geometry-expression.ST_WithinFilter(geo2)

The ST_WithinFilter method provides an efficient test to determine if one geometry might be within the other. Returns 1 if the geometry-expression might be within geo2, otherwise 0.

This test is cheaper than ST_Within, but may return 1 in some cases where the geometry-expression is not actually spatially within geo2.

Therefore, this method can be useful as a primary filter when further processing will determine if geometries interact in the desired way.

The implementation of ST_WithinFilter relies upon meta-data associated with the stored geometries. Because the available meta-data may change between server versions, depending upon how the data is loaded, or where ST_WithinFilter is used within a query, the expression geometry-expression.ST_WithinFilter(geo2) can return different results when geometry-expression is not within geo2. Whenever geometry-expression is within geo2, ST_WithinFilter will always return 1.

• ST_Within method for type ST_Geometry