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58cd8dca3d
libpq's error messages for connection failures pretty well stand on their own, especially since commits 52a10224e/27a48e5a1. Prefixing them with 'could not connect to database "foo"' or the like is just redundant, and perhaps even misleading if the specific database name isn't relevant to the failure. (When it is, we trust that the backend's error message will include the DB name.) Indeed, psql hasn't used any such prefix in a long time. So, make all our other programs and documentation examples agree with psql's practice. Discussion: https://postgr.es/m/1094524.1611266589@sss.pgh.pa.us
132 lines
2.9 KiB
C
132 lines
2.9 KiB
C
/*
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* src/test/examples/testlibpq.c
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*
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*
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* testlibpq.c
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*
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* Test the C version of libpq, the PostgreSQL frontend library.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include "libpq-fe.h"
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static void
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exit_nicely(PGconn *conn)
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{
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PQfinish(conn);
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exit(1);
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}
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int
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main(int argc, char **argv)
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{
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const char *conninfo;
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PGconn *conn;
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PGresult *res;
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int nFields;
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int i,
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j;
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/*
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* If the user supplies a parameter on the command line, use it as the
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* conninfo string; otherwise default to setting dbname=postgres and using
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* environment variables or defaults for all other connection parameters.
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*/
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if (argc > 1)
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conninfo = argv[1];
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else
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conninfo = "dbname = postgres";
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/* Make a connection to the database */
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conn = PQconnectdb(conninfo);
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/* Check to see that the backend connection was successfully made */
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if (PQstatus(conn) != CONNECTION_OK)
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{
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fprintf(stderr, "%s", PQerrorMessage(conn));
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exit_nicely(conn);
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}
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/* Set always-secure search path, so malicious users can't take control. */
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res = PQexec(conn,
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"SELECT pg_catalog.set_config('search_path', '', false)");
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if (PQresultStatus(res) != PGRES_TUPLES_OK)
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{
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fprintf(stderr, "SET failed: %s", PQerrorMessage(conn));
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PQclear(res);
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exit_nicely(conn);
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}
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/*
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* Should PQclear PGresult whenever it is no longer needed to avoid memory
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* leaks
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*/
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PQclear(res);
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/*
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* Our test case here involves using a cursor, for which we must be inside
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* a transaction block. We could do the whole thing with a single
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* PQexec() of "select * from pg_database", but that's too trivial to make
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* a good example.
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*/
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/* Start a transaction block */
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res = PQexec(conn, "BEGIN");
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if (PQresultStatus(res) != PGRES_COMMAND_OK)
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{
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fprintf(stderr, "BEGIN command failed: %s", PQerrorMessage(conn));
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PQclear(res);
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exit_nicely(conn);
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}
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PQclear(res);
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/*
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* Fetch rows from pg_database, the system catalog of databases
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*/
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res = PQexec(conn, "DECLARE myportal CURSOR FOR select * from pg_database");
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if (PQresultStatus(res) != PGRES_COMMAND_OK)
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{
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fprintf(stderr, "DECLARE CURSOR failed: %s", PQerrorMessage(conn));
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PQclear(res);
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exit_nicely(conn);
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}
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PQclear(res);
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res = PQexec(conn, "FETCH ALL in myportal");
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if (PQresultStatus(res) != PGRES_TUPLES_OK)
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{
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fprintf(stderr, "FETCH ALL failed: %s", PQerrorMessage(conn));
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PQclear(res);
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exit_nicely(conn);
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}
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/* first, print out the attribute names */
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nFields = PQnfields(res);
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for (i = 0; i < nFields; i++)
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printf("%-15s", PQfname(res, i));
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printf("\n\n");
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/* next, print out the rows */
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for (i = 0; i < PQntuples(res); i++)
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{
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for (j = 0; j < nFields; j++)
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printf("%-15s", PQgetvalue(res, i, j));
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printf("\n");
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}
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PQclear(res);
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/* close the portal ... we don't bother to check for errors ... */
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res = PQexec(conn, "CLOSE myportal");
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PQclear(res);
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/* end the transaction */
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res = PQexec(conn, "END");
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PQclear(res);
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/* close the connection to the database and cleanup */
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PQfinish(conn);
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return 0;
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}
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