The comment I have from Tom Lane on this patch is:
band-aid solution to just one aspect of problem ...
so I am afraid I am going to have to reject it. Sorry.
---------------------------------------------------------------------------
Mark Kirkwood wrote:
> I encountered this bug recently - and thought I'd have a try at seeing
> what might fix it.
>
> Taking an exclusive lock on the to-be-dropped table immediately (i.e in
> RemoveRel) seems to be enough to prevent the drop starting while an
> index is being created in another session. So it "fixes" the issue -
> possible objections that I can think of are:
>
> 1/ Not a general solution to multi session dependent drop/create of
> objects other than tables (unless we do 2/)
> 2/ Using this approach in all object dropping code may result in
> deadlocks (but is this worse than dangling/mangled objects?)
>
> Now, I'm conscious that there could be other show stopper reasons for
> *not* doing this that I have not thought of, but figured I'd post in
> case the idea was useful. Thoughts?
>
> Cheers
>
> Mark
[ text/x-patch is unsupported, treating like TEXT/PLAIN ]
> *** src/backend/commands/tablecmds.c.orig Wed Jan 2 13:58:05 2008
> --- src/backend/commands/tablecmds.c Wed Jan 2 13:46:43 2008
> ***************
> *** 514,519 ****
> --- 514,522 ----
> object.objectId = relOid;
> object.objectSubId = 0;
>
> + //Try a lock here!
> + LockRelationOid(relOid, ExclusiveLock);
> +
> performDeletion(&object, behavior);
> }
>
>
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--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://postgres.enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +