SPI_fnumber — determine the column number for the specified column name
int SPI_fnumber(TupleDescrowdesc, 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.,
oid) 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 rowdescinput row description
const char * colnamecolumn name
Column number (count starts at 1 for user-defined columns), or
SPI_ERROR_NOATTRIBUTE if the named column was not
found.