src/test/examples/testlibpq.c

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * $PostgreSQL: pgsql/src/test/examples/testlibpq.c,v 1.18 2009/06/11 14:49:15 momjian Exp $
 *
 *
 * testlibpq.c
 *
 *		Test the C version of libpq, the PostgreSQL frontend library.
 */
#include <stdio.h>
#include <stdlib.h>
#include "libpq-fe.h"

static void
exit_nicely(PGconn *conn)
{
	PQfinish(conn);
	exit(1);
}

int
main(int argc, char **argv)
{
	const char *conninfo;
	PGconn	   *conn;
	PGresult   *res;
	int			nFields;
	int			i,
				j;

	/*
	 * If the user supplies a parameter on the command line, use it as the
	 * conninfo string; otherwise default to setting dbname=postgres and using
	 * environment variables or defaults for all other connection parameters.
	 */
	if (argc > 1)
		conninfo = argv[1];
	else
		conninfo = "dbname = postgres";

	/* Make a connection to the database */
	conn = PQconnectdb(conninfo);

	/* Check to see that the backend connection was successfully made */
	if (PQstatus(conn) != CONNECTION_OK)
	{
		fprintf(stderr, "Connection to database failed: %s",
				PQerrorMessage(conn));
		exit_nicely(conn);
	}

	/*
	 * Our test case here involves using a cursor, for which we must be inside
	 * a transaction block.  We could do the whole thing with a single
	 * PQexec() of "select * from pg_database", but that's too trivial to make
	 * a good example.
	 */

	/* Start a transaction block */
	res = PQexec(conn, "BEGIN");
	if (PQresultStatus(res) != PGRES_COMMAND_OK)
	{
		fprintf(stderr, "BEGIN command failed: %s", PQerrorMessage(conn));
		PQclear(res);
		exit_nicely(conn);
	}

	/*
	 * Should PQclear PGresult whenever it is no longer needed to avoid memory
	 * leaks
	 */
	PQclear(res);

	/*
	 * Fetch rows from pg_database, the system catalog of databases
	 */
	res = PQexec(conn, "DECLARE myportal CURSOR FOR select * from pg_database");
	if (PQresultStatus(res) != PGRES_COMMAND_OK)
	{
		fprintf(stderr, "DECLARE CURSOR failed: %s", PQerrorMessage(conn));
		PQclear(res);
		exit_nicely(conn);
	}
	PQclear(res);

	res = PQexec(conn, "FETCH ALL in myportal");
	if (PQresultStatus(res) != PGRES_TUPLES_OK)
	{
		fprintf(stderr, "FETCH ALL failed: %s", PQerrorMessage(conn));
		PQclear(res);
		exit_nicely(conn);
	}

	/* first, print out the attribute names */
	nFields = PQnfields(res);
	for (i = 0; i < nFields; i++)
		printf("%-15s", PQfname(res, i));
	printf("\n\n");

	/* next, print out the rows */
	for (i = 0; i < PQntuples(res); i++)
	{
		for (j = 0; j < nFields; j++)
			printf("%-15s", PQgetvalue(res, i, j));
		printf("\n");
	}

	PQclear(res);

	/* close the portal ... we don't bother to check for errors ... */
	res = PQexec(conn, "CLOSE myportal");
	PQclear(res);

	/* end the transaction */
	res = PQexec(conn, "END");
	PQclear(res);

	/* close the connection to the database and cleanup */
	PQfinish(conn);

	return 0;
}