| From: | Markus Wanner <markus(at)bluegap(dot)ch> |
|---|---|
| To: | ITAGAKI Takahiro <itagaki(dot)takahiro(at)oss(dot)ntt(dot)co(dot)jp> |
| Cc: | Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Simon Riggs <simon(at)2ndQuadrant(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Synchronous Log Shipping Replication |
| Date: | 2008-09-09 11:22:06 |
| Message-ID: | 48C65C5E.90100@bluegap.ch |
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| Lists: | pgsql-hackers |
Hi,
ITAGAKI Takahiro wrote:
> Signals and locking, borrewed from Postgres-R, are now studied
> for the purpose in the log shipping, but I'm not sure it can be
> also used in the group commit.
Yeah. As Heikki points out, there is a completely orthogonal question
WRT group commit: how does transaction A know if or how long it should
wait for other transactions to file their WAL?
If we decide to do all of the WAL writing from a separate WAL writer
process and let the backends communicate with it, then imessages might
help again. But I currently don't think that's feasible.
Apart from possibly having similar IPC requirements, group commit and
log shipping have not much in common and should be considered separate
features.
Regards
Markus Wanner
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