Re: [SQL] Performance - Mailing list pgsql-sql

Depends on the indices that have to be gone through.  It can take quite a
while.

--
--
Karl Denninger (karl@denninger.net) http://www.mcs.net/~karl
I ain't even *authorized* to speak for anyone other than myself, so give
up now on trying to associate my words with any particular organization.


On Wed, Mar 10, 1999 at 01:27:20PM -0500, Jason Slagle wrote:
> And how long is normal for Vacuum analyze to take on bout 350 megs of
> DATA?
>
> Jason
>
> ---
> Jason Slagle
> Network Administrator - Toledo Internet Access - Toledo Ohio
> - raistlin@tacorp.net - jslagle@toledolink.com - WHOIS JS10172
>
> On Wed, 10 Mar 1999, Tom Lane wrote:
>
> > "Brett W. McCoy" <bmccoy@lan2wan.com> writes:
> > >> I have 1,400,000 entries (200MB) I'm inserting into a database.  Radius
> > >> detail files as a matter of fact.  Apart from COPY taking forever to load
> > >> that (probably due to my several indexes), it seems the select is VERY
> > >> slow.  Any tips?
> >
> > > I found that if you create an index before doing a bulk COPY, yes, it does
> > > take forever to load, and the select is slow.  What I did was drop the
> > > indices built from the COPY and rebuild them.  Speeded the selects up
> > > significantly.  So now I don't build any indices until after I load my
> > > huge databases in.
> >
> > Not building the indexes until you've done the bulk load is good advice;
> > it does seem a lot faster to build an index on an already-loaded table
> > than to construct it piecemeal during the COPY.  However, either way
> > should result in the same index, so I don't see why it'd affect the
> > speed of a subsequent SELECT.  Did you remember to do VACUUM ANALYZE
> > both times?  The system is likely to ignore the index until you have
> > vacuumed the table.
> >
> > In short, best bulk load procedure is
> >
> >     CREATE TABLE ...
> >     COPY ...
> >     CREATE INDEX(es) on table
> >     Repeat as needed for all tables being bulk-loaded
> >     VACUUM ANALYZE
> >
> > BTW, if you use pg_dump to dump and reload a big database, pg_dump
> > knows about the create-indexes-last trick.  But it doesn't do a VACUUM
> > for you; you have to do that by hand after running the reload script,
> > or your database will be slow.
> >
> >             regards, tom lane
> >
>
>