andygrove commented on code in PR #1424:
URL: https://github.com/apache/datafusion-comet/pull/1424#discussion_r1963989909
##########
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:
With AQE enabled, we have rowCount and sizeInBytes available for completed
query stages. We could extend the logic here to also look at
`LogicalRelation.sizeInBytes` if the AQE stats are not available (this could be
the case for the first join in a query).
@mbutrovich also suggested that we take into account the size of the data
that will go into the build-side hash table i.e. consider which columns are
uses in the join.
I think we can experiment more with this. I will file an issue to track this.
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