Returns a geometry representing the index hash.
      Syntax
         
            ST_Geometry::ST_LinearUnHash(BINARY(32) index_hash[, INT srid])
      
      Parameters
         
            - 
               index_hash – 
               The index hash string.
            
- 
               srid – 
               The SRID of the index hash. If not specified, the default is 0.
            
Returns
         ST_Geometry Returns a representative geometry for the given linear hash.
      Standards
         
            SQL/MM (ISO/IEC 13249-3: 2006) Vendor extension