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| author | Tom Lane <tgl@sss.pgh.pa.us> | 2024-11-19 18:26:19 -0500 |
|---|---|---|
| committer | Tom Lane <tgl@sss.pgh.pa.us> | 2024-11-19 18:26:19 -0500 |
| commit | a43d7a8c7cce00e3fcf330e201a3a94f97097e64 (patch) | |
| tree | bc904a12d7c34a9a1f30617434e403fb5c756b8f /src/backend/utils/adt/ruleutils.c | |
| parent | c166454496876818216e222890ab1ae788551c42 (diff) | |
| download | postgresql-a43d7a8c7cce00e3fcf330e201a3a94f97097e64.tar.gz postgresql-a43d7a8c7cce00e3fcf330e201a3a94f97097e64.zip | |
Compare collations before merging UNION operations.
In the dim past we figured it was okay to ignore collations
when combining UNION set-operation nodes into a single N-way
UNION operation. I believe that was fine at the time, but
it stopped being fine when we added nondeterministic collations:
the semantics of distinct-ness are affected by those. v17 made
it even less fine by allowing per-child sorting operations to
be merged via MergeAppend, although I think we accidentally
avoided any live bug from that.
Add a check that collations match before deciding that two
UNION nodes are equivalent. I also failed to resist the
temptation to comment plan_union_children() a little better.
Back-patch to all supported branches (v13 now), since they
all have nondeterministic collations.
Discussion: https://postgr.es/m/3605568.1731970579@sss.pgh.pa.us
Diffstat (limited to 'src/backend/utils/adt/ruleutils.c')
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