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Re: BUG #5268: PQgetvalue incorrectly returns 0

From:	Mike Landis <mlandis(at)pnmx(dot)com>
To:	pgsql-bugs(at)postgresql(dot)org
Subject:	Re: BUG #5268: PQgetvalue incorrectly returns 0
Date:	2010-01-07 12:51:54
Message-ID:	20100107125237.0CF58632AE0@mail.postgresql.org
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<body>
Try the following, where
mystring is an extension of std::string... 
mystring sql( "SELECT COUNT(*) FROM information_schema.tables
WHERE table_name='proxies' "); 
int
<x-tab>
     </x-tab><x-tab>
        </x-tab>GetIntFromSQL(
mystring& sql ) 
{<x-tab>       </x-tab><x-tab>
        </x-tab>
// if there's more than one
record in the ResultSet, still only returns the first float 
<x-tab>
        </x-tab>
int
<x-tab>
     </x-tab><x-tab>
        </x-tab>retVal = -1; 
<x-tab>        </x-tab>
PGresult*<x-tab>       </x-tab>res =
GetQueryResult( sql ); 
<x-tab>        </x-tab>
if
 ( res ) 
<x-tab>        </x-tab>{<x-tab>
       </x-tab>
int
 nTuples = PQntuples(res); 
<x-tab>        </x-tab><x-tab>
        </x-tab>
int
 nFields = PQnfields(res); 
<x-tab>        </x-tab><x-tab>
        </x-tab>
if
 ( nTuples > 0  && 
nFields > 0 ) 
<x-tab>        </x-tab><x-tab>
        </x-tab>{<x-tab>
       </x-tab>
char
*<x-tab>   </x-tab>val =
PQgetvalue(res,0,0);<x-tab>      </x-tab>
<x-tab>        </x-tab>
// get first column, first
field 
<x-tab>
        </x-tab><x-tab>
        </x-tab><x-tab>
        </x-tab>retVal = atoi(
val ); 
<x-tab>        </x-tab><x-tab>
        </x-tab>} 
<x-tab>        </x-tab><x-tab>
        </x-tab>PQclear( res
); 
<x-tab>        </x-tab>} 
<x-tab>        </x-tab>
return
<x-tab>  </x-tab>retVal; 
} 
PGresult*<x-tab>
       </x-tab>GetQueryResult(
mystring& sql ) 
{<x-tab>       </x-tab><x-tab>
        </x-tab>
// run a query that may
return a result set 
<x-tab>
        </x-tab>PGresult*<x-tab>
       </x-tab>res = PQexec( conn,
sql.c_str() ); 
<x-tab>        </x-tab>
if
 ( res ) 
<x-tab>        </x-tab>{<x-tab>
       </x-tab>
int
<x-tab>
     </x-tab>status = PQresultStatus(res); 
<x-tab>        </x-tab><x-tab>
        </x-tab>
if
 ( status != PGRES_TUPLES_OK ) 
<x-tab>        </x-tab><x-tab>
        </x-tab>{<x-tab>
       </x-tab><x-tab>
        </x-tab>
// what happened? 
<x-tab>
        </x-tab><x-tab>
        </x-tab><x-tab>
        </x-tab>fprintf( stderr,

"GetQueryResult(%s) ->
%s\n", sql.c_str(),
PQerrorMessage(conn) ); 
<x-tab>        </x-tab><x-tab>
        </x-tab><x-tab>
        </x-tab>PQclear( res
);<x-tab> </x-tab><x-tab>
        </x-tab><x-tab>
        </x-tab><x-tab>
        </x-tab><x-tab>
        </x-tab>
// possibly moot 
<x-tab>
        </x-tab><x-tab>
        </x-tab><x-tab>
        </x-tab>res = NULL; 
<x-tab>        </x-tab><x-tab>
        </x-tab>} 
<x-tab>        </x-tab>} 
<x-tab>        </x-tab>
else 
<x-tab>
        </x-tab>{<x-tab>
       </x-tab>fprintf( stderr,

"GetQueryResult: insufficient memory to run:
%s\n", sql.c_str() ); 
<x-tab>        </x-tab><x-tab>
        </x-tab>
throw


"GetQueryResult: insufficient
memory"; 
<x-tab>        </x-tab>} 
<x-tab>        </x-tab>
return
<x-tab>  </x-tab>res; 
} 
At 02:14 AM 1/7/2010, you wrote: 
<blockquote type=cite class=cite cite="">-----BEGIN PGP SIGNED
MESSAGE----- 
Hash: SHA1 
On Thu, Jan 07, 2010 at 04:11:03AM +0000, Mike Landis wrote: 
> 
> The following bug has been logged online: 
> 
> Bug reference:      5268 
> Logged by:         
Mike Landis 
> Email address:      mlandis(at)pnmx(dot)com 
> PostgreSQL version: 8.4.1 
> Operating system:   Vista 
> Description:        PQgetvalue
incorrectly returns 0 
> Details: 
> 
> When I execute the following SQL: 
> 
> "SELECT COUNT(*) FROM information_schema.tables WHERE
table_name='proxies'" 
> 
> in the PGAdmmin 1.10.0, rev 7945-7946 query tool, I get
"1" (the correct 
> answer).  When I run the exact same SQL in a C program, I get a
result set 
> with one tuple and one field (so far so good), but when I run 
> PQgetvalue(resultSet,0,0) I get "0" (wrong answer). 
> 
> Am I missing something?  You can't do squat in a client program
without 
> PQgetvalue().  Is any sort of regression test being run against
libpq 
> functions? 
Hm. I don't know for sure, but I'd assume that PGAdmin relies on 
libpq... 
> What can I do to get this resolved? 
Could you show us a more complete test case? That might help in 
pin-pointing the problem. 
Regards 
- -- tomÃ¡s 
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Re: BUG #5268: PQgetvalue incorrectly returns 0 at 2010-01-07 07:14:48 from tomas

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Re: BUG #5268: PQgetvalue incorrectly returns 0 at 2010-01-07 18:01:47 from Robert Haas

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