Re: Why vacuum?

On Wed, 13 Dec 2000, bpalmer wrote:

> > Yes, postgresql requires vacuum quite often otherwise queries and
> > updates start taking ungodly amounts of time to complete.  If you're
> > having problems because vacuum locks up your tables for too long
> > you might want to check out:
> 
> But why?  I don't know of other databases that need to be 'vacuum'ed.  Do
> all others just do it internaly on a regular basis?
> 
> What am I missing here?

PgSQL's storage manager is currently such that it doesn't overwrite
'deleted' records, but just keeps appending to the end of the table
... so, for instance, a client of ours whose table had 5 records in it
that are updated *alot* grew a table to 64Meg that only contains ~8k worth
of data ...

vacuum'ng cleans out the cruft and truncates the file ...

vadim, for v7.2, is planning on re-writing the storage manager to do
proper overwriting of deleted space, which will reduce the requirement for
vacuum to almost never ...