AngersZhuuuu commented on a change in pull request #27861:
[SPARK-30707][SQL]Window function set partitionSpec as order spec when
orderSpec is empty
URL: https://github.com/apache/spark/pull/27861#discussion_r390793409
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/parser/AstBuilder.scala
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@@ -1691,7 +1691,15 @@ class AstBuilder(conf: SQLConf) extends
SqlBaseBaseVisitor[AnyRef] with Logging
override def visitWindowDef(ctx: WindowDefContext): WindowSpecDefinition =
withOrigin(ctx) {
// CLUSTER BY ... | PARTITION BY ... ORDER BY ...
val partition = ctx.partition.asScala.map(expression)
- val order = ctx.sortItem.asScala.map(visitSortItem)
+ val order = if (ctx.sortItem.asScala.nonEmpty) {
+ ctx.sortItem.asScala.map(visitSortItem)
+ } else {
+ // Same default behaviors like hive, when order spec is null
Review comment:
> From the ANSI SQL spec: `If WD has no window ordering clause, then the
window ordering is implementation-dependent, and all rows are peers.`
>
> I don't think this is a bug fix but rather a new feature. We need to
justify it: what's the behavior of other popular SQL systems like presto,
snowflake, redshift, etc.? And what's the benefit for end users?
I will check other SQL system later.
In our production, one benefit is we can migrate hive sql to spark sql
smother and don't need to rewrite sql one by one
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