| From: | "tsunakawa(dot)takay(at)fujitsu(dot)com" <tsunakawa(dot)takay(at)fujitsu(dot)com> |
|---|---|
| To: | 'Masahiko Sawada' <masahiko(dot)sawada(at)2ndquadrant(dot)com> |
| Cc: | Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Fujii Masao <masao(dot)fujii(at)oss(dot)nttdata(dot)com>, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>, Muhammad Usama <m(dot)usama(at)gmail(dot)com>, Masahiro Ikeda <ikedamsh(at)oss(dot)nttdata(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, amul sul <sulamul(at)gmail(dot)com>, Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com>, Álvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Ildar Musin <ildar(at)adjust(dot)com>, Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, Chris Travers <chris(dot)travers(at)adjust(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Tatsuo Ishii <ishii(at)sraoss(dot)co(dot)jp> |
| Subject: | RE: Transactions involving multiple postgres foreign servers, take 2 |
| Date: | 2020-10-19 05:38:56 |
| Message-ID: | TYAPR01MB2990FD70F1B20952979D10D5FE1E0@TYAPR01MB2990.jpnprd01.prod.outlook.com |
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| Lists: | pgsql-hackers |
From: Masahiko Sawada <masahiko(dot)sawada(at)2ndquadrant(dot)com>
> > Unfortunately, I'm afraid we can do nothing about it. If the DBMS's client
> library doesn't support cancellation (e.g. doesn't respond to Ctrl+C or provide a
> function that cancel processing in pgorogss), then the Postgres user just finds
> that he can't cancel queries (just like we experienced with odbc_fdw.)
>
> So the idea of using another process to commit prepared foreign
> transactions seems better also in terms of this point. Even if a DBMS
> client library doesn’t support query cancellation, the transaction
> commit can return the control to the client when the user press ctl-c
> as the backend process is just sleeping using WaitLatch() (it’s
> similar to synchronous replication)
I have to say that's nitpicking. I believe almost nobody does, or cares about, canceling commits, at the expense of impractical performance due to non-parallelism, serial execution in each resolver, and context switches.
Also, FDW is not cancellable in general. It makes no sense to care only about commit.
(Fortunately, postgres_fdw is cancellable in any way.)
Regards
Takayuki Tsunakawa
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