[postgis-tickets] [PostGIS] #3853: datum slicing for bounding box retrieval is busted

[PostGIS]

#3853: datum slicing for bounding box retrieval is busted
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 Reporter:  pramsey      |      Owner:  pramsey
     Type:  enhancement  |     Status:  new
 Priority:  medium       |  Milestone:  PostGIS 2.4.0
Component:  postgis      |    Version:  trunk
 Keywords:               |
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 I found that for points/short lines, the box retrieval functions were
 double-detoasting every time:

 * first a slice to pull a box off the slice
 * the points have no box so second we detoast the whole thing

 The idea of slicing is for large objects to avoid an expensive detoast
 just to get the box, but...

 * postgis uses "storage = main"
 * and main storage has a policy to first compress, then use external toast
 tables

 so we are usually going to end up with compressed values in main tables.

 But... that means that slicing never works, since the first step in
 slicing is "decompress the whole thing". At that point we might as well
 just have the thing back and get to work, the slice gains us nothing.

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Ticket URL: <https://trac.osgeo.org/postgis/ticket/3853>
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