Datum SPI_getbinval(HeapTuple row, TupleDesc rowdesc, int colnumber, bool * isnull)
SPI_getbinval returns the value of the specified column in the internal form (as type Datum).
This function does not allocate new space for the datum. In the case of a pass-by-reference data type, the return value will be a pointer into the passed row.
The binary value of the column is returned. The variable pointed to by isnull is set to true if the column is null, else to false.
SPI_result is set to SPI_ERROR_NOATTRIBUTE on error.