Use of spatial functions in a query

A spatial index is used as a consideration in certain queries.

The Db2 optimizer considers a spatial index for use when a query contains one the following functions in its WHERE clause:

• ST_Contains
• ST_Crosses
• ST_Distance
• EnvelopesIntersect
• ST_Equals
• ST_Intersects
• ST_Overlaps
• ST_Touches
• ST_Within

In addition, the expression to the right of the predicate must be equal to 1, except when ST_Distance is the function on the left. With the ST_Distance function, the predicate must be less than the numeric value that is on the right.