Re: maintaining a reference to a fetched row

Brian Karlak <zenkat(at)metaweb(dot)com> writes:
> On Nov 4, 2009, at 8:47 AM, Jeff Janes wrote:
>> Why would the index scan take 1 ms two of the times it is done but 5ms
>> the third time? Isn't it the same index scan each time? Or does the
>> change in queue.status change the plan?

> The final update is a different query -- just a plain old update by ID:
> UPDATE queue_proc set status = 'proc' where id = %s ;
> This update by ID takes ~2.5ms, which means it's where the framework
> is spending most of its overhead.

Well, if SELECT FROM queue_proc where id = %s takes 1ms and the update
takes 2.5ms, then you've got 1.5ms going into updating the row, which
means it's not going to get a whole lot faster by switching to some
other WHERE condition. Maybe you should look at cutting back on indexes
and/or triggers attached to this table.

regards, tom lane