FreeTDS Development Group

[Michael Peppler <mpeppler AT peppler.org>]

Brian Bruns writes:
 > 
 > Ok, I follow the flow of what is happening.  I'm just not sure what should
 > be happening under ctlib.  The doc is a little weak on the subject.
 > 
 > When freetds runs a query with no rows returned, ct_results() returns
 > CS_END_DATA and sets res_type to CS_CMD_DONE. DBD::Sybase takes this and
 > sets the query to a nonactive state (DBI_ACTIVE_off()). 
 > 
 > Curiously enough, SQSH doesn't seem to mind. I'll check tommorow what the
 > behaviour should be.  Once that is known it should be trivial to fix.

Here's a trace of this query using the Sybase libraries:

    -> execute for DBD::Sybase::st (DBI::st=HASH(0x815e540)~0x8114910)
    syb_st_execute() -> ct_command() OK
    syb_st_execute() -> ct_send() OK
    st_next_result() -> ct_results(4040) == 1
    ct_res_info() returns 5 columns
describe() retcode = 1
    <- execute= -1 at none.pl line 24.
Retrieving data 0
    -> fetchrow for DBD::Sybase::st (DBI::st=HASH(0x815e540)~0x8114910)
    st_next_result() -> ct_results(4046) == 1
ct_execute() final retcode = -205
    syb_st_fetch() -> st_next_results() == 4046
    syb_st_fetch() -> resetting ACTIVE, moreResults, dyn_execed
    <- fetchrow= ( ) [0 items] at none.pl line 30.
    -> finish for DBD::Sybase::st (DBI::st=HASH(0x815e540)~0x8114910)
    <- finish= 1 at none.pl line 40.
    -> disconnect for DBD::Sybase::db (DBI::db=HASH(0x80cee5c)~0x80cee50)
    syb_db_disconnect() -> ct_close()


The first result type returned by ct_results is CS_ROW_RESULT. At that 
point we get the row description, and then we fetch the first row. As
ct_fetch() returns CS_END_DATA, we call ct_results() again, which now
returns CS_CMD_DONE, and now we reset the active status of the
statement handle.

So it looks like you return CS_CMD_DONE one step too early in this
case.

Michael

 > 
 > Brian
 > 
 > On Tue, 28 Sep 1999, Jaye Mathisen wrote:
 > 
 > > 
 > > I'm running on FreeBSD, using FreeTDS 0.46, and DBD::Sybase-0.19,
 > > DBI-1.12.  The server is currently running SQL 6.5, SP 5A.
 > > 
 > > The dopey question I asked about the rowcount thing turned out to
 > > have a bit more significance than I first thought, because my problem 
 > > was that I couldn't detect queries that returned 0 rows.
 > > 
 > > The following output occurs from the enclosed (short) script.  I don't
 > > believe the while() loop should succeed, because the query returns 0 
 > > rows.
 > > But I get this error message, rather than just skipping the loop.
 > > 
 > > Here's the output:
 > > 
 > > backmaster# ./ex.pl
 > > Unknown property 7
 > > Retrieving data 0
 > > no statement executing at ./ex.pl line 44.
 > > 
 > > The query is "select * from customer where 1=0".  sysusers can
 > > be substituted easily for customer, the point is just to return
 > > 0 rows.  And you'll have to change the "use plat" to "use
 > > whateverdatabase".
 > > 
 > > Any ideas on what to look for?  
 > > 
 > > --- short script ---
 > > #!/usr/local/bin/perl
 > > 
 > > my $q = "select * from customer where 1=0";
 > > 
 > > use DBI;
 > > 
 > > if(-f "./PWD")
 > >  {
 > >         open(PWD, "./PWD") || die "$_/PWD is not readable: $!\n";
 > >         while(<PWD>)
 > >         {
 > >             chop;
 > >             s/^\s*//;
 > >             next if(/^\#/ || /^\s*$/);
 > >             ($l, $r) = split(/=/);
 > >             $Uid = $r if($l eq UID);
 > >             $Pwd = $r if($l eq PWD);
 > >             $Srv = $r if($l eq SRV);
 > >         }
 > >         close(PWD);
 > >  }
 > > 
 > > my $dbh = DBI->connect("dbi:Sybase:server=$Srv", $Uid, $Pwd, {PrintError
 > > => 0});
 > > 
 > > die "Unable to connect to $Srv: $DBI::errstr"
 > >     unless $dbh;
 > > 
 > > my $rc;
 > > $rc = $dbh->do("use plat");
 > > 
 > > my $sth;
 > > 
 > > $sth = $dbh->prepare("$q") || warn "Problem\n";
 > > 
 > > if ($sth->execute) {
 > >     
 > >     my $rows = 0;
 > >     my @dat;
 > > 
 > >     print "Retrieving data 0\n";
 > >     while (@dat = $sth->fetchrow) {
 > >         print "Retrieving data\n";
 > >         ++$rows;
 > > 
 > >         foreach (@dat) {
 > >             $_ = '' unless defined($_);
 > >         }
 > >         print "@dat\n";
 > >     }
 > > 
 > >     $sth->finish;
 > > }
 > > 
 > > $dbh->disconnect;
 > > 
 > > 
 > > ---
 > > You are currently subscribed to freetds as: camber AT ais.org
 > > To unsubscribe, forward this message to $subst('Email.Unsub')
 > > 
 > > 
 > 
 > 
 > ---
 > You are currently subscribed to freetds as: mpeppler AT peppler.org
 > To unsubscribe, forward this message to $subst('Email.Unsub')
 > 

-- 
Michael Peppler         -||-  Data Migrations Inc.
mpeppler AT peppler.org    -||-  http://www.mbay.net/~mpeppler
Int. Sybase User Group  -||-  http://www.isug.com
Sybase on Linux mailing list: ase-linux-list AT isug.com