Re: Hot standby, running xacts, subtransactions

Simon Riggs wrote:
> On Wed, 2009-02-25 at 22:39 +0200, Heikki Linnakangas wrote:
> 
>> When we take the snapshot of running transactions in the master, in 
>> GetRunningTransactionData(), it only includes top-level xids and those 
>> subxids that are in the subxid caches. Overflowed subxids are not 
>> included. Isn't that a problem? When the standby initializes the 
>> recovery procs using the running xacts information, pg_subtrans doesn't 
>> isn't set for the overflowed xids, because that information is not 
>> included in the WAL record. If you're lucky, the information is there 
>> already, but we don't generally guarantee pg_subtrans to survive crash 
>> or restart.
> 
> That is exactly the reason why we don't treat an overflowed snapshot as
> a valid starting point.

We don't? I don't see anything stopping it.

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com