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
