NobiGo commented on code in PR #4022:
URL: https://github.com/apache/calcite/pull/4022#discussion_r1825678979
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core/src/main/java/org/apache/calcite/rel/rules/SubQueryRemoveRule.java:
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@@ -170,6 +170,13 @@ private static RexNode rewriteCollection(RexSubQuery e,
*/
private static RexNode rewriteSome(RexSubQuery e, Set<CorrelationId>
variablesSet,
RelBuilder builder, int subQueryIndex) {
+ // If the sub-query is guaranteed to return 0 row, just return
+ // FALSE.
+ final RelMetadataQuery mq = e.rel.getCluster().getMetadataQuery();
+ final Double maxRowCount = mq.getMaxRowCount(e.rel);
+ if (maxRowCount != null && maxRowCount < 1D) {
Review Comment:
> I have the same concern as @dssysolyatin. Could we instead check whether
it is an instance of `Values` and then call `Values.isEmpty`? (Which is how
`PruneEmptyRules` works.)
I think we can't. Now we apply `SubQueryRemoveRule` before
`PruneEmptyRules`. so the sub-query is not a VALUES.
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