testlibpq.c

关系型数据库 Postgresql 6.5.2

/*
 * testlibpq.c
 *		Test the C version of LIBPQ, the POSTGRES frontend library.
 *
 *
 */
#include <stdio.h>
#include "libpq-fe.h"

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

int
main()
{
	char	   *pghost,
			   *pgport,
			   *pgoptions,
			   *pgtty;
	char	   *dbName;
	int			nFields;
	int			i,
				j;

#ifdef DEBUG
	FILE	   *debug;

#endif	 /* DEBUG */

	PGconn	   *conn;
	PGresult   *res;

	/*
	 * begin, by setting the parameters for a backend connection if the
	 * parameters are null, then the system will try to use reasonable
	 * defaults by looking up environment variables or, failing that,
	 * using hardwired constants
	 */
	pghost = NULL;				/* host name of the backend server */
	pgport = NULL;				/* port of the backend server */
	pgoptions = NULL;			/* special options to start up the backend
								 * server */
	pgtty = NULL;				/* debugging tty for the backend server */
	dbName = "template1";

	/* make a connection to the database */
	conn = PQsetdb(pghost, pgport, pgoptions, pgtty, dbName);

	/* check to see that the backend connection was successfully made */
	if (PQstatus(conn) == CONNECTION_BAD)
	{
		fprintf(stderr, "Connection to database '%s' failed.\n", dbName);
		fprintf(stderr, "%s", PQerrorMessage(conn));
		exit_nicely(conn);
	}

#ifdef DEBUG
	debug = fopen("/tmp/trace.out", "w");
	PQtrace(conn, debug);
#endif	 /* DEBUG */

	/* start a transaction block */
	res = PQexec(conn, "BEGIN");
	if (PQresultStatus(res) != PGRES_COMMAND_OK)
	{
		fprintf(stderr, "BEGIN command failed\n");
		PQclear(res);
		exit_nicely(conn);
	}

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

	/*
	 * fetch instances from the 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 command failed\n");
		PQclear(res);
		exit_nicely(conn);
	}
	PQclear(res);

	res = PQexec(conn, "FETCH ALL in myportal");
	if (PQresultStatus(res) != PGRES_TUPLES_OK)
	{
		fprintf(stderr, "FETCH ALL command didn't return tuples properly\n");
		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 instances */
	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 */
	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);

#ifdef DEBUG
	fclose(debug);
#endif	 /* DEBUG */

	exit(0);
}