| From: | Bruce Momjian <bruce(at)momjian(dot)us> |
|---|---|
| To: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
| Cc: | pgsql-hackers(at)postgresql(dot)org, Merlin Moncure <mmoncure(at)gmail(dot)com>, Gregory Stark <stark(at)enterprisedb(dot)com>, Csaba Nagy <nagy(at)ecircle-ag(dot)com>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Chris Browne <cbbrowne(at)acm(dot)org>, Jochem van Dieten <jochemd(at)gmail(dot)com>, Dimitri Fontaine <dfontaine(at)hi-media(dot)com>, Hannu Krosing <hannu(at)2ndQuadrant(dot)com>, Richard Huxton <dev(at)archonet(dot)com> |
| Subject: | Re: Transaction Snapshots and Hot Standby |
| Date: | 2008-09-25 01:19:45 |
| Message-ID: | 200809250119.m8P1JjM03274@momjian.us |
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| Lists: | pgsql-hackers |
Simon Riggs wrote:
> 2. Master ignores Standby's OldestXmin
> Effects:
> * Long running queries on standby...
> Have no effect on primary
> Can delay apply of WAL records on standby
> * Queries on standby give consistent answers in all cases.
Just for clarification, if you set a max_slave_delay it means it is the
maximum amount of time WAL replay can be delayed on the slave, _and_ it
is the maximum amount of time a query/snapshot can be guaranteed to run
without the possibility of being canceled. My point is that these two
concepts are linked to the same setting.
--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ If your life is a hard drive, Christ can be your backup. +
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