Thread: SnapshotResetXmin

SnapshotResetXmin is called 3 times after each statement in
ReadCommitted mode.

Too keen, perhaps?

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

Simon Riggs wrote:
> 
> SnapshotResetXmin is called 3 times after each statement in
> ReadCommitted mode.
> 
> Too keen, perhaps?

It is called each time a snapshot is unregistered and each time an
active snapshot is popped.  I don't see any way to reduce the number of
calls without complicating the code a lot ... do you have any ideas?

Maybe we could check whether TransState is not TRANS_INPROGRESS and skip
it in those cases ...?

-- 
Alvaro Herrera                                http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support

Alvaro Herrera <alvherre@commandprompt.com> writes:
> Simon Riggs wrote:
>> SnapshotResetXmin is called 3 times after each statement in
>> ReadCommitted mode.

> Maybe we could check whether TransState is not TRANS_INPROGRESS and skip
> it in those cases ...?

Surely this would take longer than the function itself does.  What's
the point of worrying at all?
        regards, tom lane

On Fri, 2009-01-16 at 12:13 -0500, Tom Lane wrote:
> Alvaro Herrera <alvherre@commandprompt.com> writes:
> > Simon Riggs wrote:
> >> SnapshotResetXmin is called 3 times after each statement in
> >> ReadCommitted mode.
> 
> > Maybe we could check whether TransState is not TRANS_INPROGRESS and skip
> > it in those cases ...?
> 
> Surely this would take longer than the function itself does.  What's
> the point of worrying at all?

I thought it *might* be indicative of over zealous coding, thats all.

Better a false-positive than to miss a possible issue. 

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