[postgis-tickets] [PostGIS] #3889: Support --without-geos switch

[PostGIS]

#3889: Support --without-geos switch
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 Reporter:  robe     |      Owner:  pramsey
     Type:  defect   |     Status:  new
 Priority:  medium   |  Milestone:  PostGIS 2.5.0
Component:  postgis  |    Version:  trunk
 Keywords:           |
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 This was a request from Darafei Praliaskouski (Komzpa) made on IRC on
 behalf of Postgres Professional (https://postgrespro.com/)

 Normally I'd laugh at such a request, but I'd like to do it for a couple
 of reasons especially if Komzpa is willing to put in the sweat to make it
 happen.

 1. Postgres Professional (is lead by Oleg Bartunov and Teodor Sigaev)
 which many long standing folks in PostGIS community might recognize as the
 faces behind GiST (which makes PostGIS so fast) and  Full-Text search in
 addition to index improvements on JSON.

 2.  They need it for a very good cause. They need a lighter-weight PostGIS
 that can be used easily in conjunction with GEOS, so they can defend the
 security of it to the Russian Government.

 GEOS is too big of a creature for them to audit and approve.

 3. I forsee this as an easy way for new developers to get up to speed
 contributing to PostGIS since the requirements to compile will be lower.

 My proposal is as follows.

 If postgis is compiled --without-geos  (we assume if that config is not
 present then we still require geos), much like we do --without-raster,
 then all GEOS functions will be stubbed and throw an error, something like


 {{{
 Requires GEOS, you need to recompile your PostGIS with GEOS support to use
 this function
 }}}

 4. However the following function ST_Intersects will still be available,
 but instead of using GEOS would piggy back on _ST_DWithin, much like what
 geography type does already.  We'll should do  this on the C-side so no
 upgrading needs to be done if people recompile / --without-geos  or with
 geos.

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Ticket URL: <https://trac.osgeo.org/postgis/ticket/3889>
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