SPI_fnumber - Man Page

int SPI_fnumber(TupleDesc rowdesc, const char * colname)

SPI_fnumber returns the column number for the column with the specified name.

If colname refers to a system column (e.g., ctid) then the appropriate negative column number will be returned. The caller should be careful to test the return value for exact equality to SPI_ERROR_NOATTRIBUTE to detect an error; testing the result for less than or equal to 0 is not correct unless system columns should be rejected.

TupleDesc rowdesc

const char * colname

Column number (count starts at 1 for user-defined columns), or SPI_ERROR_NOATTRIBUTE if the named column was not found.