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testlibpq2.c
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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/time.h>
36 #include <sys/types.h>
37 #ifdef HAVE_SYS_SELECT_H
38 #include <sys/select.h>
39 #endif
40 
41 #include "libpq-fe.h"
42 
43 static void
45 {
46  PQfinish(conn);
47  exit(1);
48 }
49 
50 int
51 main(int argc, char **argv)
52 {
53  const char *conninfo;
54  PGconn *conn;
55  PGresult *res;
56  PGnotify *notify;
57  int nnotifies;
58 
59  /*
60  * If the user supplies a parameter on the command line, use it as the
61  * conninfo string; otherwise default to setting dbname=postgres and using
62  * environment variables or defaults for all other connection parameters.
63  */
64  if (argc > 1)
65  conninfo = argv[1];
66  else
67  conninfo = "dbname = postgres";
68 
69  /* Make a connection to the database */
70  conn = PQconnectdb(conninfo);
71 
72  /* Check to see that the backend connection was successfully made */
73  if (PQstatus(conn) != CONNECTION_OK)
74  {
75  fprintf(stderr, "Connection to database failed: %s",
76  PQerrorMessage(conn));
77  exit_nicely(conn);
78  }
79 
80  /* Set always-secure search path, so malicous users can't take control. */
81  res = PQexec(conn,
82  "SELECT pg_catalog.set_config('search_path', '', false)");
83  if (PQresultStatus(res) != PGRES_COMMAND_OK)
84  {
85  fprintf(stderr, "SET failed: %s", PQerrorMessage(conn));
86  PQclear(res);
87  exit_nicely(conn);
88  }
89 
90  /*
91  * Should PQclear PGresult whenever it is no longer needed to avoid memory
92  * leaks
93  */
94  PQclear(res);
95 
96  /*
97  * Issue LISTEN command to enable notifications from the rule's NOTIFY.
98  */
99  res = PQexec(conn, "LISTEN TBL2");
100  if (PQresultStatus(res) != PGRES_COMMAND_OK)
101  {
102  fprintf(stderr, "LISTEN command failed: %s", PQerrorMessage(conn));
103  PQclear(res);
104  exit_nicely(conn);
105  }
106  PQclear(res);
107 
108  /* Quit after four notifies are received. */
109  nnotifies = 0;
110  while (nnotifies < 4)
111  {
112  /*
113  * Sleep until something happens on the connection. We use select(2)
114  * to wait for input, but you could also use poll() or similar
115  * facilities.
116  */
117  int sock;
118  fd_set input_mask;
119 
120  sock = PQsocket(conn);
121 
122  if (sock < 0)
123  break; /* shouldn't happen */
124 
125  FD_ZERO(&input_mask);
126  FD_SET(sock, &input_mask);
127 
128  if (select(sock + 1, &input_mask, NULL, NULL, NULL) < 0)
129  {
130  fprintf(stderr, "select() failed: %s\n", strerror(errno));
131  exit_nicely(conn);
132  }
133 
134  /* Now check for input */
135  PQconsumeInput(conn);
136  while ((notify = PQnotifies(conn)) != NULL)
137  {
138  fprintf(stderr,
139  "ASYNC NOTIFY of '%s' received from backend PID %d\n",
140  notify->relname, notify->be_pid);
141  PQfreemem(notify);
142  nnotifies++;
143  }
144  }
145 
146  fprintf(stderr, "Done.\n");
147 
148  /* close the connection to the database and cleanup */
149  PQfinish(conn);
150 
151  return 0;
152 }
char * PQerrorMessage(const PGconn *conn)
Definition: fe-connect.c:6116
PGnotify * PQnotifies(PGconn *conn)
Definition: fe-exec.c:2244
void PQfinish(PGconn *conn)
Definition: fe-connect.c:3638
ExecStatusType PQresultStatus(const PGresult *res)
Definition: fe-exec.c:2647
PGconn * conn
Definition: streamutil.c:55
int be_pid
Definition: libpq-fe.h:164
int main(int argc, char **argv)
Definition: testlibpq2.c:51
#define select(n, r, w, e, timeout)
Definition: win32_port.h:447
char * relname
Definition: libpq-fe.h:163
int PQconsumeInput(PGconn *conn)
Definition: fe-exec.c:1682
void PQclear(PGresult *res)
Definition: fe-exec.c:671
static void exit_nicely(PGconn *conn)
Definition: testlibpq2.c:44
const char * strerror(int errnum)
Definition: strerror.c:19
PGresult * PQexec(PGconn *conn, const char *query)
Definition: fe-exec.c:1897
ConnStatusType PQstatus(const PGconn *conn)
Definition: fe-connect.c:6063
void PQfreemem(void *ptr)
Definition: fe-exec.c:3251
int PQsocket(const PGconn *conn)
Definition: fe-connect.c:6134
PGconn * PQconnectdb(const char *conninfo)
Definition: fe-connect.c:592