Subject: Re: Lot'sa joins - performance tip-up, please?
From: Mario Splivalo <msplival@jagor.srce.hr>
To: Dave Dutcher <dave@tridecap.com>,
	pgsql-performance@postgresql.org
In-Reply-To: <003001c66ec5$205a0160$8300a8c0@tridecap.com>
References: <003001c66ec5$205a0160$8300a8c0@tridecap.com>
Content-Type: text/plain
Date: Thu, 04 May 2006 16:15:13 +0200
Message-Id: <1146752113.8538.22.camel@localhost.localdomain>
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On Wed, 2006-05-03 at 10:20 -0500, Dave Dutcher wrote:
> >          ->  Nested Loop  (cost=0.00..176144.30 rows=57925 width=26)
> > (actual time=68.322..529472.026 rows=57925 loops=1)
> >                ->  Seq Scan on ticketing_codes_played
> > (cost=0.00..863.25 rows=57925 width=8) (actual time=0.042..473.881
> > rows=57925 loops=1)
> >                ->  Index Scan using ticketing_codes_pk on
> > ticketing_codes  (cost=0.00..3.01 rows=1 width=18) (actual
> > time=9.102..9.108 rows=1 loops=57925)
> >                      Index Cond: (ticketing_codes.code_id =
> > "outer".code_id)
> >  Total runtime: 542000.093 ms
> > (27 rows)
> > 
> > 
> > I'll be more than happy to provide any additional information 
> > that I may
> > be able to gather. I'd be most happy if someone would scream something
> > like "four joins, smells like a poor design" because design 
> > is poor, but
> > the system is in production, and I have to bare with it.
> 
> 
> It looks like that nested loop which is joining ticketing_codes_played
> to ticketing_codes is the slow part.  I'm curious how many rows are in
> the ticketing_codes table?
> 
> Four or five joins does not seem like a lot to me, but it can be slow if
> you are joining big tables with other big tables.

Ticketing_codes table has 11000000 records, and it's expected to grow.

I tried playing with JOIN order as Tom suggested, but performance is the
same.

	Mario