comphead commented on code in PR #1424:
URL: https://github.com/apache/datafusion-comet/pull/1424#discussion_r1964288717
##########
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:
maybe I missing something? `leftSize == rightSize` condition looks very
unlikely so by the logic it would never consider rowCounts here and fallback to
sizes.
We can perhaps use something like
https://docs.pingcap.com/tidb/stable/join-reorder#example-the-greedy-algorithm-of-join-reorder
and if rowCounts are not available fallback to sizes
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