Re: simple question

> > Is this correct?
> >
> > vacuum by itself just cleans out the old extraneous tuples so that they
> > aren't in the way anymore
>
> Actually it puts the free space in each page on a list (the free space
> map) so it can be reused for new tuples without having to allocate
> fresh pages.  It finds free space by looking for tuples that can't be
> seen any more by any transaction.
>
> > vacuum analyze rebuilds indexes.  If you add an index to a table it
won't be
> > used until you vacuum analyze it
>
> It doesn't rebuild indexes--REINDEX does that.  ANALYZE measures the
> size and statistics of the data in the table, so the planner can do a
> good job.

Is REINDEX something that needs to be done on a periodic basis?

> > vacuum full actually compresses the table on disk by reclaiming the
space
> > from the old tuples after they have been removed.
>
> It moves tuples around and frees up pages at the end of the table,
> thus compacting it.
>
> So you're mostly wrong on all three.  :)
>
> -Doug
>

Thanks!

Rick