dongjoon-hyun commented on a change in pull request #25029: [SPARK-28228][SQL] 
Fix substitution order of nested WITH clauses
URL: https://github.com/apache/spark/pull/25029#discussion_r300752978
 
 

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 File path: docs/sql-migration-guide-upgrade.md
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 @@ -147,6 +147,8 @@ license: |
 
   - Since Spark 3.0, if files or subdirectories disappear during recursive 
directory listing (i.e. they appear in an intermediate listing but then cannot 
be read or listed during later phases of the recursive directory listing, due 
to either concurrent file deletions or object store consistency issues) then 
the listing will fail with an exception unless 
`spark.sql.files.ignoreMissingFiles` is `true` (default `false`). In previous 
versions, these missing files or subdirectories would be ignored. Note that 
this change of behavior only applies during initial table file listing (or 
during `REFRESH TABLE`), not during query execution: the net change is that 
`spark.sql.files.ignoreMissingFiles` is now obeyed during table file listing / 
query planning, not only at query execution time.
 
+  - Since Spark 3.0, substitution order of nested WITH clauses is changed and 
an inner CTE definition takes precedence over an outer. The previous behaviour 
can be restored by setting `spark.sql.legacy.cte.substitution.enabled` to 
`true`.
 
 Review comment:
   Thanks.

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