[postgis-devel] ST_Expand unexpected behavior

[Obe, Regina]

I'm not really quite sure whether to consider this a bug, but it seems
like unexpected behavior to me.

1) If I expand a 3d box, I get a 3d box back
SELECT ST_Expand(CAST('BOX3D(778783 2951741 1,794875 2970042.61545891
10)' As box3d),10)

yields
BOX3D(778773 2951731 -9,794885 2970052.61545891 20)

2) However if I expand out a 3d geometry, I get back a 2d box. 

SELECT CAST(ST_Expand(ST_GeomFromEWKT('SRID=2163;LINESTRING(2312980
110676 1,2312923 110701 5,2312892 110714 2)'),12) As box3d);

yields
SELECT CAST(ST_Expand(ST_GeomFromEWKT('SRID=2163;LINESTRING(2312980
110676 1,2312923 110701 5,2312892 110714 2)'),12) As box3d);

I understand this is because
I assume we only keep 2d boxes around geometries, but to the casual user
(or at least me with a casual user hat on, its unexpected behavior).

Should I just make a note of this in the docs? I presume there is no
easy fix for this and since our indexes are all 2d, its not all that
useful right now anyway.

Thanks,
Regina

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