thomasrebele commented on code in PR #4646:
URL: https://github.com/apache/calcite/pull/4646#discussion_r2559204828
##########
core/src/main/java/org/apache/calcite/rex/RexSimplify.java:
##########
@@ -1153,16 +1153,15 @@ private RexNode simplifyIs(RexCall call, RexUnknownAs
unknownAs) {
return rexBuilder.makeLiteral(true);
}
if (RexUtil.isLosslessCast(a)) {
- if (!a.getType().isNullable()) {
- return rexBuilder.makeLiteral(true);
- }
- return rexBuilder.makeCall(SqlStdOperatorTable.IS_NOT_NULL,
RexUtil.removeCast(a));
+ a = RexUtil.removeCast(a);
+ // to keep this simplification, we must return IS NOT NULL(a),
+ // even if we cannot do anything else
}
if (predicates.pulledUpPredicates.contains(a)) {
return rexBuilder.makeLiteral(true);
}
if (hasCustomNullabilityRules(a.getKind())) {
- return null;
+ return rexBuilder.makeCall(SqlStdOperatorTable.IS_NOT_NULL, a);
Review Comment:
I've added [a
comment](https://github.com/apache/calcite/pull/4646/files/1fc0329b966dcd82aaeb52bd04a09ae8781000be#diff-047d75692a99d7b5c0d9b1aefc04549ec766e0a45a895b2e04a2cfa0fa6b073eR1157-R1158)
why we need to return `IS NOT NULL(a)`. If we return just `null`, we would not
remove the superfluous lossless cast.
I'll add a check whether a has changed.
Thank you for pointing out that there exist a version of makeCall that
allows to specify the source position. The [existing
fallback](https://github.com/thomasrebele/calcite/blob/1fc0329b966dcd82aaeb52bd04a09ae8781000be/core/src/main/java/org/apache/calcite/rex/RexSimplify.java#L1138-L1140)
has no source position either. Reading
[CALCITE-6071](https://issues.apache.org/jira/browse/CALCITE-6071), it seems
that only calls that may throw should be annotated with the source position. As
`IS NULL` / `IS NOT NULL` don't throw themselves, they would not need the
source position.
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