cloud-fan commented on a change in pull request #27187: [SPARK-30497][SQL]
migrate DESCRIBE TABLE to the new framework
URL: https://github.com/apache/spark/pull/27187#discussion_r366233395
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File path:
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala
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@@ -759,6 +759,8 @@ class Analyzer(
u.failAnalysis(s"${ident.quoted} is a temp view not table.")
}
u
+ case u @ UnresolvedTableOrView(ident) =>
+ lookupTempView(ident).getOrElse(u)
Review comment:
some commands don't need to scan the table/view (like DESCRIBE). If we use
`UnresolvedRelation`, then we will end up with `DataSourceV2ScanRelation`,
which creates `Scan` from `Table` and is not necessary.
Another problem is view. `UnresolvedRelation` can be resolved to `View`, and
then get removed at the beginning of optimizer.
I'll think of how to overcome these issues and reuse `UnresolvedRelation`.
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