I believe the more frequently you vacuum, the faster it will go, so that may be the driving factor in deciding. Personally, each day, I'd add the new tuples then remove the no-longer needed tuples, make sure max_fsm_pages is large enough to handle all the pages removed in the largest table, then run a vacuum analyze on the table or entire database. Run it each night and it will be nice and fast and you shouldn't ever need to worry about locking the entire table with a vacuum full or spend time to re-create the table and indicies.
That's what I do which I think is the most automated,maintainance-free solution. I currently run a lazy vacuum analyze each night after making my large changes. My tables don't change enough during the day to require mid-day vacuums.
--Michael
Joshua Daniel Franklin wrote:
I played with this tonight writing a small insert/update routine and
frequent vacuums. Here is what I came up with ( (PostgreSQL) 7.2.1 )
This is some great info, thanks.
In addition, max_fsm_pages has an impact on how many pages will be
available to be marked as re-usable. If you have a huge table and
changes are impacting more than the default 10,000 pages this is set to,
you will want to bump this number up. My problem was I saw my UnUsed
tuples always growing and not being re-used until I bumped this value
up. As I watched the vacuum verbose output each run, I notices more
than 10k pages were in fact changing between vacuums.
This has made me think about something we've been doing. We've got one
db that is used basically read-only; every day ~15000 records are added,
but very rarely are any deleted. What we've been doing is just letting it
sit until it gets close to too big for the filesystem, then lopping off
the earliest 6 months worth of records. The question is, is it best
to do this then set the max_fsm_pages to a huge number and vacuum full?
Or should I change it so scripts remove the oldest day and vacuum before
adding the next days?
Or just rebuild the db every time. :)
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