Postgres95 1.01 Distribution - Virgin Sources

src/test/examples/testlibpq2.c

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+/*
+ * 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);
+
+ *
+ *
+ */
+#include <stdio.h>
+#include "libpq-fe.h"
+
+void exit_nicely(PGconn* conn)
+{
+  PQfinish(conn);
+  exit(1);
+}
+
+main()
+{
+  char *pghost, *pgport, *pgoptions, *pgtty;
+  char* dbName;
+  int nFields;
+  int i,j;
+
+  PGconn* conn;
+  PGresult* res;
+  PGnotify* notify;
+
+  /* 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 */
+  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*/
+
+  /* make a connection to the database */
+  conn = PQsetdb(pghost, pgport, pgoptions, pgtty, dbName);
+
+  /* check to see that the backend connection was successfully made */
+  if (PQstatus(conn) == CONNECTION_BAD) {
+    fprintf(stderr,"Connection to database '%s' failed.\n", dbName);
+    fprintf(stderr,"%s",PQerrorMessage(conn));
+    exit_nicely(conn);
+  }
+
+  res = PQexec(conn, "LISTEN TBL2");
+  if (PQresultStatus(res) != PGRES_COMMAND_OK) {
+    fprintf(stderr,"LISTEN command failed\n");
+    PQclear(res);
+    exit_nicely(conn);
+  }
+  /* should PQclear PGresult whenever it is no longer needed to avoid
+     memory leaks */
+  PQclear(res); 
+
+  while (1) {
+      /* async notification only come back as a result of a query*/
+      /* we can send empty queries */
+      res = PQexec(conn, " ");
+/*      printf("res->status = %s\n", pgresStatus[PQresultStatus(res)]); */
+      /* check for asynchronous returns */
+      notify = PQnotifies(conn);
+      if (notify) {
+	  fprintf(stderr,
+		  "ASYNC NOTIFY of '%s' from backend pid '%d' received\n",
+		  notify->relname, notify->be_pid);
+	  free(notify);
+	  break;
+      }
+      PQclear(res);
+  }
+      
+  /* close the connection to the database and cleanup */
+  PQfinish(conn);
+
+}
+  
+