Re: INSERT waiting under heavy load

On Fri, Jan 06, 2006 at 04:49:09PM -0500, Tom Lane wrote:
> performance risk in the sort of scenario you are describing.
> (I'm not sure why it would manifest as transactions showing "INSERT
> waiting" state though.)

It's because of I/O. When you have a large number of updates, the
planner always assumes an indexscan (correctly), but you end up
scanning megabytes of dead tuples. With a large number of open
transactions, most of the time VACUUM can't recover the space. I
agree with what Tom said earlier in this thread: the design is
guaranteed to lose.

A

--
Andrew Sullivan | ajs(at)crankycanuck(dot)ca
"The year's penultimate month" is not in truth a good way of saying
November.
--H.W. Fowler