calcite.plan.RelOptRuleCall;
  import org.apache.calcite.plan.RelOptRuleOperand;
  import org.apache.calcite.plan.RelOptRuleOperandChildPolicy;
  import org.apache.calcite.plan.RelRule;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.RelFactories;
  import org.apache.calcite.tools.RelBuilderFactory;
  
  import org.checkerframework.checker.nullness.qual.Nullable;
  import org.immutables.value.Value;
  
  /**
   * TraitMatchingRule adapts a converter rule, restricting it to fire only when
   * its input already matches the expected output trait. This can be used with
   * {@link org.apache.calcite.plan.hep.HepPlanner} in cases where alternate
   * implementations are available and it is desirable to minimize converters.
   */
  @Value.Enclosing
  public class TraitMatchingRule extends RelRule<TraitMatchingRule.Config> {
    /**
     * Creates a configuration for a TraitMatchingRule.
     *
     * @param converterRule     Rule to be restricted; rule must take a single
     *                          operand expecting a single input
     * @param relBuilderFactory Builder for relational expressions
     */
    public static Config config(ConverterRule converterRule,
        RelBuilderFactory relBuilderFactory) {
      final RelOptRuleOperand operand = converterRule.getOperand();
      assert operand.childPolicy == RelOptRuleOperandChildPolicy.ANY;
      return ImmutableTraitMatchingRule.Config.builder().withRelBuilderFactory(relBuilderFactory)
          .withDescription("TraitMatchingRule: " + converterRule)
          .withOperandSupplier(b0 ->
              b0.operand(operand.getMatchedClass()).oneInput(b1 ->
                  b1.operand(RelNode.class).anyInputs()))
          .withConverterRule(converterRule)
          .build();
    }
  
    //~ Constructors -----------------------------------------------------------
  
    /** Creates a TraitMatchingRule. */
    protected TraitMatchingRule(Config config) {
      super(config);
    }
  
    @Deprecated // to be removed before 2.0
    public TraitMatchingRule(ConverterRule converterRule) {
      this(config(converterRule, RelFactories.LOGICAL_BUILDER));
    }
  
    @Deprecated // to be removed before 2.0
    public TraitMatchingRule(ConverterRule converterRule,
        RelBuilderFactory relBuilderFactory) {
      this(config(converterRule, relBuilderFactory));
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public @Nullable Convention getOutConvention() {
      return config.converterRule().getOutConvention();
    }
  
    @Override public void onMatch(RelOptRuleCall call) {
      RelNode input = call.rel(1);
      final ConverterRule converterRule = config.converterRule();
      if (input.getTraitSet().contains(converterRule.getOutTrait())) {
        converterRule.onMatch(call);
      }
    }
  
    /** Rule configuration. */
    @Value.Immutable(singleton = false)
    public interface Config extends RelRule.Config {
      @Override default TraitMatchingRule toRule() {
        return new TraitMatchingRule(this);
      }
  
      /** Returns the rule to be restricted; rule must take a single
       * operand expecting a single input. */
      ConverterRule converterRule();
  
      /** Sets {@link #converterRule()}. */
      Config withConverterRule(ConverterRule converterRule);
    }
  }
  