FreeTDS Development Group

[Brian Bruns <camber AT ais.org>]

Ok this appears to affect only ctlib (which DBD::Sybase uses), which is
why we didn't catch it last time leaks were checked (which I believe was
preformed under dblib).

The following replacement for ct_cmd_drop in src/ctlib/ct.c should fix it.
It's a hold over from the days when query length was fixed.  
(Warning: untested code)

CS_RETCODE ct_cmd_drop(CS_COMMAND *cmd)
{
     tdsdump_log(TDS_DBG_FUNC, "%L inside ct_cmd_drop()\n");
     if (cmd) {
        if (cmd->query) free(cmd->query);
        free(cmd);
     }
     return CS_SUCCEED;
}

I'll try to test it and get it checked in this evening.

Brian

On Thu, 13 Sep 2001, Eric Deutsch wrote:

> 
> Hi again, I've done a little more investigating, and I've come back to plead
> for help.  Situation is the same as below:
> 
> If I do in perl with DBD::Sybase 0.91:
> 
> $querystring="INSERT INTO leaktest (intfield,charfield,realfield) VALUES (
> 20,'chicken',3.1415 )";
> while ( 1 == 1 ) {
>   $dbh->do($SQLstring);
>   print ".";
> }
> 
> and watch my process with `top` it grows forever at a rate of 6 MB per
> minute.  However, if I do the following in a test C program:
> 
>    static char sql_query[]   = "INSERT INTO dbaccesstests
> (intfield,charfield,realfield) VALUES ( 20,'butter',3.1415 )";
>    while ( 1 == 1 ) {
>       rc = run_query(tds,sql_query);
>       if (rc != TDS_SUCCEED) {
>          fprintf(stderr, "run_query() failed\n");
>          return 1;
>       }
>       fprintf(stdout, ".");
>       fflush(stdout);
>    }
> 
> I can run this program for many minutes without a single kB being added to
> the resident memory of the process.  I'm using the run_query() function from
> t0004.c.
> 
> So it appears that the FreeTDS C API functions aren't leaking as such, but
> somehow the interaction between Perl DBI/DBD and FreeTDS is.
> 
> As a further test, I did a loop where the SQL command was:
> 
> $querystring="INSERT INTO dbaccesstests (intfield,charfield,realfield)
> VALUES (
> 20,'butter',3.1415 ) /*
> ****************************************************************************
> ****************************************************************************
> ****************************************************************************
> ****************************************************************************
> ******************************************************************** */";
> 
> and as I guessed, the leak rate tripled!  Thus is looks very much like
> somewhere a copy of the query string is being made and not freed.
> 
> I really don't know how to go about figuring this out.  Anyone out there
> able to help or repro?  I can send actual C and Perl programs used.
> 
> many thanks,
> Eric
> 
> 
> 
> 
> > -----Original Message-----
> > From: bounce-freetds-127899 AT franklin.oit.unc.edu
> > [mailto:bounce-freetds-127899 AT franklin.oit.unc.edu]On Behalf Of Eric
> > Deutsch
> > Sent: Monday, September 10, 2001 6:33 PM
> > To: TDS Development Group
> > Subject: [freetds] Memory leak when doing many INSERTs
> >
> > Hi all, I've noticed what appears to be some memory leaking while
> > doing lots
> > of INSERTS.  I'm using Perl 5.6.0 + DBD::Sybase 0.91 + FreeTDS (both 0.51a
> > and latest CVS) under Red Hat 7.0 connecting to SQL Server 2000.
> >
> > If I do:
> >
> > $querystring="INSERT INTO leaktest (intfield,charfield,realfield) VALUES (
> > 20,'chicken',3.1415 )";
> > while ( 1 == 1 ) {
> >   $dbh->do($SQLstring);
> >   print ".";
> > }
> >
> > after a suitable setup, and watch my process with top, the memory
> > used grows
> > and grows at a rate of maybe 5 MB/min.  There's no difference if I use
> > prepare() and execute().
> >
> > I have some real code (as opposed to the above example) that is
> > parsing and
> > loading some huge datasets from files into a my DB and after one
> > particularly large set, my process was killed because it hogged all the
> > client machine's memory (probably after running for an hour).
> > This is a bit
> > of a snag in what I'm trying to do.  I could start breaking up
> > the work, but
> > this is awkward for various reasons.
> >
> > Has anyone encountered/studied/noticed this before?  Any advice?
> > I suppose
> > I could try taking Perl out of the loop to see if it's a FreeTDS
> > issue or a
> > Perl DBI + DBD::Sybase issue.
> >
> > I'm assuming it is not unreasonable to expect a Perl script to be able to
> > run INSERTs until SQL Server explodes without running into memory
> > issues, is
> > that true?
> >
> > thanks,
> > Eric
> >
> >
> >
> >
> >
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