ST_MMin and ST_MMax functions for geometry

[mwtoews]

This is a feature request for ST_MMin and ST_MMax functions, to complement similar existing functions for X, Y and Z dimensions, but to be applied to the M dimension.

[strk]

The thing is that while X/Y min/max are available as part of the bounding box I dunno if we have M (and Z) there. Unless we know have multidimensional box in the header. Do we, Paul ?

[pramsey]

For geometries with Z and M coordinates the header boxes are populated with those extrema that you would expect. For geographies the boxes are actually the geocentric boxes, so the header boxes aren't what you'd expect.

[robe]

strk,

We already have a ST_ZMin, ST_ZMax for box3d. Does box3d even have a slot for M? pramsey are you saying it does?

Just in case it's not obvious: NONE of these functions we have are defined for geometry/geography and are ONLY defined for box3d. Even the X one ​http://postgis.net/docs/manual-dev/ST_XMin.html. We chucked the box2d variants a long time ago.

They work for geometry cause we have an implicit cast to box3d for geometry. We have no such thing for geography so these functions have NEVER (not even ST_XMin) worked for geography without casting to geometry first.

[robe]

Milestone renamed