| From: | Pavan Deolasee <pavan(dot)deolasee(at)gmail(dot)com> |
|---|---|
| To: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
| Cc: | Peter Geoghegan <pg(at)bowt(dot)ie>, Robert Haas <robertmhaas(at)gmail(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org>, Andrew Dunstan <andrew(dot)dunstan(at)2ndquadrant(dot)com>, Pavan Deolasee <pavan(dot)deolasee(at)2ndquadrant(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: [HACKERS] MERGE SQL Statement for PG11 |
| Date: | 2018-02-12 08:18:40 |
| Message-ID: | CABOikdM2pr08Ojq9ccLssrCVFWmD-mycr876QC-sstxULVQvFA@mail.gmail.com |
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| Thread: | |
| Lists: | pgsql-hackers |
On Sat, Feb 10, 2018 at 7:19 AM, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)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/
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