diff --git a/t/pt-online-schema-change/samples/basic_no_fks.sql b/t/pt-online-schema-change/samples/basic_no_fks.sql
index ee9b672e..0c4cbacc 100644
--- a/t/pt-online-schema-change/samples/basic_no_fks.sql
+++ b/t/pt-online-schema-change/samples/basic_no_fks.sql
@@ -6,7 +6,7 @@ CREATE TABLE t (
   c  char(32),
   d  date,
   unique index (c(32))
-) ENGINE=MyISAM;
+) ENGINE=InnoDB;
 INSERT INTO pt_osc.t VALUES
    (null, 'a', now()),
    (null, 'b', now()),
diff --git a/t/pt-online-schema-change/samples/query_table.pl b/t/pt-online-schema-change/samples/query_table.pl
index 0a9e3f96..55258b4a 100755
--- a/t/pt-online-schema-change/samples/query_table.pl
+++ b/t/pt-online-schema-change/samples/query_table.pl
@@ -4,9 +4,12 @@ use strict;
 use warnings FATAL => 'all';
 use English qw(-no_match_vars);
 use DBI;
-use Time::HiRes qw(usleep time);
+use Time::HiRes qw(sleep time);
+use Test::More qw();
 
-my ($host, $port, $db, $tbl, $pkcol, $stop_file, $pid_file, $sleep_time) = @ARGV;
+use constant PTDEBUG => $ENV{PTDEBUG} || 0;
+
+my ($host, $port, $db, $tbl, $pkcol, $stop_file, $pid_file, $sleep) = @ARGV;
 
 die "I need a pid_file argument" unless $pid_file;
 open my $fh, '>', $pid_file or die $OS_ERROR;
@@ -19,63 +22,87 @@ my $dbh = DBI->connect(
    {RaiseError => 1, AutoCommit => 0, ShowErrorStatement => 1, PrintError => 0},
 );
 
-my $sleep = ($sleep_time || 0.001) * 1_000_000;
+$sleep ||= 0.001;
+
 my $cnt   = 0;
-my @del;
-my @upd;
-my @ins;
+my (@del, %del);
+my (@upd, %upd);
+my (@ins, %ins);
+
+use constant TYPE_DELETE => 1;
+use constant TYPE_UPDATE => 2;
 
 my $start_xa = "START TRANSACTION /*!40108 WITH CONSISTENT SNAPSHOT */";
 $dbh->do($start_xa);
 
+sub commit {
+   eval {
+      $dbh->commit;
+   };
+   if ( $EVAL_ERROR ) {
+      Test::More::diag($EVAL_ERROR);
+      $dbh->do("ROLLBACK");
+   }
+   else {
+      map { $del{$_}++ } @del;
+      map { $ins{$_}++ } @ins;
+      map { $upd{$_}++ } @upd;
+   }
+   @del = ();
+   @ins = ();
+   @upd = ();
+   $cnt = 0;
+}
+
 for my $i ( 1..5_000 ) {
    last if -f $stop_file;
-
+   my $id   = 0;
+   my $type = '';
    eval {
       # We do roughly 25% DELETE, 25% UPDATE and 50% INSERT.
-      my $x = int(rand(5));
-      if ($x == 1) {
-         my $id = int(rand(500)) || 1;
+      my $type = int(rand(5));
+      if ($type == TYPE_DELETE) {
+         $id = int(rand(500)) || 1;
          $dbh->do("delete from $db.$tbl where $pkcol=$id");
          # To challenge the tool, we *do* (or can) delete the same id twice.
          # But to keep the numbers straight, we only record each deleted
          # id once.
-         push @del, $id unless grep { $_ == $id } @del;
+         push @del, $id;
       }
-      elsif ($x == 2) {
-         my $id = int(rand(500)) || 1;
-         if ( !grep { $_ == $id } @del ) {
+      elsif ($type == TYPE_UPDATE) {
+         $id = int(rand(500)) || 1;
+         # Update a row if we haven't already deleted it.
+         if ( !$del{$id} ) {
             my $t=time;
             $dbh->do("update $db.$tbl set c='updated row $t' where $pkcol=$id");
             push @upd, $id;
          }
       }
       else {
-         my $id = 500 + $i;
-         my $t=time;
+         $id = 500 + $i;
+         my $t  = time;
          $dbh->do("insert ignore into $db.$tbl ($pkcol, c) values ($id, 'new row $t')");
          push @ins, $id;
       }
-
-      # COMMIT every N statements
-      if ( $cnt++ > 5 ) {
-         $dbh->do('COMMIT');
-         $cnt = 0;
-         usleep($sleep);
-         $dbh->do($start_xa);
-      }
    };
    if ( $EVAL_ERROR ) {
-      warn $EVAL_ERROR;
-      last;
+      Test::More::diag($EVAL_ERROR);
+      sleep $sleep;
+   }
+
+   # COMMIT every N statements.  With PXC this can fail.
+   if ( $cnt++ > 5 ) {
+      commit();
+      sleep($sleep);
+      $dbh->do($start_xa);
    }
 }
 
-$dbh->do('COMMIT');
+commit();
 $dbh->disconnect();
 
-print "deleted:"  . join(',', @del) . "\n";
-print "updated:"  . join(',', @upd) . "\n";
-print "inserted:" . join(',', @ins) . "\n";
+print "deleted:"  . join(',', sort keys %del) . "\n";
+print "updated:"  . join(',', sort keys %upd) . "\n";
+print "inserted:" . join(',', sort keys %ins) . "\n";
 
 exit 0;