I have a situation with DBI and the Sybase drivers. If I specify a TDS level, and I use a query with placeholders, and that query returns no results, the fetchall_arrayref() call hangs. If I don't do all three of those things, the call returns an array, as expected.

Steps to reproduce on Ubuntu 20.04:

Install perlbrew 

sudo apt install gcc make -y
wget -O - https://install.perlbrew.pl | bash
echo "source ~/perl5/perlbrew/etc/bashrc" >> ~/.profile
source ~/perl5/perlbrew/etc/bashrc
perlbrew install perl-5.33.8
perlbrew switch perl-5.33.8
perlbrew install-cpanm

[download]
Install FreeTDS 
wget ftp://ftp.freetds.org/pub/freetds/stable/freetds-1.2.20.tar.gz
tar xfvz freetds-1.2.20.tar.gz
cd freetds-1.2.20/
./configure --prefix=/home/username/tdslib
make
make install

[download]
Install DBI and Sybase 
export SYBASE=/home/username/tdslib
cpanm install DBI
cpanm DBD::Sybase --verbose --force

[download]
run test script 
use warnings;
use strict;
use DBI;
use Data::Dumper;

runTest('');
runTest(';tdsLevel=CS_TDS_495');

sub runTest {
    my ($tdsLevel) = @_;
    my $dsn        = "dbi:Sybase:server=172.28.79.294$tdsLevel";
    my $UserName   = 'myusername';
    my $Password   = 'supersecretpassword';
    my $dbh        = DBI->connect( $dsn, $UserName, $Password, )
      or ( print "Can't connect to the DB: $DBI::errstr\n" and die );

    print "\nTesting no placeholders, no results $dsn\n";
    my $sth = $dbh->prepare("select 'test' where 1=0");
    $sth->execute();
    my $results = $sth->fetchall_arrayref( {} );
    print Dumper $results;

    print "\nTesting placeholders with results $dsn\n";
    my $sthSecond = $dbh->prepare("select ? where 1=1");
    $sthSecond->execute("test");
    my $resultsSecond = $sthSecond->fetchall_arrayref( {} );
    print Dumper $resultsSecond;

    print "\nTesting placeholders with no results $dsn\n";
    my $sthThird = $dbh->prepare("select ? where 1=0");
    $sthThird->execute("test");
    my $resultsThird = $sthThird->fetchall_arrayref( {} );
    print Dumper $resultsThird;

    $dbh->disconnect();
}

[download]
The test code above runs a total of six queries with different combinations of (1) specifying the TDS level (2), running a query with or without placeholders , and (3) running a query that does or does not return results. The test query that produces the hang is run last.

Full disclosure: I first wrote this test script on one computer and then created a virtual machine to test the "steps to reproduce" shown above. On the second computer, the connection with no TDS level specified does not work. However, I believe this to be a separate issue.

The SQL Server here is MS SQL Server Standard version 12.0.5223.6

In reply to fetchall_arrayref hangs with placeholders query with no results by TieUpYourCamel

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