Re: Synchronization levels in SR

On Mon, 2010-09-06 at 22:32 +0200, Boszormenyi Zoltan wrote:
> (in commit)
> write wal record
> release locks/etc   <xact2 can proceed from here
> wait for sync ack
> 
> In the first case, the contention is obviously increased.
> With this, we are creating more idle time in the server
> instead of letting other transactions do their jobs as soon
> as possible. The second method was implemented in my
> patch. Are there any drawbacks with this? 

Then I respectfully suggest that you're releasing locks too early.

Your proposal would allow a 2nd user to see the results of the 1st
user's transaction before the 1st user knew about whether it had
committed or not.

I know why you want that, but I don't think its right.

This has very little, if anything, to do with mixing async/sync
connections. You make it sound like all transactions always wait for
other transactions, which they definitely don't, especially in
reasonably well designed applications.

-- Simon Riggs           www.2ndQuadrant.comPostgreSQL Development, 24x7 Support, Training and Services