[Re]introduce postgis_geos_noop() and postgis_sfcgal_noop()

[lucasvr]

PostGIS used to expose a SQL function named geosnoop(geometry) to test the cost of deserializing and reserializing from the PostgreSQL backend. The attached patch brings that function back (this time named as postgis_geos_noop(geometry)) together with its SFCGAL counterpart (postgis_sfcgal_noop(geometry)).

[strk]

Can you please also add tests under regress/ directory ? What i get is:

strk=# select st_npoints(postgis_sfcgal_noop(ST_Buffer('POINT(0 0)', 5)));
ERROR:  Unknown geometry type: 8208 - Invalid type

Other function (geos) is fine.

For tests I see also postgis_noop testing is missing, you could add that one in regress/regress.sql togheter with the postgis_geos_noop, and the geos_sfcgal_noop would go in regress_sfcgal.sql

[strk]

for the bug itself it sounds like due to the fact you're not re-serializing the output (geometry_serialize)

[robe]

Has to go in 2.5 since it adds to SQL API.

[lucasvr]

It looks like I've attached the first diff that I produced for review purposes. Sorry about that, it was indeed missing the re-serializing part!

I have submitted a new patch (v2) that includes the re-serializing and the regression tests. I've also updated the comments to reflect that this API is available from 2.5.0 onwards. I appreciate your review and guidance on missing bits (if any).

Thanks!

[lucasvr]

Revamped version of the original patch

[strk]

Sounds good. Only thing is (beside a missing TAB on line 792 of postgis/lwgeom_sfcgal.c) is I'd avoid the Buffer call in the test and give the geos_noop test a good label like the sfcgal one.

If you feel like doing more, ideally those noop tests would test not a single geometry but a range of geometry types and dimensions, ensuring for example that the SRID is retained upon round-trip and the Z value (GEOS does not support the M value, not sure about sfcgal, if it does it's worth testing that too) and the different types (not all types are supported by GEOS)

[strk]

postgis_geos_noop was added, see #2902, so this ticket remains for postgis_sfcgal_noop. Are you willing to complete the patch to include in 3.0.0 lucasvr ?

[komzpa]

In 17727:

postgis_sfcgal_noop().

Patch by Lucas C. Villa Real <lucasvr@…>, tweaks by Darafei Praliaskouski

Closes #3979