mbutrovich commented on code in PR #1424:
URL: https://github.com/apache/datafusion-comet/pull/1424#discussion_r1963816392
##########
spark/src/main/scala/org/apache/comet/rules/RewriteJoin.scala:
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@@ -67,4 +78,21 @@ object RewriteJoin extends JoinSelectionHelper {
}
case _ => plan
}
+
+ def getOptimalBuildSide(join: Join): BuildSide = {
+ val leftSize = join.left.stats.sizeInBytes
+ val rightSize = join.right.stats.sizeInBytes
+ val leftRowCount = join.left.stats.rowCount
+ val rightRowCount = join.right.stats.rowCount
+ if (leftSize == rightSize && rightRowCount.isDefined &&
leftRowCount.isDefined) {
+ if (rightRowCount.get <= leftRowCount.get) {
Review Comment:
Do we have any sort of cardinality stats (possibly with some catalog
implementations)? I'm envisioning a scenario where the right table has fewer
rows but much higher cardinality so the resulting hash table is bigger.
Maybe a follow-up issue makes sense to add more heuristics (if we can even
get them) to this choice.
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