comphead commented on code in PR #26544:
URL: https://github.com/apache/datafusion/pull/26544#discussion_r4338795873
##########
datafusion/optimizer/src/decorrelate.rs:
##########
@@ -505,6 +505,12 @@ impl TreeNodeRewriter for PullUpCorrelatedExpr {
if !is_distinct {
self.can_pull_up = self.can_pull_up &&
self.can_pull_over_aggregation;
}
+ // A pulled up scalar aggregate below gives no row for
unmatched
+ // outer rows, so this aggregate would see an empty input.
+ // See https://github.com/apache/datafusion/issues/26508
+ if self.pulled_up_scalar_agg {
+ self.can_pull_up = false;
+ }
Review Comment:
The check moved to the top of the `Aggregate` branch. It now sets
`can_pull_up = false` and returns early with `TreeNodeRecursion::Stop`, which
fixes the schema error jayzhan211 found (details in the top-level comment).
That leaves no second update of `can_pull_up` to fold. The check is still
outside the `is_distinct` block. I also added the doc comment on
`pulled_up_scalar_agg`.
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