[postgis-users] BBOX coordinates and GiST

[Bernhard Reimar Hoefle]

Hi!
I do want to use the GiST index for Points and Multipoints. As it works on
BBoxes, the BBoxes should be as small as possible.

If I'm right BBox coordinates are stored as float4. For large coordinates, such
as 3212345611.34 the box coordinates are rounded/cut? to 3212345600.00. I guess
that this behaviour cannot be changed because my coordinates have always more
than 8 digits and therefore BBoxes in the spatial index overlap?

But why do I get different results, already using small/reduced coordinates, for
POINT and MULTIPOINT objects?

Do I have to change the BBOXCACHE_BEHAVIOURS, if I want exact BBoxes, also for
MULTIPOINTs?

Example:

POINT(-2.730 -5.679 536.27) | BOX(-2.73000001907349 -5.68000030517578,-2.7299997
8065491 -5.67999982833862)

MULTIPOINT(-4.5599999986589 -6.08999999985099 552.17,-1.92000000178814
-4.12000000011176 536.28) | BOX(-6 -6.5,0 -4)

Thanks,
Bernhard