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.RelNode;
  import org.apache.calcite.rel.core.Join;
  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.sql.type.SqlTypeName;
  import org.apache.calcite.tools.RelBuilder;
  
  import org.immutables.value.Value;
  
  /**
   * Planner rule that replaces {@code IS NOT DISTINCT FROM}
   * in a {@link Join} condition with logically equivalent operations.
   *
   * @see SqlStdOperatorTable#IS_NOT_DISTINCT_FROM
   * @see RelBuilder#isNotDistinctFrom
   */
  @Value.Enclosing
  public final class JoinConditionExpandIsNotDistinctFromRule
      extends RelRule<JoinConditionExpandIsNotDistinctFromRule.Config>
      implements TransformationRule {
  
    /** Creates a JoinConditionExpandIsNotDistinctFromRule. */
    JoinConditionExpandIsNotDistinctFromRule(Config config) {
      super(config);
    }
  
    //~ Methods ----------------------------------------------------------------
  
    @Override public void onMatch(RelOptRuleCall call) {
      Join join = call.rel(0);
      RexNode oldJoinCond = join.getCondition();
  
      RexCall found =
          RexUtil.findOperatorCall(SqlStdOperatorTable.IS_NOT_DISTINCT_FROM,
          oldJoinCond);
  
      if (found == null) {
        // no longer contains isNotDistinctFromOperator
        return;
      }
  
      for (RexNode op : found.getOperands()) {
        if (op.getType().getSqlTypeName() == SqlTypeName.MAP) {
          // map type cannot be compared
          return;
        }
      }
  
      RemoveIsNotDistinctFromRexShuttle rewriteShuttle =
          new RemoveIsNotDistinctFromRexShuttle(
              join.getCluster().getRexBuilder());
  
      RelNode newJoin = join.accept(rewriteShuttle);
      assert newJoin instanceof Join;
      if (((Join) newJoin).getCondition().equals(join.getCondition())) {
        return;
      }
      call.transformTo(newJoin);
    }
  
    //~ Inner Classes ----------------------------------------------------------
  
    /** The RexShuttle use for converting 'x IS NOT DISTINCT FROM y' to
     * '(COALESCE(x, {zero}) = COALESCE(y, {zero}))
     * AND ((x IS NULL) = (y IS NULL))'. */
    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;
  
          RexNode operand0 = tmpCall.operands.get(0);
          RexNode operand1 = tmpCall.operands.get(1);
  
          RexNode operand0Zero = rexBuilder.makeZeroRexNode(operand0.getType());
          RexNode operand1Zero = rexBuilder.makeZeroRexNode(operand1.getType());
  
          RexNode coalesceCondition =
              rexBuilder.makeCall(SqlStdOperatorTable.EQUALS,
              rexBuilder.makeCall(SqlStdOperatorTable.COALESCE,
                  operand0, operand0Zero),
              rexBuilder.makeCall(SqlStdOperatorTable.COALESCE,
                  operand1, operand1Zero));
  
          RexNode isNullCondition =
              rexBuilder.makeCall(SqlStdOperatorTable.EQUALS,
              rexBuilder.makeCall(SqlStdOperatorTable.IS_NULL, operand0),
              rexBuilder.makeCall(SqlStdOperatorTable.IS_NULL, operand1));
  
          newCall =
              rexBuilder.makeCall(SqlStdOperatorTable.AND,
                  coalesceCondition, isNullCondition);
        }
        return newCall;
      }
    }
  
    /** Rule configuration. */
    @Value.Immutable
    public interface Config extends RelRule.Config {
      Config DEFAULT = ImmutableJoinConditionExpandIsNotDistinctFromRule.Config.of()
          .withOperandSupplier(b -> b.operand(Join.class).anyInputs());
  
      @Override default JoinConditionExpandIsNotDistinctFromRule toRule() {
        return new JoinConditionExpandIsNotDistinctFromRule(this);
      }
    }
  }
  