| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at> |
| Cc: | "Etsuro Fujita *EXTERN*" <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>, "Shigeru Hanada *EXTERN*" <shigeru(dot)hanada(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Optimization for updating foreign tables in Postgres FDW |
| Date: | 2014-08-27 13:56:59 |
| Message-ID: | CA+TgmobP53EE+4SfXY7-as4X41TVuXjgEPxkTzFcoWQDKVq=wg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Mon, Aug 25, 2014 at 8:58 AM, Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at> wrote:
> Reading the code, I noticed that the pushed down UPDATE or DELETE statement is executed
> during postgresBeginForeignScan rather than during postgresIterateForeignScan.
> It probably does not matter, but is there a reason to do it different from the normal scan?
Hmm, I'm worried that may be an API contract violation. ISTM that we
might initialize nodes that we never read from - they can show up in
the EXPLAIN-plan as (never executed) - and things that aren't executed
shouldn't do work, especially work that permanently modifies data.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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