Re: [HACKERS] Leftover invalidation handling in RemoveRelations

On Wed, Mar 15, 2017 at 2:40 PM, Andres Freund <andres@anarazel.de> wrote:
> reviewing some citus code copied from postgres I noticed that
> RemoveRelations() has the following bit:
>
>                 /*
>                  * These next few steps are a great deal like relation_openrv, but we
>                  * don't bother building a relcache entry since we don't need it.
>                  *
>                  * Check for shared-cache-inval messages before trying to access the
>                  * relation.  This is needed to cover the case where the name
>                  * identifies a rel that has been dropped and recreated since the
>                  * start of our transaction: if we don't flush the old syscache entry,
>                  * then we'll latch onto that entry and suffer an error later.
>                  */
>                 AcceptInvalidationMessages();
>
>                 /* Look up the appropriate relation using namespace search. */
>                 state.relkind = relkind;
>                 state.heapOid = InvalidOid;
>                 state.concurrent = drop->concurrent;
>                 relOid = RangeVarGetRelidExtended(rel, lockmode, true,
>                                                                                   false,
>                                                                                   RangeVarCallbackForDropRelation,
>                                                                                   (void *) &state);
>
> which doesn't seem to make sense - RangeVarGetRelidExtended does
> invalidation handling on it's own.
>
> Looks like this was left there in the course of
> http://git.postgresql.org/gitweb/?p=postgresql.git;a=commit;h=2ad36c4e44c8b513f6155656e1b7a8d26715bb94
>
> ISTM AcceptInvalidationMessages() and preceding comment should just be
> removed?

Yeah, I don't think that would hurt anything.

(I'm not sure it'll help anything either - the overhead of an extra
AcceptInvalidationMessages() call is quite minimal - but, as you say,
maybe it's worth doing just to discourage future code authors from
including unnecessary fluff.)

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company