Re: pg_last_xact_insert_timestamp

On Thu, Sep 8, 2011 at 6:14 AM, Fujii Masao <masao.fujii@gmail.com> wrote:
> OTOH, new function enables users to monitor the delay as a timestamp.
> For users, a timestamp is obviously easier to handle than LSN, and the delay
> as a timestamp is more intuitive. So, I think that it's worth adding
> something like pg_last_xact_insert_timestamp into core for improvement
> of user-friendness.

It seems very nice from a usability point of view, but I have to agree
with Simon's concern about performance.  Actually, as of today,
WALInsertLock is such a gigantic bottleneck that I suspect the
overhead of this additional bookkeeping would be completely
unnoticeable.  But I'm still reluctant to add more centralized
spinlocks that everyone has to fight over, having recently put a lot
of effort into getting rid of some of the ones we've traditionally
had.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company