NTS: Additional translations

[bricelam]

Doing my research, I found some additional translations you may want to add:

NTS	PostGIS
AsBinary	ST_AsBinary
Buffer	ST_Buffer
ConvexHull	ST_ConvexHull
Dimension	ST_Dimension
EndPoint	ST_EndPoint
Envelope	ST_Envelope
ExteriorRing	ST_ExteriorRing
GetInteriorRingN	ST_InteriorRingN
GetPointN	ST_PointN
IsCCW	ST_IsPolygonCCW
IsRing	ST_IsRing
Normalized	ST_Normalize
NumInteriorRings	ST_NumInteriorRing
PointOnSurface	ST_PointOnSurface
SRID	ST_SRID
StartPoint	ST_StartPoint
ToGMLFeature	ST_AsGML
WKBReader.Read	ST_GeomFromWKB
WKTReader.Read	ST_GeomFromText

[roji]

Yeah, went I implemented the NTS plugin I implemented everything that was straightforward. The above were more difficult for some reason - mainly because the NetTopologySuite API didn't map out-of-the-box - so I deferred them. As people request the above we'll work on adding them.

This is a good up-for-grabs for anyone wanting to get some practice on EF Core SQL translation - I'll accept PRs for individual translations (you don't have to do everything at once).

[tematim]

Hello,

I'll need these one too :
Point
ST_Equals
ST_Buffer

LineString
ST_Centroid
ST_StartPoint
ST_Equals
ST_Buffer

Polygon
ST_Centroid
ST_Multi
ST_Buffer
ST_Dump

[slavanap]

Please don't forget about ST_GeographyFromWKT. I really need that one. Now I'm trying to use NetTopologySuite.Geometries.Geometry.DefaultFactory.CreateMultiPolygon() as a workaround.

[slavanap]

More than that, I'm trying to migrate to PostGIS from SqlGeography and haven't found method similar to SqlGeography.ReorientObject() just yet.

[roji]

Note, implemented the following as part of #672: ST_Dimension, ST_EndPoint, ST_Envelope, ST_ExteriorRing, ST_IsRing, ST_NumInteriorRings, ST_PointOnSurface, ST_SRID, ST_StartPoint

[EricStG]

Are there plans to add the <-> operator to that list? while Distance would work, it doesn't use indexes

[roji]

@EricStG am far from a PostGIS expert: should the <-> operator be used everywhere instead of ST_Distance? If so, why does ST_Distance exist and not make use of indexes? Any more precise info on this would help.

[EricStG]

@roji I'm far from being an expert as well, but my understanding is that <-> returns values that gives you relative distances, but doesn't necessarily map to a real distance unit, that's why it only makes sense to use it for ordering.
From this section, they mention that only specific functions/operators can make use of indices, but not sure why this couldn't be applied to something like ST_Distance

[roji]

@EricStG thanks for the extra info, although I'm still not totally clear on what should happen, and when exactly <-> should be used instead of ST_Distance().

Can you help out by contacting the PostGIS folks and asking for clarification, possibly proposing that they make their documentation clearer on this point?

[EricStG]

To get the nearest neighbors, you would use <->
To search within a distance, you would use ST_DWithin. More info here: https://postgis.net/2013/08/26/tip_ST_DWithin/

You would use ST_Distance or ST_Distance_Sphere when you need to know the actual distance between two points. like the kilometers between two geography points, but because it's calculated for every row, performance would suffer over any significant datasets.

I'll try posting on the PostGIS mailing list to see if anyone can point me to better documentation.