How to use use_spheroid=false in ST_DWithin?

Question

I have created 2 geography columns and indexed them using `GIST`. I am looking to use `ST_DWithin` for a larger dataset and to make it faster trying to use the `use_spheroid=false`. SELECT pois.objectid, ST_Multi(ST_Union(polygon.coordinates)) as coords into table3 FROM table1 as polygon INNER JOIN table12 as pois ON ST_DWithin(polygon.geog,pois.geog, 10* 1609.34, use_spheroid=false) group by pois.objectid    limit 1; but I get the following error, ERROR: column "use_spheroid" does not exist I feel that I am not using the `use_spheroid=false` argument correctly. Could you please help me?

Answer 1

You are correct to consider using use_spheroid=false for optimizing performance, especially with large datasets and ST_DWithin. The problem is with how you're passing the parameter.

If you are working with geography in PostGIS, you should use the 3-argument version of ST_DWithin with the use_spheroid option; if you want to specify use_spheroid, you should use the 4-argument version.

You have a syntax error, though, because use_spheroid=false is a positional argument in the function call rather than a named parameter in SQL.

Here’s the correct usage:

ST_DWithin(geog1, geog2, distance, false)

So your query should look like this:

SELECT

pois.objectid,

ST_Multi(ST_Union(polygon.coordinates)) as coords

INTO table3

FROM table1 as polygon

INNER JOIN table12 as pois

ON ST_DWithin(polygon.geog, pois.geog, 10 * 1609.34, false)

GROUP BY pois.objectid

LIMIT 1;

That false is the use_spheroid flag in the 4-argument version of ST_DWithin.