Don't allow CTEs to determine semantic levels of aggregates. The fix for bug #19055 (commit b0cc0a71e) allowed CTE references in sub-selects within aggregate functions to affect the semantic levels assigned to such aggregates. It turns out this broke some related cases, leading to assertion failures or strange planner errors such as "unexpected outer reference in CTE query". After experimenting with some alternative rules for assigning the semantic level in such cases, we've come to the conclusion that changing the level is more likely to break things than be helpful.
Therefore, this patch undoes what b0cc0a71e changed, and instead installs logic to throw an error if there is any reference to a CTE that's below the semantic level that standard SQL rules would assign to the aggregate based on its contained Var and Aggref nodes. (The SQL standard disallows sub-selects within aggregate functions, so it can't reach the troublesome case and hence has no rule for what to do.) Perhaps someone will come along with a legitimate query that this logic rejects, and if so probably the example will help us craft a level-adjustment rule that works better than what b0cc0a71e did. I'm not holding my breath for that though, because the previous logic had been there for a very long time before bug #19055 without complaints, and that bug report sure looks to have originated from fuzzing not from real usage. Like b0cc0a71e, back-patch to all supported branches, though sadly that no longer includes v13. Bug: #19106 Reported-by: Kamil Monicz <[email protected]> Author: Tom Lane <[email protected]> Discussion: https://postgr.es/m/[email protected] Backpatch-through: 14 Branch ------ REL_18_STABLE Details ------- https://git.postgresql.org/pg/commitdiff/12bc3291772e29fdf2850c890ba9b962b07a1c1c Modified Files -------------- src/backend/parser/parse_agg.c | 49 ++++++++++++++++++++++++++-------- src/test/regress/expected/with.out | 54 ++++++++++++++++++++++---------------- src/test/regress/sql/with.sql | 22 +++++++++++----- 3 files changed, 85 insertions(+), 40 deletions(-)
