Spatial: Translate aggregate functions

[bricelam]

There are a handful of aggregate functions for spatial data. (Collect, Extent, Union, etc.)

It would be nice if we had a way to represent them in LINQ.

.NET	SQL Server	SpatiaLite	PostGIS
EnvelopeCombiner.Combine(geoms)	EnvelopeAggregate(@​geoms)	Extent(@​geoms)	ST_Extent(@​geoms)
GeometryCombiner.Combine(geoms)	CollectionAggregate(@​geoms)	Collect(@​geoms)	ST_Collect(@​geoms)
UnaryUnionOp.Union(geoms)	UnionAggregate(@​geoms)	GUnion(@​geoms)	ST_Union(@​geoms)
ConvexHull.Create(geoms)	ConvexHullAggregate(@​geoms)	ST_ConvexHull(Collect(@​geoms))	ST_ConvexHull(ST_Collect(@​geoms))

[bricelam]

See also NetTopologySuite/NetTopologySuite#246

[roji]

As this is being proposed for 6.0, would we build more generic support for arbitrary aggregate functions? There's #11850 but that seems to be about DbFunctions - do we need a separate issue to track provider aggregate functions?

/cc @smitpatel

[smitpatel]

This is being proposed for 6.0? 😕

[roji]

Yeah, #22951...

[roji]

(a separate issue for tracking arbitrary non-DbFunction aggregate functions support may be a good idea regardless of 6.0, unless we just want to use #11850 to track that too)

[smitpatel]

arbitrary non-DbFunction aggregate functions support

They are already supported. 🤷

[roji]

Oh, nice!

[roji]

Specifically for plugins (NTS), note that we don't have an extension point for QueryableMethodTranslatingExpressionVisitor, which is needed if we want to support top-level invocations of aggregate functions (similar to Max/Sum/Average).