Horton

Re: [HACKERS] MERGE SQL Statement for PG11

Pavan Deolasee <pavan.deolasee@gmail.com>

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From: Pavan Deolasee <pavan.deolasee@gmail.com>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: Peter Geoghegan <pg@bowt.ie>, Robert Haas <robertmhaas@gmail.com>, Simon Riggs <simon@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: 2018-02-12T08:18:40Z
Lists: pgsql-hackers 
On Sat, Feb 10, 2018 at 7:19 AM, Tomas Vondra <tomas.vondra@2ndquadrant.com>
wrote:

> Hi,
>
> On 02/07/2018 10:24 AM, Pavan Deolasee wrote:
> >
>
>        if (startWAL < GetXactWALBytes())
>            ereport(ERROR,
>                    (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
>                     errmsg("cannot write to database ...")));
>
> I think this actually fails to enforce the rule, because some writes may
> not produce WAL (think of unlogged tables). I also suspect it may be
> incorrect "in the opposite direction" because a query may not do any
> changes and yet it may produce WAL (e.g. due to wal_hint_bits=true).
>
> So we may need to think of a different way to enforce this ...


Yes, this does look problematic.

Thanks,
Pavan

-- 
 Pavan Deolasee                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

Commits

  1. Add support for MERGE SQL command

  2. Add API of sorts for transition table handling in trigger.c

  3. Revert MERGE patch

  4. Fix several bugs related to ON CONFLICT's EXCLUDED pseudo relation.