From: Warren Young
Date: January 3 2011 11:10am
Subject: Re: Problem with Connection Pointers and Stored Procedures
List-Archive: http://lists.mysql.com/plusplus/9162
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On Jan 3, 2011, at 1:55 AM, Doug Morrow wrote:

> 		std::stringstream ss (std::stringstream::in | =
std::stringstream::out);

It's probably not relevant to your immediate problem, but I can't help =
but wonder, why don't you just use ostringstream here?

> 		mysqlpp::Connection* conn =3D new =
mysqlpp::Connection(false);

[snip]

> 			catch(mysqlpp::Exception e)
> 			{
> 				std::cerr << "mysql++ exception thrown: =
" << e.what() << std::endl;
> 			}


You've disabled exceptions in the Connection creation, so your try block =
does nothing.  You're checking return values as well, which is good =
since exceptions won't be thrown, but you should pick one style or the =
other.

> 		char* qstring =3D new char[256];
> 		ss.getline( qstring, 256 );
> 	=09
> 		std::cout << qstring << std::endl;
> 		if (conn->connect("Somnium", "localhost", "Somnium", =
"password"))
> 		{
> 			mysqlpp::Query query(conn->query((const =
char*)qstring));

Like with stringstream, you're making things hard on yourself here, too. =
 You can get rid of the first two lines (and thus the need to manage =
that bit of memory) and replace the last with:

	mysqlpp::Query query(conn->query(ss.str()));

> 				if(conn->set_option(new =
mysqlpp::MultiStatementsOption(true)))

Your query string doesn't contain multiple SQL queries, so you don't =
need this option.

> 				if(conn->set_option(new =
mysqlpp::MultiResultsOption(true)))
> 							std::cout << =
"MultiResults Set" << std::endl;
> 						else
> 							std::cout << =
"MultiResults NOT Set" << std::endl;

You report that the 'else' doesn't happen, but you should restructure =
your code to make the set_option() call mandatory.  If you can't set the =
multi-results option, the stored procedure call will fail.

> StoredProcedure Call Failed(LookupAccounts): PROCEDURE
> Somnium.LookupAccounts can't return a result set in the given context

I don't really know what that means, but Googling for that error string =
brings me to the MySQL manual:

	http://dev.mysql.com/doc/refman/5.0/en/create-procedure.html

Apparently you're trying to do something in your stored procedure that =
MySQL doesn't support.

> This works fine if I revert the connection object to a static one.

I doubt it.  I modified examples/multiquery.cpp like so, and it works =
just fine:

> Index: examples/multiquery.cpp
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> --- examples/multiquery.cpp	(revision 2683)
> +++ examples/multiquery.cpp	(working copy)
> @@ -145,17 +145,17 @@
>  		// interface.  If you're familiar with the underlying C =
API,
>  		// you know that there is poor consistency on these =
matters;
>  		// MySQL++ abstracts these differences away.
> -		Connection con;
> -		con.set_option(new MultiStatementsOption(true));
> +		Connection* pcon =3D new Connection();
> +		pcon->set_option(new MultiStatementsOption(true));
> =20
>  		// Connect to the database
> -		if (!con.connect(mysqlpp::examples::db_name, =
cmdline.server(),
> +		if (!pcon->connect(mysqlpp::examples::db_name, =
cmdline.server(),
>  				cmdline.user(), cmdline.pass())) {
>  			return 1;
>  		}
> =20
>  		// Set up query with multiple queries.
> -		Query query =3D con.query();
> +		Query query =3D pcon->query();
>  		query << "DROP TABLE IF EXISTS test_table; " <<
>  				"CREATE TABLE test_table(id INT); " <<
>  				"INSERT INTO test_table VALUES(10); " <<
> @@ -187,6 +187,7 @@
>  		cout << "Query: " << query << endl;
>  		print_multiple_results(query);
>  #endif
> +		delete pcon;
> =20
>  		return 0;
>  	}


By the way, I don't see any delete calls for the objects you've created.

It may be that you have a memory bug which is making you believe you =
have this problem with MySQL++.  If you're testing on Linux, try running =
your program under valgrind.  See this FAQ item before reporting errors:

	http://tangentsoft.net/mysql++/#memleak

It may be that changing to ostringstream like I suggested will fix your =
problems, if the issue is that you're overrunning that 256 byte buffer.  =
Letting C++ manage your strings for you solves a lot of problems.=