Quoting Bill Chandler <billybobc1210(at)yahoo(dot)com>:
> ... The normal activity is to delete 3-5% of the rows per day,
> followed by a VACUUM ANALYZE.
> However, on occasion, deleting 75% of rows is a
> legitimate action for the client to take.
> > In case nobody else has asked: is your max_fsm_pages
> > big enough to handle all the deleted pages,
> > across ALL tables hit by the purge?
> This parameter is most likely set incorrectly. So
> that could be causing problems. Could that be a
> culprit for the index bloat, though?
Look at the last few lines of vacuum verbose output.
It will say something like:
free space map: 55 relations, 88416 pages stored; 89184 total pages needed
Allocated FSM size: 1000 relations + 1000000 pages = 5920 kB shared memory.
"1000000" here is [max_fsm_pages] from my postgresql.conf.
If the "total pages needed" is bigger than the pages
fsm is allocated for, then you are bleeding.
"Dreams come true, not free." -- S.Sondheim, ITW
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