Re: A long-running transaction

On Tue, Apr 03, 2007 at 10:16:13PM +0800, John Summerfield wrote:
> It is hitting the disk pretty hard now on this machine, but the laptop's
> still going too, and the disk seems to run about half the time, part of
> a second running, part idle (but the intervals are getting shorter).
>
> It struck me as fairly curious that neither postgresql nor the
> application was hogging the CPU.

Why? Nothing about this seems likely CPU bound. It's probably I/O.
I note is number:

> IOwait: 2d 0:46:37.33 28.5% page dea: 16218135

which is pretty awful. Also

> For each record, I update a non-key field in another table; the source
> data for that other table is less than a megabyte.

this is a real issue. Basically, you're constrained at the rotation
speed of your disk, because for each record, you have to first find
then update one row somewhere else.

A

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