PostGIS 1.5.8 Manual - Fedora Project Packages GIT repositories

PostGIS 1.5.8 Manual222 / 310DescriptionThis is a set-returning function (SRF). It returns a set of geometry_dump rows, formed by a geometry (geom) and an array ofintegers (path). When the input geometry is a simple type (POINT,LINESTRING,POLYGON) a single record will be returnedwith an empty path array and the input geometry as geom. When the input geometry is a collection or multi it will return a recordfor each of the collection components, and the path will express the position of the component inside the collection.ST_Dump is useful for expanding geometries. It is the reverse of a GROUP BY in that it creates new rows. For example it canbe use to expand MULTIPOLYGONS into POLYGONS.Availability: PostGIS 1.0.0RC1. Requires PostgreSQL 7.3 or higher.NotePrior to 1.3.4, this function crashes if used with geometries that contain CURVES. This is fixed in 1.3.4+This function supports 3d and will not drop the z-index.This method supports Circular Strings and CurvesExamplesSELECT sometable.field1, sometable.field1,(ST_Dump(sometable.the_geom)).geom AS the_geomFROM sometable;--Break a compound curve into its constituent linestrings and circularstringsSELECT ST_AsEWKT(a.geom), ST_HasArc(a.geom)FROM ( SELECT (ST_Dump(p_geom)).geom AS geomFROM (SELECT ST_GeomFromEWKT(’COMPOUNDCURVE(CIRCULARSTRING(0 0, 1 1, 1 0),(1 0, 01))’) AS p_geom) AS b) AS a;st_asewkt| st_hasarc-----------------------------+----------CIRCULARSTRING(0 0,1 1,1 0) | tLINESTRING(1 0,0 1)| f(2 rows)←↪See Alsogeometry_dump, Section 8.4, ST_Collect, ST_Collect, ST_GeometryN7.9.8 ST_DumpPointsST_DumpPoints — Returns a set of geometry_dump (geom,path) rows of all points that make up a geometry.Synopsisgeometry_dump[]ST_DumpPoints(geometry geom);