Paris Code Sprint 2016 : PostGIS Agenda

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Discussion and group review topics for the Paris Code Sprint 2016.


  • 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
  • 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)


  • 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)
    • st_asgml (and st_geomfromgml) -> handle gml:Envelope
    • ST_AsX3D -> Bug fix - how to determine if 3D geometry is convex without resorting to CGAL. [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 -