| From: | David Rowley <dgrowleyml(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Andy Fan <zhihui(dot)fan1213(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Ashutosh Bapat <ashutosh(dot)bapat(dot)oss(at)gmail(dot)com>, rushabh(dot)lathia(at)gmail(dot)com |
| Subject: | Re: [PATCH] Keeps tracking the uniqueness with UniqueKey |
| Date: | 2020-04-03 04:07:54 |
| Message-ID: | CAApHDvrhOMPZKSugH6jnTCNFC2Nb+KGcXegJoas2FBvvSkDe-A@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, 3 Apr 2020 at 16:40, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> (It occurs to me BTW that we've been overly conservative about using
> NOT NULL constraints in planning, because of failing to consider that.
> Addition or drop of NOT NULL has to cause a change in
> pg_attribute.attnotnull, which will definitely cause a relcache inval
> on its table, cf rules in CacheInvalidateHeapTuple(). So we *don't*
> need to have a pg_constraint entry corresponding to the NOT NULL, as
> we've mistakenly supposed in some past discussions.)
Agreed for remove_useless_groupby_columns(), but we'd need it if we
wanted to detect functional dependencies in
check_functional_grouping() using unique indexes.
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