Re: Synchronous replication patch v2

Simon Riggs wrote:
> On Fri, 2008-11-14 at 19:00 +0200, Heikki Linnakangas wrote:
>> Why do we need a separate XLogsndRqst variable in shared memory? Don't 
>> we always want to send the WAL up to the same point as we flush it?
> 
> If we're doing synch rep and we're committing.

You flush and send the WAL, up to the same point?

> What happens when we're
> doing async rep or running something like a large load. 

You don't flush, and you don't request the WAL to be sent? The 
background writer and WAL sender can still wake up periodically, and 
write and send the WAL as they find convenient.

> I wouldn't want
> to presume that the network packet size and the disk write size are
> always identical.

Huh? No-one's presuming that.

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