Re: should ConstraintRelationId ins/upd cause relcache invals?

Hi,

On 2019-01-21 16:27:50 -0300, Alvaro Herrera wrote:
> While working on bugfixes for FK problems in partitioned tables, I came
> across some behavior that appears to stem from our inclusion of foreign
> keys in relcache, without sufficient care for invalidating the relcache
> entries when the foreign key set for the table changes.  (Namely, a
> partition retains its relcache entry with no FKs when an FK is added to
> the parent table, leading a DELETE to skip running action triggers).
> 
> At https://postgr.es/m/201901182216.nr5clsxrn624@alvherre.pgsql I posted
> a simplistic for the specific problem I found by calling
> CacheInvalidateRelcache in the problem spot.  But I'm wondering if the
> correct fix isn't to have CacheInvalidateHeapTuple deal with FK
> pg_constraint tuples instead, per the attached patch.  Why does this not
> lead to stale cache problems elsewhere?
> 
> FKs were added to relcache entries by commit 100340e2dcd0 ("Restore
> foreign-key-aware estimation of join relation sizes"), so CCing Tom and
> Tomas.

I wondered about the same in https://www.postgresql.org/message-id/20180628150209.n2qch5jtn3vt2xaa%40alap3.anarazel.de
, just about pg_index, but people didn't like it much.

Greetings,

Andres Freund