gatorsmile commented on a change in pull request #24286: [SPARK-27351][SQL]
Wrong outputRows estimation after AggregateEstimation with only null value
column
URL: https://github.com/apache/spark/pull/24286#discussion_r277223008
##########
File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/statsEstimation/AggregateEstimation.scala
##########
@@ -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 distinctCount = columnStat.distinctCount.get
+ val distinctValue: BigInt = if (distinctCount == 0 &&
columnStat.nullCount.get > 0) {
+ 1
+ } else {
+ distinctCount
Review comment:
If the nullCount is not empty, the value should be `distinctCount + 1`,
right?
@pengbo @dongjoon-hyun
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