juntaozhang commented on code in PR #4338:
URL: https://github.com/apache/calcite/pull/4338#discussion_r2062586723
##########
core/src/main/java/org/apache/calcite/rel/rules/SortJoinTransposeRule.java:
##########
@@ -116,13 +121,26 @@ public SortJoinTransposeRule(Class<? extends Sort>
sortClass,
mq, join.getLeft(), joinInfo.leftSet())) {
return false;
}
+ if (alreadyPushedDown(join.getRight())) {
+ return false;
+ }
} else {
return false;
}
return true;
}
+ // Returns true if the sort has already been pushed down
+ private boolean alreadyPushedDown(RelNode rel) {
Review Comment:
I'm very glad that you can review this PR. Your two questions seem to be
answered in
`testSortJoinTranspose6`[CALCITE-1507](https://issues.apache.org/jira/browse/CALCITE-1507),
it explains when pushing down has no impact. This PR fix if the pushdown
succeeds, under certain rules, it could enter a loop of transpositions, leading
to a stack overflow.
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