From: Mark Kirkwood <markir@paradise.net.nz>
To: list <list@vbp2.vbp2.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: tuning
Date: Tue, 31 May 2005 10:41:59 +1200
Message-ID: <429B96B7.2050502@paradise.net.nz> (raw)
In-Reply-To: <20050526164228.S10655@vbp2.vbp2.com>
References: <20050526164228.S10655@vbp2.vbp2.com>
list wrote:
> hi-
>
> i would like to see if someone could recommend something
> to make my query run faster.
>
>
> Values in postgresql.conf:
> shared_buffers = 1000
> sort_mem is commented out
> effective_cache_size is commented out
> random_page_cost is commented out
>
I would increase shared_buffers (say 5000 - 10000), and also
effective_cache_size (say around 20000 - 50000 - but work out how much
memory this box has free or cached and adjust accordingly).
From your explain output, it looks like sorting is not too much of a
problem - so you can leave it unchanged (for this query anyway).
> Here is the query in question:
> select * from productvendorview where (productlistid=3 or
> productlistid=5 or productlistid=4) and (lower(item) like '9229%' or
> lower(descrip) like 'toner%') order by vendorname,item limit 100;
>
You might want to break this into 2 queries and union them, so you can
(potentially) use the indexes on productlistid,lower(item) and
productlistid, lower(descrip) separately.
> This query scans 412,457 records.
>
> Here is the EXPLAIN ANALYZE for the query:
>
> Limit (cost=45718.83..45719.08 rows=100 width=108) (actual
> time=39093.636..39093.708 rows=100 loops=1)
> -> Sort (cost=45718.83..45727.48 rows=3458 width=108) (actual
> time=39093.629..39093.655 rows=100 loops=1)
> Sort Key: v.vendorname, p.item
> -> Hash Join (cost=22.50..45515.57 rows=3458 width=108)
> (actual time=95.490..39062.927 rows=2440 loops=1)
> Hash Cond: ("outer".vendorid = "inner".id)
> -> Seq Scan on test p (cost=0.00..45432.57 rows=3457
> width=62) (actual time=89.066..39041.654 rows=2444 loops=1)
> Filter: (((productlistid = 3) OR (productlistid =
> 5) OR (productlistid = 4)) AND
> ((lower((item)::text) ~~ '9229%'::text) OR
> (lower((descrip)::text) ~~ 'toner%'::text)))
> -> Hash (cost=20.00..20.00 rows=1000 width=54) (actual
> time=6.289..6.289 rows=0 loops=1)
> -> Seq Scan on vendor v (cost=0.00..20.00
> rows=1000 width=54) (actual time=0.060..3.653 rows=2797 loops=1)
> Total runtime: 39094.713 ms
> (10 rows)
>
I guess the relation 'test' is a copy of product (?)
Cheers
Mark
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To: pgsql-performance@postgresql.org
Cc: markir@paradise.net.nz, list@vbp2.vbp2.com
Subject: Re: tuning
In-Reply-To: <429B96B7.2050502@paradise.net.nz>
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