libpq-fe: how to determine unique collision ?

Hi,

I am using libpq (with postgreSQL Version: 6.5.3-23 (Debian 2.2r2)). I
have the following questions which, I am afraid, are not answered in the
documentation:

- how do you detect the error `Can't insert tuple because duplicate' ?

- how do you get the OID of an insertion (the goal being to get
the value for the SERIAL type, in order to do something with it) ?

Thank you.

Example:
CREATE TABLE file (id SERIAL,
creation_time TIMESTAMP
NOT NULL DEFAULT CURRENT_TIMESTAMP,
last_access_time TIMESTAMP, /* read some data */
file_name VARCHAR(100) NOT NULL, /* see servers_defs.h */
client_name VARCHAR(30) NOT NULL, /* from auth */
server_name VARCHAR(30) NOT NULL, /* from auth */
UNIQUE(client_name, server_name, file_name),
UNIQUE(id), PRIMARY KEY(id));

#include "libpq-fe.h"

#define BUFFER_LENGTH 1024 /* Is boundary-checked */
BOOL db_create_file_tuple(db_context_t context,
const char *file_name,
const char *client_name,
const char *server_name,
db_error_t *error) {
char buffer[BUFFER_LENGTH];
BOOL result = FALSE;
PGconn *conn = (PGconn *) context;

*error = DB_ERROR_INTERNAL;

if (snprintf(buffer,
sizeof(buffer),
"INSERT INTO file (file_name, client_name, server_name)"
" VALUES('%s', '%s', '%s')",
file_name,
client_name,
server_name)
== -1) {
*error = DB_ERROR_WOULD_OVERFLOW;
}
else {
PGresult *res;

/* BUGS
* - Should protect or bind like in Perl.
*/

res = PQexec(conn, buffer);
if (res && (PQresultStatus(res) == PGRES_COMMAND_OK)) {
result = TRUE;
*error = DB_ERROR_NONE; /* not really useful, shouldn't be read */
}
else {
debug_log(DEBUG_LEVEL_ERROR,
"INSERT query failed: %s",
PQerrorMessage(conn));

/* BUGS
* - We are not sure this is it, but we can only guess
* for now.
*/
*error = DB_ERROR_FILE_OBJECT_EXISTS;
}

PQclear(res); /* avoid memory leaks */
}

return result;
}