src/test/examples/testlibpq4.c

   1 /*
   2  * $PostgreSQL:$
   3  *
   4  *
   5  * testlibpq4.c
   6  *              this test program shows to use LIBPQ to make multiple backend
   7  * connections
   8  *
   9  */
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include "libpq-fe.h"
  13
  14 static void
  15 exit_nicely(PGconn *conn1, PGconn *conn2)
  16 {
  17         if (conn1)
  18                 PQfinish(conn1);
  19         if (conn2)
  20                 PQfinish(conn2);
  21         exit(1);
  22 }
  23
  24 static void
  25 check_conn(PGconn *conn, const char *dbName)
  26 {
  27         /* check to see that the backend connection was successfully made */
  28         if (PQstatus(conn) != CONNECTION_OK)
  29         {
  30                 fprintf(stderr, "Connection to database \"%s\" failed: %s",
  31                                 dbName, PQerrorMessage(conn));
  32                 exit(1);
  33         }
  34 }
  35
  36 int
  37 main(int argc, char **argv)
  38 {
  39         char       *pghost,
  40                            *pgport,
  41                            *pgoptions,
  42                            *pgtty;
  43         char       *dbName1,
  44                            *dbName2;
  45         char       *tblName;
  46         int                     nFields;
  47         int                     i,
  48                                 j;
  49
  50         PGconn     *conn1,
  51                            *conn2;
  52
  53         /*
  54          * PGresult   *res1, *res2;
  55          */
  56         PGresult   *res1;
  57
  58         if (argc != 4)
  59         {
  60                 fprintf(stderr, "usage: %s tableName dbName1 dbName2\n", argv[0]);
  61                 fprintf(stderr, "      compares two tables in two databases\n");
  62                 exit(1);
  63         }
  64         tblName = argv[1];
  65         dbName1 = argv[2];
  66         dbName2 = argv[3];
  67
  68
  69         /*
  70          * begin, by setting the parameters for a backend connection if the
  71          * parameters are null, then the system will try to use reasonable
  72          * defaults by looking up environment variables or, failing that, using
  73          * hardwired constants
  74          */
  75         pghost = NULL;                          /* host name of the backend server */
  76         pgport = NULL;                          /* port of the backend server */
  77         pgoptions = NULL;                       /* special options to start up the backend
  78                                                                  * server */
  79         pgtty = NULL;                           /* debugging tty for the backend server */
  80
  81         /* make a connection to the database */
  82         conn1 = PQsetdb(pghost, pgport, pgoptions, pgtty, dbName1);
  83         check_conn(conn1, dbName1);
  84
  85         conn2 = PQsetdb(pghost, pgport, pgoptions, pgtty, dbName2);
  86         check_conn(conn2, dbName2);
  87
  88         /* start a transaction block */
  89         res1 = PQexec(conn1, "BEGIN");
  90         if (PQresultStatus(res1) != PGRES_COMMAND_OK)
  91         {
  92                 fprintf(stderr, "BEGIN command failed\n");
  93                 PQclear(res1);
  94                 exit_nicely(conn1, conn2);
  95         }
  96
  97         /*
  98          * make sure to PQclear() a PGresult whenever it is no longer needed to
  99          * avoid memory leaks
 100          */
 101         PQclear(res1);
 102
 103         /*
 104          * fetch instances from the pg_database, the system catalog of databases
 105          */
 106         res1 = PQexec(conn1, "DECLARE myportal CURSOR FOR select * from pg_database");
 107         if (PQresultStatus(res1) != PGRES_COMMAND_OK)
 108         {
 109                 fprintf(stderr, "DECLARE CURSOR command failed\n");
 110                 PQclear(res1);
 111                 exit_nicely(conn1, conn2);
 112         }
 113         PQclear(res1);
 114
 115         res1 = PQexec(conn1, "FETCH ALL in myportal");
 116         if (PQresultStatus(res1) != PGRES_TUPLES_OK)
 117         {
 118                 fprintf(stderr, "FETCH ALL command didn't return tuples properly\n");
 119                 PQclear(res1);
 120                 exit_nicely(conn1, conn2);
 121         }
 122
 123         /* first, print out the attribute names */
 124         nFields = PQnfields(res1);
 125         for (i = 0; i < nFields; i++)
 126                 printf("%-15s", PQfname(res1, i));
 127         printf("\n\n");
 128
 129         /* next, print out the instances */
 130         for (i = 0; i < PQntuples(res1); i++)
 131         {
 132                 for (j = 0; j < nFields; j++)
 133                         printf("%-15s", PQgetvalue(res1, i, j));
 134                 printf("\n");
 135         }
 136
 137         PQclear(res1);
 138
 139         /* close the portal */
 140         res1 = PQexec(conn1, "CLOSE myportal");
 141         PQclear(res1);
 142
 143         /* end the transaction */
 144         res1 = PQexec(conn1, "END");
 145         PQclear(res1);
 146
 147         /* close the connections to the database and cleanup */
 148         PQfinish(conn1);
 149         PQfinish(conn2);
 150
 151 /*       fclose(debug); */
 152         return 0;
 153 }