Re: Synchronous Log Shipping Replication - Mailing list pgsql-hackers

From Markus Wanner
Subject Re: Synchronous Log Shipping Replication
Date
Msg-id 48C65C5E.90100@bluegap.ch
Whole thread Raw
In response to Re: Synchronous Log Shipping Replication  (ITAGAKI Takahiro <itagaki.takahiro@oss.ntt.co.jp>)
List 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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