Implement nested recursive CTEs #18956
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It gives a name (the table name) to each WorkTable. This way WorkTableExec can recognize its own WorkTable Note that it doesn't allow multiple occurrences of the same CTE name: it's not possible to implement things like "join with itself" correctly with only the work table.
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martin-g
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Nov 27, 2025
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LGTM! 👍🏻
One question: Should name shadowing in nested CTEs be supported ?
Some databases (e.g. Postgres) support it, others - don't.
If it is supported then it would be good to add a test case.
If it is not then it would be good to document it somewhere.
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@martin-g Thank you!
This is a good point. Thank you! It's not supported yet, might be nice to support it. I have added a test in 0db8728 Currently it raises "Error during planning: WITH query name "outer_cte" specified more than once" which sounds like a fair error message. |
Jefffrey
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It gives a name (the table name) to each
WorkTable. This wayWorkTableExeccan recognize its ownWorkTableNote that it doesn't allow multiple occurrences of the same CTE name: it's not possible to implement things like "join with itself" correctly with only the work table.
Which issue does this PR close?
Rationale for this change
Support nested recursive CTEs without co-recursion. This is useful to e.g. implement SPARQL or other graph query languages.
What changes are included in this PR?
Are these changes tested?
Yes! There is a nested recursive query in the test file
Are there any user-facing changes?
Nested recursive queries are now allowed instead of failing with a "not implemented" error