On Feb 25, 2008, at 2:59 PM, Stephen Denne wrote:
Please know that I'm very new at advising PostgreSQL users how they
should tune their system...
I'd never have known it if you hadn't said anything
My understanding of your vacuum verbose output was that it was
pointing out that max_fsm_pages was currently smaller than 281727,
so therefore there was no way it could contain mappings to all the
reusable space. However I don't think it is hinting at, nor
recommending a value that you should be using.
If you do nothing, then this number of pages with reusable space
will probably continue to grow, therefore, it probably has been
growing.
So, for example, if your max_fsm_pages is currently only 20000, then
perhaps 20000 of the 281727 pages with reusable space are in the
free space map. The remaining 260000 pages _may_ have been generated
through 20 different processes each of which created 13000 more
pages with reusable space than the map could reference. If that was
the case, then a max_fsm_pages of 33000 might be large enough.
Do you see what I'm getting at?
I think that you should do a vacuum full of that table once, then
monitor the number of pages in it with reusable space for a while
(over a few iterations of your regular processes). That should give
you information about how much larger your max_fsm_pages should be
than it currently is.
This sounds sane to me, will do. Thanks again!
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