Merge lp:~percona-toolkit-dev/percona-toolkit/pt-osc-5.0-fix into lp:percona-toolkit/2.1

[Daniel Nichter]

[Daniel Nichter (daniel-nichter)]

review: Approve

=== modified file 'bin/pt-online-schema-change'
--- bin/pt-online-schema-change	2012-12-11 14:48:44 +0000
+++ bin/pt-online-schema-change	2012-12-11 22:54:22 +0000
@@ -7860,10 +7860,15 @@
    # Although triggers were introduced in 5.0.2, "Prior to MySQL 5.0.10,
    # triggers cannot contain direct references to tables by name."
    # ########################################################################   
-   if ( VersionParser->new($cxn->dbh()) < '5.0.10' ) {
+   my $server_version = VersionParser->new($cxn->dbh());
+   if ( $server_version < '5.0.10' ) {
       die "This tool requires MySQL 5.0.10 or newer.\n";
    }
 
+   # Use LOCK IN SHARE mode unless MySQL 5.0 because there's a bug like
+   # http://bugs.mysql.com/bug.php?id=45694
+   my $lock_in_share_mode = $server_version < '5.1' ? 0 : 1;
+
    # ########################################################################
    # Setup lag and load monitors.
    # ########################################################################   
@@ -8698,7 +8703,7 @@
       dml                => $dml,
       select             => $select,
       callbacks          => $callbacks,
-      lock_in_share_mode => 1,
+      lock_in_share_mode => $lock_in_share_mode,
       OptionParser       => $o,
       Quoter             => $q,
       TableParser        => $tp,
@@ -10082,6 +10087,29 @@
 
 You must specify C<--alter "DROP FOREIGN KEY _fk_foo">.
 
+=item *
+
+The tool does not use C<LOCK IN SHARE MODE> with MySQL 5.0 because it can
+cause a slave error which breaks replication:
+
+   Query caused different errors on master and slave. Error on master:
+   'Deadlock found when trying to get lock; try restarting transaction' (1213),
+   Error on slave: 'no error' (0). Default database: 'pt_osc'.
+   Query: 'INSERT INTO pt_osc.t (id, c) VALUES ('730', 'new row')'
+
+The error happens when converting a MyISAM table to InnoDB because MyISAM
+is non-transactional but InnoDB is transactional.  MySQL 5.1 and newer
+handle this case correctly, but testing reproduces the error 5% of the time
+with MySQL 5.0.
+
+This is a MySQL bug, similar to L<http://bugs.mysql.com/bug.php?id=45694>,
+but there is no fix or workaround in MySQL 5.0.  Without C<LOCK IN SHARE MODE>,
+tests pass 100% of the time, so the risk of data loss or breaking replication
+should be negligible.
+
+B<Be sure to verify the new table if using MySQL 5.0 and converting
+from MyISAM to InnoDB!>
+
 =back
 
 =item --alter-foreign-keys-method

=== modified file 't/pt-online-schema-change/bugs.t'
--- t/pt-online-schema-change/bugs.t	2012-11-08 23:38:07 +0000
+++ t/pt-online-schema-change/bugs.t	2012-12-11 22:54:22 +0000
@@ -236,6 +236,35 @@
 }
 
 # #############################################################################
+# Something like http://bugs.mysql.com/bug.php?id=45694 means we should not
+# use LOCK IN SHARE MODE with MySQL 5.0.
+# #############################################################################
+$sb->load_file('master', "$sample/basic_no_fks_innodb.sql");
+
+($output, $exit_status) = full_output(
+    sub { pt_online_schema_change::main(@args,
+            "$master_dsn,D=pt_osc,t=t",
+            "--alter", "add column (foo int)",
+            qw(--execute --print))
+   },
+);
+
+if ( $sandbox_version eq '5.0' ) {
+   unlike(
+      $output,
+      qr/LOCK IN SHARE MODE/,
+      "No LOCK IN SHARE MODE for MySQL $sandbox_version"
+   );
+}
+else {
+   like(
+      $output,
+      qr/LOCK IN SHARE MODE/,
+      "LOCK IN SHARE MODE for MySQL $sandbox_version",
+   );
+}
+
+# #############################################################################
 # Done.
 # #############################################################################
 $sb->wipe_clean($master_dbh);