Horton

Re: [HACKERS] MERGE SQL Statement for PG11

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Pavan Deolasee <pavan.deolasee@gmail.com>, Simon Riggs <simon@2ndquadrant.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Andrew Dunstan <andrew.dunstan@2ndquadrant.com>, Pavan Deolasee <pavan.deolasee@2ndquadrant.com>, Stephen Frost <sfrost@snowman.net>, PostgreSQL-development <pgsql-hackers@postgresql.org>
Date: 2018-03-24T17:48:46Z
Lists: pgsql-hackers 
On Sat, Mar 24, 2018 at 5:27 AM, Robert Haas <robertmhaas@gmail.com> wrote:
> If it's possible to identify the two OIDs that are supposed to match
> and cross-check that the OIDs are the same, then we could just bomb
> out with an error if they aren't.  That's not lovely, and is basically
> a hack, but it's possible that no better fix is possible in the time
> we have, and it's wouldn't be any worse than this crock from copy.c:
>
>             if (!list_member_oid(plan->relationOids, queryRelId))
>                 ereport(ERROR,
>                         (errcode(ERRCODE_OBJECT_NOT_IN_PREREQUISITE_STATE),
>                          errmsg("relation referenced by COPY statement
> has changed")));

That's definitely all we have time for. The only alternative is to rip
out support for partitioning, as partitioning is the only thing that
necessitates the use of multiple RTEs. I don't think it would make
sense to use a second RTE only when needed.

-- 
Peter Geoghegan

Commits

  1. Add support for MERGE SQL command

  2. Avoid repeated name lookups during table and index DDL.

  3. Use an MVCC snapshot, rather than SnapshotNow, for catalog scans.