andylam-db commented on code in PR #43341:
URL: https://github.com/apache/spark/pull/43341#discussion_r1357456302
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sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/subquery.scala:
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@@ -360,8 +360,40 @@ object PullupCorrelatedPredicates extends
Rule[LogicalPlan] with PredicateHelper
plan.transformExpressionsWithPruning(_.containsPattern(PLAN_EXPRESSION)) {
case ScalarSubquery(sub, children, exprId, conditions, hint,
mayHaveCountBugOld)
if children.nonEmpty =>
- val (newPlan, newCond) = decorrelate(sub, plan)
- val mayHaveCountBug = if (mayHaveCountBugOld.isEmpty) {
+
+ def mayHaveCountBugAgg(a: Aggregate): Boolean = {
+ a.groupingExpressions.isEmpty &&
a.aggregateExpressions.exists(_.exists {
+ case a: AggregateExpression =>
a.aggregateFunction.defaultResult.isDefined
+ case _ => false
+ })
+ }
+
+ // The below logic controls handling count bug for scalar subqueries in
+ // [[DecorrelateInnerQuery]], and if we don't handle it here, we
handle it in
+ // [[RewriteCorrelatedScalarSubquery#constructLeftJoins]]. Note that
handling it in
+ // [[DecorrelateInnerQuery]] is always correct, and turning it off to
handle it in
+ // constructLeftJoins is an optimization, so that additional,
redundant left outer joins are
+ // not introduced.
+ val handleCountBugInDecorrelate = !conf.getConf(
+ SQLConf.LEGACY_SCALAR_SUBQUERY_COUNT_BUG_HANDLING) && !(sub match {
+ // Handle count bug only if there exists lower level Aggs with count
bugs. It does not
+ // matter if the top level agg is count bug vulnerable or not,
because:
+ // 1. If the top level agg is count bug vulnerable, it can be
handled in
+ // constructLeftJoins, unless there are lower aggs that are count
bug vulnerable.
+ // E.g. COUNT(COUNT + COUNT)
+ // 2. If the top level agg is not count bug vulnerable, it can be
count bug vulnerable if
+ // there are lower aggs that are count bug vulnerable. E.g.
SUM(COUNT)
+ case agg: Aggregate => !agg.child.exists {
+ case lowerAgg: Aggregate => mayHaveCountBugAgg(lowerAgg)
+ case _ => false
+ }
+ case _ => false
+ })
+ val (newPlan, newCond) = decorrelate(sub, plan,
handleCountBugInDecorrelate)
+ val mayHaveCountBug = if (handleCountBugInDecorrelate) {
+ // Count bug was already handled in the above decorrelate function
call.
+ false
+ } else if (mayHaveCountBugOld.isEmpty) {
Review Comment:
If the plan has already been decorrelated and count bugs handled in
`decorrelate()` above, then we can't set `mayHaveCountBug` parameter to be
true. This is because if we set it as true based on the pre-rewrite plan (which
is what's happening now), running `splitSubquery()` in `constructLeftJoins`
will fail because it encounters left outer joins (invalid operators).
Edit: but yeah, from the failing build it appears like i'm facing some
issues with idempotency.
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