Re: Transaction Snapshots and Hot Standby - Mailing list pgsql-hackers

From Bruce Momjian
Subject Re: Transaction Snapshots and Hot Standby
Date
Msg-id 200809250119.m8P1JjM03274@momjian.us
Whole thread Raw
In response to Re: Transaction Snapshots and Hot Standby  (Simon Riggs <simon@2ndQuadrant.com>)
Responses Re: Transaction Snapshots and Hot Standby  (Bruce Momjian <bruce@momjian.us>)
Re: Transaction Snapshots and Hot Standby  (Simon Riggs <simon@2ndQuadrant.com>)
Re: Transaction Snapshots and Hot Standby  (Zeugswetter Andreas OSB sIT <Andreas.Zeugswetter@s-itsolutions.at>)
List 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@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + If your life is a hard drive, Christ can be your backup. +


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