iwanttobepowerful commented on code in PR #4997:
URL: https://github.com/apache/calcite/pull/4997#discussion_r3369181868
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core/src/main/java/org/apache/calcite/sql2rel/RelDecorrelator.java:
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@@ -2487,6 +2502,57 @@ private DecorrelateRexShuttle(RelNode currentRel,
return fieldAccess;
}
+ /**
+ * Window operators are decorrelated similarly to aggregates. A correlated
+ * window expression is evaluated once per outer-row binding before
+ * decorrelation; after decorrelation, outer references are represented as
+ * ordinary input fields. Therefore, add those fields to the window
partition
+ * keys so that the window function is still evaluated independently for
+ * each outer-row binding.
+ *
+ * <p>Implementation based on: Improving Unnesting of Complex Queries
+ *
+ * <p>3.3 Unnesting Rules
+ *
(https://dl.gi.de/server/api/core/bitstreams/c1918e8c-6a87-4da2-930a-bfed289f2388/content)
+ */
+ @Override public RexNode visitOver(RexOver over) {
Review Comment:
the two fixes are related but apply to different shuttles. This PR updates
`visitOver` in `DecorrelateRexShuttle`, while #4998 updates `visitOver` in
`RemoveCorrelationRexShuttle`.
I also verified that if `RemoveCorrelationForScalarAggregateRule` is
disabled in `removeCorrelationViaRule()`, the #4998 fix does not seem to be
needed. So #4998 appears to address the rule-based decorrelation path, whereas
this PR addresses the `DecorrelateRexShuttle` path.
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