On Wed, Sep 3, 2025 at 11:05 PM Peter Eisentraut <pe...@eisentraut.org> wrote: > We (I) missed expanding virtual generated columns in > get_relation_constraints() in plancat.c. That way, some opportunities > for constraint exclusion will be missed if a constraint contains virtual > generated columns, as can be shown in the attached test case (thanks to > Richard Guo). Simple fix attached.
I'm afraid this fix isn't thorough: it covers only CHECK constraints
but not NOT NULL or partitioning constraints. For example,
create table vt (a int, b int generated always as (a * 2) virtual not null);
set constraint_exclusion to on;
explain (costs off) select * from vt where b is null;
QUERY PLAN
-----------------------------
Seq Scan on vt
Filter: ((a * 2) IS NULL)
(2 rows)
We should get a dummy Result rather than a SeqScan.
What I have in mind is something like the attached v2, which covers
all types of constraints.
- Richard
v2-0001-Expand-virtual-generated-columns-in-constraint-ex.patch
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