This topic describes the ST_IsValid function. This function checks whether a geometry object returned by the ST_Geometry function is in a valid format.

Syntax

boolean  ST_IsValid(geometry  g);
boolean  ST_IsValid(geometry  g , integer  flags);

Parameters

Parameter Description
g The geometry object that you want to specify.
flags The bitfield that you want to specify. If you specify this parameter to 1, the self-intersection ring forming a hole is considered to be valid. This is the Environmental Systems Research Institute (ESRI) flag.

Description

If the input geometry object is invalid, this function provides details about the invalid object.

Examples

SELECT ST_IsValid('POLYGON((0 0,0 1,1 0,1 1,0 0))'::geometry);
NOTICE:  Self-intersection at or near point 0.5 0.5
 st_isvalid
------------
 f
(1 row)