From: | "Jonathan Raemdonck" <jonathan_raemdonck(at)hotmail(dot)com> |
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To: | pgsql-general(at)postgresql(dot)org |
Subject: | indexing lat lon |
Date: | 2004-06-27 22:40:32 |
Message-ID: | BAY17-F18cc4zyjKILk0004498b@hotmail.com |
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Thread: | |
Lists: | pgsql-general |
I have the following situation:
I'm developing an reverse geocoder, so input is lat/lon coordinate and
output is the nearest textual location.
I have a database of +- 2 000 000 records that contains lat/lon and full
name of the location.
These are the steps I take now:
1 'draw' a box around the lat/lon position we have as input
2 search the DB for all the points in this box
3 measure the distance to each point in the box
This works fine, but step 2 takes too lang for obvious reasons...
select * from table
where lat between box_point1_lat and box_point2_lat
and lon between box_point1_lon and box_point2_lon;
This would require a seq scan for but indexing the table doesn't help much
either (factor 2) ...
Is there a good way of indexing the lat/lon column so lookup is faster? I
have looked at PostGis but didn't think it would give a good solution in
this context (correct me if I'm wrong)
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