geometry_dump — A spatial datatype with two fields - geom (holding a geometry object) and path[] (a 1-d array holding the position of the geometry within the dumped object.)
geometry_dump is a compound data type consisting of a geometry object referenced by the .geom field and path[] a 1-dimensional integer array (starting at 1 e.g. path[1] to get first element) array that defines the navigation path within the dumped geometry to find this element. It is used by the ST_Dump* family of functions as an output type to explode a more complex geometry into its constituent parts and location of parts.