Allow passing per-dimension parameters in ST_Expand

[strk]

Allow ST_Expand to take one amount for each dimension:

ST_Expand(geometry, x float8, y float8, z float8, m float8);

The current function would keep using the same amount for all of them.

[dbaston]

This seems like a nice way to improve hackish ST_DWithin queries on WGS84 geometries stored as geometry.

So, to find polygons within 1km of a point, you could do:

SELECT * FROM polygons
WHERE geom && ST_Expand('POINT (37 52)', 1000.0/69000, 1000.0/111111, 0.0)
AND ST_Distance_Sphere(geom, 'POINT (37 52)') < 1000

where 69000 m approximates 1 degree of longitude, and 111111 m approximates 1 degree of latitude (at 52 degrees N)

[strk]

I'm so glad we have you on board Daniel :)

[robe]

I'm so glad too you are on board Dan, but I must scold you for using ST_Distance_Sphere instead of ST_DistanceSphere. ​http://postgis.net/docs/manual-2.2/ST_DistanceSphere.html

I'm surprised strk didn't pick up on that since he's the pedantic one.

[dbaston]

Thanks all, and sorry if I occasionally get nostalgic for a comfortable, well-aged function name from a simpler time.

[dbaston]

Committed to trunk at r14929 / r14930