Vacuum (table performance)

Hello

Here we have a couple of tables with very high rotation: on one of them,
rows get inserted all the time from 2 up to 15 per second, depending on
application level of activity. Each row has a mean life of about 3 hours,
when it gets copied to another table and deleted, along with a bunch of
similar ones. This is done by a pgpsql function which is invoked on a
regular basis. Following each execution of this function we run a vacuum on
the table. However, we are seeing increasing execution times, not for the
function but for the vacuum itself. Currently we are getting about 9 minutes
for the vacuum, with a table of 45K records. This creeped up from a few
seconds past week, when the table was reinitialized. However table size is
approximately constant all the time.

Are there other mechanisms to do online maintenance of a table? I must
stress the word 'online' since this is a real time application which must be
up all the time.

thanks in advance
cl.

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