dengziming commented on code in PR #51686:
URL: https://github.com/apache/spark/pull/51686#discussion_r2242856210
##########
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/v2/V2ScanRelationPushDown.scala:
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@@ -226,10 +195,54 @@ object V2ScanRelationPushDown extends Rule[LogicalPlan]
with PredicateHelper {
}
}
- def generateJoinOutputAlias(name: String): String =
- s"${name}_${java.util.UUID.randomUUID().toString.replace("-", "_")}"
+ private def generateColumnAliasesForDuplicatedName(
+ leftSideRequiredColumnNames: Array[String],
+ rightSideRequiredColumnNames: Array[String]
+ ): (Array[SupportsPushDownJoin.ColumnWithAlias],
+ Array[SupportsPushDownJoin.ColumnWithAlias]) = {
+ // Count occurrences of each column name across both sides to identify
duplicates.
+ val allRequiredColumnNames = leftSideRequiredColumnNames ++
rightSideRequiredColumnNames
+ val allNameCounts: Map[String, Int] =
+ allRequiredColumnNames.groupBy(identity).view.mapValues(_.size).toMap
Review Comment:
I don't think it's necessary after some investigation, if our sql is `select
* from a(id,sid) join b(id,Sid)`, we can have 2 versions of SQL pushdown to
database:
1. `select id, sid, id_1, Sid from (select id, sid from a) join (select id
as id_1, Sid from b)`
2. `select id, sid, id_1, sid_1 from (select id, sid from a) join (select id
as id_1, Sid as sid_1 from b)`
I added this to my test case to show version 1 also can work, and version 2
doesn't make the sql clearer.
Is it possible we will meet `AMBIGUOUS_REFERENCE` in version 1?
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