PostgreSQL provides a fast-path interface to send function calls to the backend. This is a trapdoor into system internals and can be a potential security hole. Most users will not need this feature.
PQfn
Request execution of a
backend function via the fast-path interface.
PGresult* PQfn(PGconn* conn, int fnid, int *result_buf, int *result_len, int result_is_int, const PQArgBlock *args, int nargs);
The fnid
argument is the
object identifier of the function to be executed.
result_buf
is the buffer in
which to place the return value. The caller must have
allocated sufficient space to store the return value (there
is no check!). The actual result length will be returned in
the integer pointed to by result_len
. If a 4-byte integer result is
expected, set result_is_int
to
1; otherwise set it to 0. (Setting result_is_int
to 1 tells libpq to byte-swap the value if
necessary, so that it is delivered as a proper int value for
the client machine. When result_is_int
is 0, the byte string sent
by the backend is returned unmodified.) args
and nargs
specify the arguments to be passed
to the function.
typedef struct { int len; int isint; union { int *ptr; int integer; } u; } PQArgBlock;
PQfn
always returns a valid
PGresult*. The resultStatus
should be checked before the result is used. The caller is
responsible for freeing the PGresult with PQclear
when it is no longer needed.