Reconstructing PostGIS geometry from ST_DumpPoints()?

Question

The PostGIS ST_DumpPoints function seems to have enough data in the return value about the structure of geometries (in the path field):

It returns a set of geometry_dump rows, each containing a geometry (geom field) and an array of integers (path field).

• the geom field POINTs represent the coordinates of the supplied geometry.

• the path field (an integer[]) is an index enumerating the coordinate positions in the elements of the supplied geometry. The indices are 1-based. For example, for a LINESTRING the paths are {i} where i is the nth coordinate in the LINESTRING. For a POLYGON the paths are {i,j} where i is the ring number (1 is outer; inner rings follow) and j is the coordinate position in the ring.

Is there a function in PostGIS to reconstruct a specific type of geometry (e.g. MULTIPOLYGON, or LINESTRING) from its point dump table to get back the original geometry?

(I know ST_MakeLine, but I was wondering if there is a more general inverse of ST_Dump type functions.)

Answer 1

No.

You will have to manually aggregate the dumped Point geometries according to their index and unique (row) identifier, and in a dimensional bottom-up fashion - and you will need n-1 aggregation steps for n elements in the returned path array, to reconstruct the original geometry.