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| author | Richard Guo <rguo@postgresql.org> | 2024-10-09 17:19:04 +0900 |
|---|---|---|
| committer | Richard Guo <rguo@postgresql.org> | 2024-10-09 17:19:04 +0900 |
| commit | 67a54b9e83d331eadd3a595e6c3bfec06288d2c4 (patch) | |
| tree | 98bde85da279ae7a3f0441323e32d00eb8f46697 /src/tutorial/complex.c | |
| parent | 828e94c9d2fd87c06a75354361543119d9937068 (diff) | |
Allow pushdown of HAVING clauses with grouping sets
In some cases, we may want to transfer a HAVING clause into WHERE in
hopes of eliminating tuples before aggregation instead of after.
Previously, we couldn't do this if there were any nonempty grouping
sets, because we didn't have a way to tell if the HAVING clause
referenced any columns that were nullable by the grouping sets, and
moving such a clause into WHERE could potentially change the results.
Now, with expressions marked nullable by grouping sets with the RT
index of the RTE_GROUP RTE, it is much easier to identify those
clauses that reference any nullable-by-grouping-sets columns: we just
need to check if the RT index of the RTE_GROUP RTE is present in the
clause. For other HAVING clauses, they can be safely pushed down.
Author: Richard Guo
Discussion: https://postgr.es/m/CAMbWs4-NpzPgtKU=hgnvyn+J-GanxQCjrUi7piNzZ=upiCV=2Q@mail.gmail.com
Diffstat (limited to 'src/tutorial/complex.c')
0 files changed, 0 insertions, 0 deletions