Paris Code Sprint 2016 : PostGIS Agenda

Discussion and group review topics for the Paris Code Sprint 2016.
== Discussion ==
* Clustering functions: Aggregate or Window?
** What naming convention
** What to do with the existing aggregate functions
* Expanded object headers, introduction and testing
** How they work
** Potential advantages, disadvantages
** Discussion on clean implementation possibilities
** Testing and benchmarks, is it worth it?
* Alternate storage formats, beyond GSERIALIZED
** Reasoning
** How to add (version flags?)
** Multiple co-existing formats?
* Breaking raster out as postgis_raster extension (hold off on talking about this until Regina comes)
** Implications / difficulties
* GEOS improvements that would help PostGIS
* Way to know/be sure a geometry is valid, without need to launch an IsValid test (SFCGAL initial purpose)
* Using FDW with PostGIS (hold off on talking about this until Regina comes)
** Functions pushdown
** Current limitations
* PostgreSQL improvements that would help PostGIS
** Parallel query, review experiments, plan and execute more (hold off on talking about this until Regina comes)
** Feed back parallel query results to pgsql-hackers
* Open pull requests from GitHub
** Merge, modify, or reject
* Tickets with design implications
** https://trac.osgeo.org/postgis/ticket/2529
** https://trac.osgeo.org/postgis/ticket/3405
** https://trac.osgeo.org/postgis/ticket/3246
** https://trac.osgeo.org/postgis/ticket/3326
* Do we want to bundle example datasets w/PostGIS for docs, tutorials?
* Adding more checks to automated builds?
** valgrind (would need to add suppressions for GEOS leaks)
** gcov (identify untested or unused code paths)
== Tasks ==
* Benchmarking of expanded object headers test branch
* Benchmarking of parallel query and parallel aggregate work from pgsql-hackers
* BRIN indexes implementation for PostGIS geometries
* postgis/lwgeom_in_* move to liblwgeom dir (or any code that doesn't depend on Postgres?)
== Possible PostGIS function improvement and addition ==
* improvement
** st_pointN -> make a negative input count backward [rémi]
** st_setPoint -> make a negative input count backward [rémi]
** st_asText -> optionnal arg to limit digit number [marc]
** st_centroid -> work on circular string (simply dump points, then classical centroid) [remi] 
** st_exteriorRing -> make it work on multipolygon, returns a collection
** st_makeline -> make it work on multipoints [pauln]
** st_scale -> optionnal argument to define the center of scaling (allows to scale "in place") [marc]
** st_split -> allow splitting (multi)line by (multi)point
** st_asgml -> allow GML 3.2.1 support (not only namespace handle) http://portal.opengeospatial.org/files/?artifact_id=26765
** st_asgml (and st_geomfromgml) -> handle gml:Envelope
** ST_AsX3D -> Bug fix - how to determine if 3D geometry is convex without resorting to CGAL. http://trac.osgeo.org/postgis/ticket/3435 [regina]
** ST_GeogFromText -> make the longitude swap 180 deg when entering a latitude over 90 (postgis already counts the latitude backwards from 90 when crossing) [manu]
* slight addition
** st_angle(P1,P2,P3) [remi]
** st_MakeRing((multi) linestrings and/or points
** st_DumpLines -> dump everything to line (rings in poly, lines in multilines, etc. )
** st_DumpSegments -> dump segments (in the mathematical sense), that is every consecutive pairs of points in lines
* big addition
** generate grid (regular and hex)
** st_snapToLine -> st_snap = snap vertex to vertex. This one = snap vertex to vertex or edge. (note: st_snap also snap line to vertex)
** st_splitLineByPoint(line,point,tolerance) -> using curv absc, the only current way to not be sensible to precision issue (st_split doesnt work)
** st_VariableBuffer(geomM) -> buffer on geometry, the radius is given by M of each vertex, linear transition between. A lots of uses
** St_FindCurve(geom,radius_range,min_number_of_support_points,tolerance) -> in a classical geometry, find the point describing arcs
** St_MakeArc(P1,P2,centre) and St_MakeArc(P1,P2,radius) -> create arcs (_not_ using 3 points on arc!)
** St_OrientedBBox(geom) -> returns the oriented bbox of the geom (returns a geom and an angle)
** ST_KMeans -> window function - pramsey to integrate into 2.3 code base - https://github.com/pramsey/postgis/tree/kmeans