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.RelOptUtil;
  import org.apache.calcite.plan.RelRule;
  import org.apache.calcite.rel.RelNode;
  import org.apache.calcite.rel.core.Filter;
  import org.apache.calcite.rex.RexBuilder;
  import org.apache.calcite.rex.RexCall;
  import org.apache.calcite.rex.RexNode;
  import org.apache.calcite.rex.RexShuttle;
  import org.apache.calcite.rex.RexUtil;
  import org.apache.calcite.sql.fun.SqlStdOperatorTable;
  import org.apache.calcite.tools.RelBuilder;
  import org.apache.calcite.tools.RelBuilderFactory;
  
  import org.immutables.value.Value;
  
  /**
   * Planner rule that replaces {@code IS NOT DISTINCT FROM}
   * in a {@link Filter} with logically equivalent operations.
   *
   * @see org.apache.calcite.sql.fun.SqlStdOperatorTable#IS_NOT_DISTINCT_FROM
   * @see CoreRules#FILTER_EXPAND_IS_NOT_DISTINCT_FROM
   * @see RelBuilder#isDistinctFrom
   * @see RelBuilder#isNotDistinctFrom
   */
  @Value.Enclosing
  public final class FilterRemoveIsNotDistinctFromRule
      extends RelRule<FilterRemoveIsNotDistinctFromRule.Config>
      implements TransformationRule {
  
    /** Creates a FilterRemoveIsNotDistinctFromRule. */
    FilterRemoveIsNotDistinctFromRule(Config config) {
      super(config);
    }
  
    @Deprecated // to be removed before 2.0
    public FilterRemoveIsNotDistinctFromRule(
        RelBuilderFactory relBuilderFactory) {
      this(Config.DEFAULT.withRelBuilderFactory(relBuilderFactory)
          .as(Config.class));
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public void onMatch(RelOptRuleCall call) {
      Filter oldFilter = call.rel(0);
      RexNode oldFilterCond = oldFilter.getCondition();
  
      if (RexUtil.findOperatorCall(
          SqlStdOperatorTable.IS_NOT_DISTINCT_FROM,
          oldFilterCond)
          == null) {
        // no longer contains isNotDistinctFromOperator
        return;
      }
  
      // Now replace all the "a isNotDistinctFrom b"
      // with the RexNode given by RelOptUtil.isDistinctFrom() method
  
      RemoveIsNotDistinctFromRexShuttle rewriteShuttle =
          new RemoveIsNotDistinctFromRexShuttle(
              oldFilter.getCluster().getRexBuilder());
  
      final RelBuilder relBuilder = call.builder();
      final RelNode newFilterRel = relBuilder
          .push(oldFilter.getInput())
          .filter(oldFilterCond.accept(rewriteShuttle))
          .build();
  
      call.transformTo(newFilterRel);
    }
  
    //~ Inner Classes ----------------------------------------------------------
  
    /** Shuttle that removes 'x IS NOT DISTINCT FROM y' and converts it
     * to 'CASE WHEN x IS NULL THEN y IS NULL WHEN y IS NULL THEN x IS
     * NULL ELSE x = y END'. */
    private static class RemoveIsNotDistinctFromRexShuttle extends RexShuttle {
      final RexBuilder rexBuilder;
  
      RemoveIsNotDistinctFromRexShuttle(
          RexBuilder rexBuilder) {
        this.rexBuilder = rexBuilder;
      }
  
      @Override public RexNode visitCall(RexCall call) {
        RexNode newCall = super.visitCall(call);
  
        if (call.getOperator()
            == SqlStdOperatorTable.IS_NOT_DISTINCT_FROM) {
          RexCall tmpCall = (RexCall) newCall;
          newCall =
              RelOptUtil.isDistinctFrom(
                  rexBuilder,
                  tmpCall.operands.get(0),
                  tmpCall.operands.get(1),
                  true);
        }
        return newCall;
      }
    }
  
    /** Rule configuration. */
    @Value.Immutable
    public interface Config extends RelRule.Config {
      Config DEFAULT = ImmutableFilterRemoveIsNotDistinctFromRule.Config.of()
          .withOperandSupplier(b -> b.operand(Filter.class).anyInputs());
  
      @Override default FilterRemoveIsNotDistinctFromRule toRule() {
        return new FilterRemoveIsNotDistinctFromRule(this);
      }
    }
  }
  