PetarVasiljevic-DB commented on code in PR #50921:
URL: https://github.com/apache/spark/pull/50921#discussion_r2206670819
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sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/V2ScanRelationPushDown.scala:
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@@ -98,6 +100,146 @@ object V2ScanRelationPushDown extends Rule[LogicalPlan]
with PredicateHelper {
filterCondition.map(Filter(_, sHolder)).getOrElse(sHolder)
}
+ def pushDownJoin(plan: LogicalPlan): LogicalPlan = plan.transformUp {
+ // Join can be attempted to be pushed down only if left and right side of
join are
+ // compatible (same data source, for example). Also, another requirement
is that if
+ // there are projections between Join and ScanBuilderHolder, these
projections need to be
+ // AttributeReferences. We could probably support Alias as well, but this
should be on
+ // TODO list.
+ // Alias can exist between Join and sHolder node because the query below
is not valid:
+ // SELECT * FROM
+ // (SELECT * FROM tbl t1 JOIN tbl2 t2) p
+ // JOIN
+ // (SELECT * FROM tbl t3 JOIN tbl3 t4) q
+ // ON p.t1.col = q.t3.col (this is not possible)
Review Comment:
If `col` is part of both the tables t1 and t2, then you can't reference it
with `p.col`.
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