src/test/examples/testlibpq2.c

   1 /*
   2  * src/test/examples/testlibpq2.c
   3  *
   4  *
   5  * testlibpq2.c
   6  *              Test of the asynchronous notification interface
   7  *
   8  * Start this program, then from psql in another window do
   9  *       NOTIFY TBL2;
  10  * Repeat four times to get this program to exit.
  11  *
  12  * Or, if you want to get fancy, try this:
  13  * populate a database with the following commands
  14  * (provided in src/test/examples/testlibpq2.sql):
  15  *
  16  *       CREATE SCHEMA TESTLIBPQ2;
  17  *       SET search_path = TESTLIBPQ2;
  18  *       CREATE TABLE TBL1 (i int4);
  19  *       CREATE TABLE TBL2 (i int4);
  20  *       CREATE RULE r1 AS ON INSERT TO TBL1 DO
  21  *         (INSERT INTO TBL2 VALUES (new.i); NOTIFY TBL2);
  22  *
  23  * Start this program, then from psql do this four times:
  24  *
  25  *       INSERT INTO TESTLIBPQ2.TBL1 VALUES (10);
  26  */
  27
  28 #ifdef WIN32
  29 #include <windows.h>
  30 #endif
  31 #include <stdio.h>
  32 #include <stdlib.h>
  33 #include <string.h>
  34 #include <errno.h>
  35 #include <sys/select.h>
  36 #include <sys/time.h>
  37 #include <sys/types.h>
  38
  39 #include "libpq-fe.h"
  40
  41 static void
  42 exit_nicely(PGconn *conn)
  43 {
  44         PQfinish(conn);
  45         exit(1);
  46 }
  47
  48 int
  49 main(int argc, char **argv)
  50 {
  51         const char *conninfo;
  52         PGconn     *conn;
  53         PGresult   *res;
  54         PGnotify   *notify;
  55         int                     nnotifies;
  56
  57         /*
  58          * If the user supplies a parameter on the command line, use it as the
  59          * conninfo string; otherwise default to setting dbname=postgres and using
  60          * environment variables or defaults for all other connection parameters.
  61          */
  62         if (argc > 1)
  63                 conninfo = argv[1];
  64         else
  65                 conninfo = "dbname = postgres";
  66
  67         /* Make a connection to the database */
  68         conn = PQconnectdb(conninfo);
  69
  70         /* Check to see that the backend connection was successfully made */
  71         if (PQstatus(conn) != CONNECTION_OK)
  72         {
  73                 fprintf(stderr, "%s", PQerrorMessage(conn));
  74                 exit_nicely(conn);
  75         }
  76
  77         /* Set always-secure search path, so malicious users can't take control. */
  78         res = PQexec(conn,
  79                                  "SELECT pg_catalog.set_config('search_path', '', false)");
  80         if (PQresultStatus(res) != PGRES_TUPLES_OK)
  81         {
  82                 fprintf(stderr, "SET failed: %s", PQerrorMessage(conn));
  83                 PQclear(res);
  84                 exit_nicely(conn);
  85         }
  86
  87         /*
  88          * Should PQclear PGresult whenever it is no longer needed to avoid memory
  89          * leaks
  90          */
  91         PQclear(res);
  92
  93         /*
  94          * Issue LISTEN command to enable notifications from the rule's NOTIFY.
  95          */
  96         res = PQexec(conn, "LISTEN TBL2");
  97         if (PQresultStatus(res) != PGRES_COMMAND_OK)
  98         {
  99                 fprintf(stderr, "LISTEN command failed: %s", PQerrorMessage(conn));
 100                 PQclear(res);
 101                 exit_nicely(conn);
 102         }
 103         PQclear(res);
 104
 105         /* Quit after four notifies are received. */
 106         nnotifies = 0;
 107         while (nnotifies < 4)
 108         {
 109                 /*
 110                  * Sleep until something happens on the connection.  We use select(2)
 111                  * to wait for input, but you could also use poll() or similar
 112                  * facilities.
 113                  */
 114                 int                     sock;
 115                 fd_set          input_mask;
 116
 117                 sock = PQsocket(conn);
 118
 119                 if (sock < 0)
 120                         break;                          /* shouldn't happen */
 121
 122                 FD_ZERO(&input_mask);
 123                 FD_SET(sock, &input_mask);
 124
 125                 if (select(sock + 1, &input_mask, NULL, NULL, NULL) < 0)
 126                 {
 127                         fprintf(stderr, "select() failed: %s\n", strerror(errno));
 128                         exit_nicely(conn);
 129                 }
 130
 131                 /* Now check for input */
 132                 PQconsumeInput(conn);
 133                 while ((notify = PQnotifies(conn)) != NULL)
 134                 {
 135                         fprintf(stderr,
 136                                         "ASYNC NOTIFY of '%s' received from backend PID %d\n",
 137                                         notify->relname, notify->be_pid);
 138                         PQfreemem(notify);
 139                         nnotifies++;
 140                         PQconsumeInput(conn);
 141                 }
 142         }
 143
 144         fprintf(stderr, "Done.\n");
 145
 146         /* close the connection to the database and cleanup */
 147         PQfinish(conn);
 148
 149         return 0;
 150 }