srowen commented on a change in pull request #24286: [SPARK-27351][SQL] Wrong
outputRows estimation after AggregateEstimation wit…
URL: https://github.com/apache/spark/pull/24286#discussion_r275136453
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/statsEstimation/AggregateEstimation.scala
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@@ -39,8 +39,16 @@ object AggregateEstimation {
// Multiply distinct counts of group-by columns. This is an upper bound,
which assumes
// the data contains all combinations of distinct values of group-by
columns.
var outputRows: BigInt = agg.groupingExpressions.foldLeft(BigInt(1))(
- (res, expr) => res *
-
childStats.attributeStats(expr.asInstanceOf[Attribute]).distinctCount.get)
+ (res, expr) => {
+ val columnStat =
childStats.attributeStats(expr.asInstanceOf[Attribute])
+ val distinctValue: BigInt = if (columnStat.distinctCount.get == 0 &&
Review comment:
I'm slightly concerned about performance here. Can you save the value of
distinctCount.get so it isn't accessed twice, or is it not actually recomputed
twice as-is?
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