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Indexing on a circle datatype

From: Gavin Love <gavin(at)splicer(dot)org(dot)uk>
To: pgsql-performance(at)postgresql(dot)org
Subject: Indexing on a circle datatype
Date: 2009-08-24 16:27:49
Message-ID: 4A92BF85.7070507@splicer.org.uk (view raw or flat)
Thread:
Lists: pgsql-performance
Hey,

I seem to be unable to get postgres to use a gist index we have on a 
circle data type.

Table "public.tradesmen_profiles"
       Column         |            Type             |       Modifiers    
-----------------------+-----------------------------+----------------------- 

id                          | integer                     | not null
work_area             | circle                       |
Indexes:
   "tradesmen_profiles_pkey" PRIMARY KEY, btree (id)
    "tradesmen_profiles_test" gist (work_area)

We are then trying to do the following query

SELECT  id FROM  tradesmen_profiles WHERE tradesmen_profiles.work_area  
@> point(0.0548691728419,51.5404384172);

Which produces the following:

QUERY PLAN                                                     
----------------------------------------------------------------------------------------------------------------------- 

Seq Scan on tradesmen_profiles  (cost=0.00..3403.55 rows=14942 width=4) 
(actual time=0.042..31.427 rows=5898 loops=1)
  Filter: (work_area @> '(0.0548691728419,51.5404384172)'::point)
Total runtime: 39.556 ms

I have also vacuum'd  and reindexed the table after building the index

VACUUM ANALYZE VERBOSE tradesmen_profiles;
REINDEX TABLE tradesmen_profiles;

So am I just trying to do something that is not possible or have I just 
made a mistake with what I am trying to do?
This is not a big problem just now but as our data set grows I am 
worried that having to do a sequence scan on this table every time will 
be a serious performance overhead.

Thanks for your help,

Gavin

Responses

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Next:From: Matthew WakelingDate: 2009-08-24 17:03:48
Subject: Re: Indexing on a circle datatype
Previous:From: Kevin GrittnerDate: 2009-08-24 14:45:42
Subject: Re: improving my query plan

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