Re: Transaction Snapshots and Hot Standby

From: Csaba Nagy <nagy(at)ecircle-ag(dot)com>
To: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
Cc: Merlin Moncure <mmoncure(at)gmail(dot)com>, Gregory Stark <stark(at)enterprisedb(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Richard Huxton <dev(at)archonet(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Transaction Snapshots and Hot Standby
Date: 2008-09-11 12:39:25
Message-ID: 1221136765.17270.75.camel@PCD12478
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On Thu, 2008-09-11 at 15:23 +0300, Heikki Linnakangas wrote:
> I'd imagine that even if applying the WAL on the slave is blocked, it's
> still streamed from the master to the slave, and in case of failover the
> slave will fast-forward before starting up as the new master.

Which begs the question: what happens with a query which is running on
the slave in the moment when the slave switches from recovery mode and
starts up ? Should the running queries be canceled if they are blocking
applying of WAL, to allow start-up, or let them finish ?

Cheers,
Csaba.

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