andygrove commented on code in PR #1424:
URL: https://github.com/apache/datafusion-comet/pull/1424#discussion_r1964310525
##########
spark/src/main/scala/org/apache/comet/rules/RewriteJoin.scala:
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@@ -67,4 +83,21 @@ 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) {
Review Comment:
I suppose it depends on the goal for choosing the build-side. Do we want to
limit the amount of data that needs to be loaded into the hash map or limit the
number of rows?
The article you linked is for reordering nested joins, so row count would
likely be more critical for that scenario.
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