ulysses-you commented on a change in pull request #30974:
URL: https://github.com/apache/spark/pull/30974#discussion_r551157649
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File path: sql/core/src/main/scala/org/apache/spark/sql/Column.scala
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@@ -200,6 +203,7 @@ class Column(val expr: Expression) extends Logging {
// Wait until the struct is resolved. This will generate a nicer looking
alias.
case struct: CreateNamedStruct => UnresolvedAlias(struct)
+ case expr: Expression if existsUnresolvedExtractValue(expr) =>
UnresolvedAlias(expr)
Review comment:
The reason why not check other `Expression` is `UnresolvedAlias` will
introduce `CAST` to assgin name duing analysis if exists type cast implicitly.
As I said above
> Before that df.selectExpr("id1 == null").schema.head.name is (id1 = NULL),
after that it changed to (id1 = CAST(NULL AS INT)).
Narrow to checked `UnresolvedExtractValue` is just a tradeoff.
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