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.Calc;
  import org.apache.calcite.rex.RexOver;
  import org.apache.calcite.rex.RexProgram;
  import org.apache.calcite.rex.RexProgramBuilder;
  import org.apache.calcite.tools.RelBuilderFactory;
  
  import org.immutables.value.Value;
  
  /**
   * Planner rule that merges a
   * {@link org.apache.calcite.rel.core.Calc} onto a
   * {@link org.apache.calcite.rel.core.Calc}.
   *
   * <p>The resulting {@link org.apache.calcite.rel.core.Calc} has the
   * same project list as the upper
   * {@link org.apache.calcite.rel.core.Calc}, but expressed in terms of
   * the lower {@link org.apache.calcite.rel.core.Calc}'s inputs.
   *
   * @see CoreRules#CALC_MERGE
   */
  @Value.Enclosing
  public class CalcMergeRule extends RelRule<CalcMergeRule.Config>
      implements TransformationRule {
  
    /** Creates a CalcMergeRule. */
    protected CalcMergeRule(Config config) {
      super(config);
    }
  
    @Deprecated // to be removed before 2.0
    public CalcMergeRule(RelBuilderFactory relBuilderFactory) {
      this(Config.DEFAULT.withRelBuilderFactory(relBuilderFactory)
          .as(Config.class));
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public void onMatch(RelOptRuleCall call) {
      final Calc topCalc = call.rel(0);
      final Calc bottomCalc = call.rel(1);
  
      // Don't merge a calc which contains windowed aggregates onto a
      // calc. That would effectively be pushing a windowed aggregate down
      // through a filter.
      RexProgram topProgram = topCalc.getProgram();
      if (RexOver.containsOver(topProgram)) {
        return;
      }
  
      // Merge the programs together.
  
      RexProgram mergedProgram =
          RexProgramBuilder.mergePrograms(
              topCalc.getProgram(),
              bottomCalc.getProgram(),
              topCalc.getCluster().getRexBuilder());
      assert mergedProgram.getOutputRowType()
          == topProgram.getOutputRowType();
      final Calc newCalc =
          topCalc.copy(
              topCalc.getTraitSet(),
              bottomCalc.getInput(),
              mergedProgram);
  
      if (newCalc.getDigest().equals(bottomCalc.getDigest())
          && newCalc.getRowType().equals(bottomCalc.getRowType())) {
        // newCalc is equivalent to bottomCalc, which means that topCalc
        // must be trivial. Take it out of the game.
        call.getPlanner().prune(topCalc);
      }
  
      call.transformTo(newCalc);
    }
  
    /** Rule configuration. */
    @Value.Immutable
    public interface Config extends RelRule.Config {
      Config DEFAULT = ImmutableCalcMergeRule.Config.of()
          .withOperandSupplier(b0 ->
              b0.operand(Calc.class).oneInput(b1 ->
                  b1.operand(Calc.class).anyInputs()))
          .as(Config.class);
  
      @Override default CalcMergeRule toRule() {
        return new CalcMergeRule(this);
      }
    }
  }
  