[jira] [Commented] (CALCITE-3630) Improve ReduceExpressionsRule

["Chunwei Lei (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CALCITE-3630?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17003436#comment-17003436 ] 

Chunwei Lei commented on CALCITE-3630:
--------------------------------------

Though we might recommend users not to use {{setImportance(0)}}, IMO, if we already do it in this rule[1], it makes sense to do it to be consistent.

[1] [https://github.com/apache/calcite/blob/master/core/src/main/java/org/apache/calcite/rel/rules/ReduceExpressionsRule.java#L216]

> Improve ReduceExpressionsRule
> -----------------------------
>
>                 Key: CALCITE-3630
>                 URL: https://issues.apache.org/jira/browse/CALCITE-3630
>             Project: Calcite
>          Issue Type: Bug
>          Components: core
>    Affects Versions: 1.21.0
>            Reporter: Chunwei Lei
>            Assignee: Chunwei Lei
>            Priority: Major
>              Labels: pull-request-available
>          Time Spent: 0.5h
>  Remaining Estimate: 0h
>
> 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:java}
> // 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));
>         }
>       }
>     }
>   }
> }
> {code}
>  



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