| From: | Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at> |
|---|---|
| To: | "Shigeru Hanada *EXTERN*" <shigeru(dot)hanada(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Kohei KaiGai <kaigai(at)kaigai(dot)gr(dot)jp>, Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: FDW for PostgreSQL |
| Date: | 2013-02-14 09:45:04 |
| Message-ID: | A737B7A37273E048B164557ADEF4A58B057B3258@ntex2010a.host.magwien.gv.at |
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| Lists: | pgsql-hackers |
Shigeru Hanada wrote:
> Tom Lane wrote:
>> It ought to be pulling the rows back a few at a time, and
>> that's not going to work well if multiple scans are sharing the same
>> connection. (We might be able to dodge that by declaring a cursor
>> for each scan, but I'm not convinced that such a solution will scale up
>> to writable foreign tables, nested queries, subtransactions, etc.)
>
> Indeed the FDW used CURSOR in older versions. Sorry for that I have
> not looked writable foreign table patch closely yet, but it would
> require (may be multiple) remote update query executions during
> scanning?
It would for example call ExecForeignUpdate after each call to
IterateForeignScan that produces a row that meets the UPDATE
condition.
Yours,
Laurenz Albe
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