geometry-expression.ST_LinearHash()

The spatial index support uses a linear hash for geometries that maps the geometries in a table into a linear order in a B-Tree index. The ST_LinearHash method exposes this mapping by returning a binary string that gives the ordering of the rows in the B-Tree index. The hash string provides the following property: if geometry A covers geometry B, then A.ST_LinearHash() >= B.ST_LinearHash().

The linear hash can be used in an ORDER BY clause. For example, when unloading data from a SELECT statement, ST_LinearHash can be used to generate a data file that matches the clustering of a spatial index.

• ST_LinearUnHash method for type ST_Geometry