SPI_getargtypeid returns the OID representing the type id for the argIndex'th argument of a plan prepared by SPI_prepare. First argument is at index zero.
execution plan (returned by SPI_prepare)
zero based index of the argument
The type id of the argument at the given index, or SPI_ERROR_ARGUMENT if the plan is NULL or argIndex is less than 0 or not less than the number of arguments declared for the plan
