Bring the libpq example programs into the 21st century.

src/test/examples/testlibpq2.c

@@ -2,24 +2,30 @@
  * testlibpq2.c
  *		Test of the asynchronous notification interface
  *
-   populate a database with the following:
-
-CREATE TABLE TBL1 (i int4);
-
-CREATE TABLE TBL2 (i int4);
-
-CREATE RULE r1 AS ON INSERT TO TBL1 DO [INSERT INTO TBL2 values (new.i); NOTIFY TBL2];
-
- * Then start up this program
- * After the program has begun, do
-
-INSERT INTO TBL1 values (10);
-
+ * Start this program, then from psql in another window do
+ *   NOTIFY TBL2;
+ * Repeat four times to get this program to exit.
  *
+ * Or, if you want to get fancy, try this:
+ * populate a database with the following commands
+ * (provided in src/test/examples/testlibpq2.sql):
  *
+ *   CREATE TABLE TBL1 (i int4);
+ *
+ *   CREATE TABLE TBL2 (i int4);
+ *
+ *   CREATE RULE r1 AS ON INSERT TO TBL1 DO
+ *     (INSERT INTO TBL2 VALUES (new.i); NOTIFY TBL2);
+ *
+ * and do this four times:
+ *
+ *   INSERT INTO TBL1 VALUES (10);
  */
 #include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <sys/time.h>
 #include "libpq-fe.h"
 
 static void
@@ -30,51 +36,43 @@ exit_nicely(PGconn *conn)
 }
 
 int
-main()
+main(int argc, char **argv)
 {
-	char	   *pghost,
-			   *pgport,
-			   *pgoptions,
-			   *pgtty;
-	char	   *dbName;
-
-	/*
-	 * int			nFields; int		  i, j;
-	 */
-
+	const char *conninfo;
 	PGconn	   *conn;
 	PGresult   *res;
 	PGnotify   *notify;
+	int			nnotifies;
 
 	/*
-	 * begin, by setting the parameters for a backend connection if the
-	 * parameters are null, then the system will try to use reasonable
-	 * defaults by looking up environment variables or, failing that,
-	 * using hardwired constants
+	 * If the user supplies a parameter on the command line, use it as
+	 * the conninfo string; otherwise default to setting dbname=template1
+	 * and using environment variables or defaults for all other connection
+	 * parameters.
 	 */
-	pghost = NULL;				/* host name of the backend server */
-	pgport = NULL;				/* port of the backend server */
-	pgoptions = NULL;			/* special options to start up the backend
-								 * server */
-	pgtty = NULL;				/* debugging tty for the backend server */
-	dbName = getenv("USER");	/* change this to the name of your test
-								 * database */
+	if (argc > 1)
+		conninfo = argv[1];
+	else
+		conninfo = "dbname = template1";
 
-	/* make a connection to the database */
-	conn = PQsetdb(pghost, pgport, pgoptions, pgtty, dbName);
+	/* Make a connection to the database */
+	conn = PQconnectdb(conninfo);
 
-	/* check to see that the backend connection was successfully made */
-	if (PQstatus(conn) == CONNECTION_BAD)
+	/* Check to see that the backend connection was successfully made */
+	if (PQstatus(conn) != CONNECTION_OK)
 	{
-		fprintf(stderr, "Connection to database '%s' failed.\n", dbName);
+		fprintf(stderr, "Connection to database '%s' failed.\n", PQdb(conn));
 		fprintf(stderr, "%s", PQerrorMessage(conn));
 		exit_nicely(conn);
 	}
 
+	/*
+	 * Issue LISTEN command to enable notifications from the rule's NOTIFY.
+	 */
 	res = PQexec(conn, "LISTEN TBL2");
 	if (PQresultStatus(res) != PGRES_COMMAND_OK)
 	{
-		fprintf(stderr, "LISTEN command failed\n");
+		fprintf(stderr, "LISTEN command failed: %s", PQerrorMessage(conn));
 		PQclear(res);
 		exit_nicely(conn);
 	}
@@ -85,27 +83,48 @@ main()
 	 */
 	PQclear(res);
 
-	while (1)
+	/* Quit after four notifies are received. */
+	nnotifies = 0;
+	while (nnotifies < 4)
 	{
-		/* async notification only come back as a result of a query */
-		/* we can send empty queries */
-		res = PQexec(conn, " ");
-/*		printf("res->status = %s\n", PQresStatus(PQresultStatus(res))); */
-		/* check for asynchronous returns */
-		notify = PQnotifies(conn);
-		if (notify)
+		/*
+		 * Sleep until something happens on the connection.  We use select(2)
+		 * to wait for input, but you could also use poll() or similar
+		 * facilities.
+		 */
+		int			sock;
+		fd_set		input_mask;
+
+		sock = PQsocket(conn);
+
+		if (sock < 0)
+			break;				/* shouldn't happen */
+
+		FD_ZERO(&input_mask);
+		FD_SET(sock, &input_mask);
+
+		if (select(sock + 1, &input_mask, NULL, NULL, NULL) < 0)
+		{
+			fprintf(stderr, "select() failed: %s\n", strerror(errno));
+			exit_nicely(conn);
+		}
+
+		/* Now check for input */
+		PQconsumeInput(conn);
+		while ((notify = PQnotifies(conn)) != NULL)
 		{
 			fprintf(stderr,
-				 "ASYNC NOTIFY of '%s' from backend pid '%d' received\n",
+					"ASYNC NOTIFY of '%s' received from backend pid %d\n",
 					notify->relname, notify->be_pid);
 			PQfreemem(notify);
-			break;
+			nnotifies++;
 		}
-		PQclear(res);
 	}
 
+	fprintf(stderr, "Done.\n");
+
 	/* close the connection to the database and cleanup */
 	PQfinish(conn);
-	return 0;					/* Though PQfinish(conn1) has called
-								 * exit(1) */
+
+	return 0;
 }