Re: [PATCHES] [pgsql-patches] Phantom Command IDs, updated patch

Tom Lane wrote:
> Bruce Momjian <bruce(at)momjian(dot)us> writes:
> > The way combo cid is supposed to work is that you are deleting a row
> > created in your same transaction by a previous command id, so you look
> > in the combo cid array to see if a match for that pair exists --- if
> > not, you create a new entry and put the two cids on it.
>
> > So, with the combo lock cid, you do the same process, and lookups of who
> > holds the lock looks at the cid combo, and if the second subtransaction
> > was aborted, the first one is the lock holder. If you again lock the
> > row, you create a new combo cid and use the original cid there because
> > the second cid was aborted.
>
> No, because no process other than the originator can see the combo-cid
> data structure, and for locking situations you really need other
> backends to be able to know whether the tuple is locked and how.

Oh, OK, I forgot pg_subtrans is visible to all backends.

> But I think my proposal of extending MultiXact would fix it; please look
> at that.

Sounds good.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://www.enterprisedb.com

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