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I have records stored in a table with latitude/longitude coordinates stored in a geometry field. I want to find all records nearby a user supplied reference point. Note "nearby" probably means less than 100km (possibly even smaller).

Most examples I see use ST_DWithin. Is there a reason you can't use ST_Distance? What is the difference between using ST_DWithin and ST_Distance to do this?

For example:

SELECT name, ST_AsText(coords)
FROM places
WHERE ST_DWithin(coords, ST_GeomFromText('POINT(-12.5842 24.4944)',4326), 1)

vs

SELECT name, ST_AsText(coords)
FROM places
WHERE ST_Distance(coords, ST_GeomFromText('POINT(-12.5842 24.4944)',4326)) < 1
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1 Answer 1

up vote 6 down vote accepted

ST_Distance is a calculation which must be executed and evaluated on every row. ST_DWithin can use an index, so it's likely to be much faster.

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Also managed to find this which says pretty much same thing: postgis.net/2013/08/26/tip_ST_DWithin –  User Dec 10 '13 at 5:45

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