notify problem

[Alessandro GARDICH]

Hi to all

I have problem with NOTIFY/LISTEN ...
I'm writing a C++ application with libpqxx, I thought was a problem of
the lib but I try also with a C program using libpq with the same
result, so maybe there is something else of wrong.

Using the example 2 in the libpq chapter on "Postgres Programmer's
Guide" as template i write :

!---------->
#include <unistd.h>
#include <libpq-fe.h>

int main() {

PGconn *conn;
PGresult *res;
PGnotify *notify;

int i;

conn = PQconnectdb ("host=localhos t user=test dbname=test");

if (PQstatus(conn) == CONNECTION_BAD) {
fprintf(stderr, "failed connecting.\n") ;
PQfinish(conn);
exit(1);
}

res = PQexec(conn, "LISTEN alert");
if (!res || PQresultStatus( res) != PGRES_COMMAND_O K) {
fprintf(stderr, "failed listening.\n");
PQclear(res);
PQfinish(conn);
exit(1);
}

PQclear(res);

for(i = 0; i < 80 ; ++i) {
sleep(1);
PQconsumeInput( conn);
while ((notify = PQnotifies(conn )) != NULL) {
fprintf(stderr, "\nGOT NOTIFY!!!\n");
free(notify);
}
fprintf(stderr, ".");
}

PQfinish(conn);

return 0;
}
<----------!
On a console with psql I issue some notify with
NOTIFY alert; COMMIT;

but nothing are catched !!!

if in another console with psql i do a "LISTEN alert;" all work
correctly.

I'm using Linux, RedHat 9, so PostgreSQL 7.3.2.
user and database are created with :
createuser -h localhost -U postgres -D -A -P test
createdb -O test -h localhost -U postgres test

and nothing alse, the database are empty.

what's wrong ???

Thanks.
--
Alessandro GARDICH <gr*****@gremli n.it>
gremlin.it

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[Tom Lane]

Alessandro GARDICH <gr*****@gremli n.it> writes:

res = PQexec(conn, "LISTEN alert"); for(i = 0; i < 80 ; ++i) {
sleep(1);
PQconsumeInput( conn);
while ((notify = PQnotifies(conn )) != NULL) {
fprintf(stderr, "\nGOT NOTIFY!!!\n");
free(notify);
}
fprintf(stderr, ".");
} On a console with psql I issue some notify with
NOTIFY alert; COMMIT;
but nothing are catched !!!

Hm. Should I guess from the above that you've set autocommit off in
postgresql.conf ? If so, your problem is you didn't commit the LISTEN.
Notifications are not sent to clients that are in open transactions.

regards, tom lane

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