hvanhovell opened a new pull request #27562: [SPARK-30811][SQL][BRANCH-2.4] CTE should not cause stack overflow when it refers to non-existent table with same name URL: https://github.com/apache/spark/pull/27562 ### Why are the changes needed? A query with Common Table Expressions can cause a stack overflow when it contains a CTE that refers a non-existing table with the same name. The name of the table need to have a database qualifier. This is caused by a couple of things: - `CTESubstitution` runs analysis on the CTE, but this does not throw an exception because the table has a database qualifier. The reason is that we don't fail is because we re-attempt to resolve the relation in a later rule; - `CTESubstitution` replace logic does not check if the table it is replacing has a database, it shouldn't replace the relation if it does. So now we will happily replace `nonexist.t` with `t`; - `CTESubstitution` transforms down, this means it will keep replacing t with itself, creating an infinite recursion. This PR fixes this by checking whether the relation name does not have a database, and it also reverses the transformation order. ### Does this PR introduce any user-facing change? No ### How was this patch tested? Added regression test to `DataFrameSuite`.
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