[CALCITE-3630] Improve ReduceExpressionsRule

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.21.0
• Fix Version/s: 1.22.0
• Component/s: core
• Labels: pull-request-available
• Assignee: Chunwei Lei
• Reporter: Chunwei Lei
• Created: 25/Dec/19 04:00
• Updated: 27/Dec/21 20:46
• Resolved: 27/Dec/19 07:39

Description

In FilterReduceExpressionsRule, if the expression is a IS [NOT] NULL on a non-nullable column, then we can either remove the filter or replace it with an Empty(namely reduceNotNullableFilter). In such a case, we can set importance to 0 to reduce search space.

 

// code placeholder
  private void reduceNotNullableFilter(
      RelOptRuleCall call,
      Filter filter,
      RexNode rexNode,
      boolean reverse) {
    // If the expression is a IS [NOT] NULL on a non-nullable
    // column, then we can either remove the filter or replace
    // it with an Empty.
    boolean alwaysTrue;
    switch (rexNode.getKind()) {
    case IS_NULL:
    case IS_UNKNOWN:
      alwaysTrue = false;
      break;
    case IS_NOT_NULL:
      alwaysTrue = true;
      break;
    default:
      return;
    }
    if (reverse) {
      alwaysTrue = !alwaysTrue;
    }
    RexNode operand = ((RexCall) rexNode).getOperands().get(0);
    if (operand instanceof RexInputRef) {
      RexInputRef inputRef = (RexInputRef) operand;
      if (!inputRef.getType().isNullable()) {
        if (alwaysTrue) {
          call.transformTo(filter.getInput());
        } else {
          call.transformTo(createEmptyRelOrEquivalent(call, filter));
        }
      }
    }
  }
}

 

Issue Links

• is related to: CALCITE-4964 Reduce recursion when push predicate into CASE
• links to: GitHub Pull Request #1686