Description

The VALIDPOLYGONFROMTEXT() function generates a valid GEOGRAPHY value from a string containing a well known text (WKT) representation of a geographic polygon. If the GEOGRAPHY value resulting from the WKT string cannot be made into a valid representation of a polygon, the function returns an error. The error message includes an explanation of why the WKT is not valid. If the polygon is valid except the rings are drawn in the wrong direction (that is, the outer ring is clockwise or the inner rings are counterclockwise), the VALIDPOLYGONFROMTEXT() function will correct the rings and generate a valid polygon.

The difference between the POLYGONFROMTEXT() function and the VALIDPOLYGONFROMTEXT() function is that the VALIDPOLYGONFROMTEXT() verifies that the resulting polygon meets all of the requirements for use by VoltDB. If a valid polygon cannot be generated, the VALIDPOLYGONFROMTEXT() function returns an error. The POLYGONFROMTEXT() function, on the other hand, simply constructs a GEOGRAPHY value without validating all of the requirements of a VoltDB polygon and may need separate validation (using the ISVALID() or MAKEVALIDPOLYGON() function) before it can be used effectively with other geospatial functions. See the description of the ISVALID() function for a description of the requirements for a valid polygon.

Example

The following example uses the VALIDPOLYGONFROMTEXT() function to insert a record containing a GEOGRAPHY column using a text input value containing the WKT representation of a geographic polygon. Note that if

INSERT INTO city (name, state, boundary) 
    VALUES(?, ?, VALIDPOLYGONFROMTEXT(?));