The data type of each value in a column ColumnType(column)
The attribute value will be one of AST__INTTYPE (for integer), AST__SINTTYPE (for short int), AST__BYTETYPE (for unsigned bytes - i.e. unsigned chars), AST__DOUBLETYPE (for double precision floating point), AST__FLOATTYPE (for single precision floating point), AST__STRINGTYPE (for character string), AST__OBJECTTYPE (for AST Object pointer), AST__POINTERTYPE (for arbitrary C pointer) or AST__UNDEFTYPE (for undefined values created by astMapPutU).