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[SPARK-49000][SQL][FOLLOWUP] Improve code style and update comments #47565

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[SPARK-49000][SQL][FOLLOWUP] Improve code style and update comments #47565

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f1029aa
Small fixes
uros-db Aug 1, 2024
4de8c15
Update comment
uros-db Aug 1, 2024
9fb6429
Update RewriteDistinctAggregates.scala
uros-db Aug 1, 2024
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15 changes: 8 additions & 7 deletions ...st/src/main/scala/org/apache/spark/sql/catalyst/optimizer/RewriteDistinctAggregates.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -198,13 +198,15 @@ import org.apache.spark.util.collection.Utils
*/
object RewriteDistinctAggregates extends Rule[LogicalPlan] {
private def mustRewrite(
aggregateExpressions: Seq[AggregateExpression],
distinctAggs: Seq[AggregateExpression],
groupingExpressions: Seq[Expression]): Boolean = {
// If there are any AggregateExpressions with filter, we need to rewrite the query.
// Also, if there are no grouping expressions and all aggregate expressions are foldable,
// we need to rewrite the query, e.g. SELECT COUNT(DISTINCT 1).
aggregateExpressions.exists(_.filter.isDefined) || (groupingExpressions.isEmpty &&
aggregateExpressions.exists(_.aggregateFunction.children.forall(_.foldable)))
// If there are any distinct AggregateExpressions with filter, we need to rewrite the query.
// Also, if there are no grouping expressions and all distinct aggregate expressions are
// foldable, we need to rewrite the query, e.g. SELECT COUNT(DISTINCT 1). Without this case,
// non-grouping aggregation queries with distinct aggregate expressions will be incorrectly
// handled by the aggregation strategy, causing wrong results when working with empty tables.
distinctAggs.exists(_.filter.isDefined) || (groupingExpressions.isEmpty &&
distinctAggs.exists(_.aggregateFunction.children.forall(_.foldable)))
}

private def mayNeedtoRewrite(a: Aggregate): Boolean = {
Expand All @@ -213,7 +215,6 @@ object RewriteDistinctAggregates extends Rule[LogicalPlan] {
// We need at least two distinct aggregates or the single distinct aggregate group exists filter
// clause for this rule because aggregation strategy can handle a single distinct aggregate
// group without filter clause.
// This check can produce false-positives, e.g., SUM(DISTINCT a) & COUNT(DISTINCT a).
distinctAggs.size > 1 || mustRewrite(distinctAggs, a.groupingExpressions)
}

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