[postgis-users] How to get the centroid of an bounding box using st_extent

[Charlie Savage]

It turns out that st_extent is hundreds of times faster than Envelope. 
But I run into a problem when using it:

select st_extent('POINT(10 10)')
"BOX(10 10,10 10)"

But if you do this:

select asText(centroid(st_extent('POINT(10 10)')))
"GEOMETRYCOLLECTION EMPTY"


Which is the same issue I mentioned a couple weeks ago where 
Envelope('POINT(10 10)') doesn't return a point like it should.

So I'd like to use st_extent, but a need a way to get a valid point that 
represents the center of the bounds instead of an empty collection.  How?

Charlie
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