Ticket #1535 (closed defect: fixed)
Negative distance argument to ST_Buffer not documented
|Reported by:||rutsky||Owned by:||robe|
Documentation to ST_Buffer  says that argument "radius_of_buffer" is distance and defines buffer operation as "all points whose distance from this Geometry/geography is less than or equal to distance".
Documentation implies that ST_Buffer can buffer only on positive values which isn't correct as I see in practice, and since ST_Buffer is implemented using GEOS it is possible to buffer on negative distances .