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,
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.