Message-ID: <453636F1.7000903@freesurf.fr>
Date: Wed, 18 Oct 2006 16:15:13 +0200
From: Arnaud Lesauvage <thewild@freesurf.fr>
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To: Heikki Linnakangas <heikki@enterprisedb.com>
CC: pgsql-performance@postgresql.org
Subject: Re: Index on two columns not used
References: <45360E25.9010403@freesurf.fr> <45361295.9050504@enterprisedb.com>
	<45361A2D.6080702@freesurf.fr> <453632C5.50501@enterprisedb.com>
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Heikki Linnakangas a écrit :
> Arnaud Lesauvage wrote:
>> This query was taken from my "adminsitrative areas" model (continents, 
>> countries, etc...). Whenever I query this model, I have to join many 
>> tables.
>> I don't really know what the overhead of reading the heap-tuples is, but 
>> would it be a good idea to add data-redundancy in my tables to avoid 
>> joins ? (adding country_id, continent_id, etc... in the "cities" table)
> 
> It depends. I would advise not to denormalize unless you really really 
> have to. It's hard to say without more knowledge of the application.
> 
> Is the query you showed a typical one? It ran in about 160 ms, is that 
> good enough? It's doesn't sound too bad, considering that it returned 
> almost 40000 rows.


It is quite typical, yes. It is the base query of a view. In 
fact, most views have a lot more joins (they join with all 
the upper-level tables).
But 150ms is OK, indeed.