[raster] speed up ST_Envelope

[strk]

I noticed that ST_Envelope(rast) is implemented as ST_Envelope(ST_ConvexHull(rast)).

I'm not sure if that's necessary. Ideally ST_Envelope should be able to give a response by only looking at the raster header, without even fully detoasting the raster.

See #2822

[dustymugs]

ST_ConvexHull() is only detoasting the header. But the issue is that convexhull generates a geometry to generate a envelope geometry, an unnecessary step.

[robe]

don't have the code in front of me but I recall the actual case rast::geometry implemented with ST_ConvexHull(rast)?

[strk]

Yes, the cast to geometry is implemented as ST_ConvexHull(rast)

[dustymugs]

Fixed in trunk as of r12832

[strk]

Did you forget to add a test for rt_envelope ? r12832 adds a reference to such test in raster/test/regress/Makefile.in but there's no such new test file.

[dustymugs]

Oops. Forgot to add the files to git. Fixed as of r12859