Retry metadata locks. Add --plugin to make testing this easier. Print --statistics in cleanup tasks. Add a helper script for myself: sandbox/set-mysql.

t/pt-online-schema-change/samples/plugins/block_create_triggers.pm

@@ -0,0 +1,46 @@
+package pt_online_schema_change_plugin;
+
+use strict;
+use warnings FATAL => 'all';
+use English qw(-no_match_vars);
+use constant PTDEBUG => $ENV{PTDEBUG} || 0;
+
+sub new {
+   my ($class, %args) = @_;
+   my $self = { %args };
+   return bless $self, $class;
+}
+
+sub init {
+   my ($self, %args) = @_;
+   print "PLUGIN: init()\n";
+   $self->{orig_tbl} = $args{orig_tbl};
+}
+
+sub before_create_triggers {
+   my ($self, %args) = @_;
+   print "PLUGIN: before_create_triggers()\n";
+
+   my $dbh      = $self->{aux_cxn}->dbh;
+   my $orig_tbl = $self->{orig_tbl};
+
+   # Start a trx and get a metadata lock on the table being altered.
+   $dbh->do('SET autocommit=0');
+   $dbh->{AutoCommit} = 0;
+   $dbh->do("START TRANSACTION");
+   $dbh->do("SELECT * FROM " . $orig_tbl->{name});
+
+   return;
+}
+
+sub after_create_triggers {
+   my ($self, %args) = @_;
+   print "PLUGIN: after_create_triggers()\n";
+
+   my $dbh = $self->{aux_cxn}->dbh;
+
+   # Commit the trx to release the metadata lock.
+   $dbh->commit();
+}
+
+1;

t/pt-online-schema-change/samples/plugins/block_swap_tables.pm

@@ -0,0 +1,46 @@
+package pt_online_schema_change_plugin;
+
+use strict;
+use warnings FATAL => 'all';
+use English qw(-no_match_vars);
+use constant PTDEBUG => $ENV{PTDEBUG} || 0;
+
+sub new {
+   my ($class, %args) = @_;
+   my $self = { %args };
+   return bless $self, $class;
+}
+
+sub init {
+   my ($self, %args) = @_;
+   print "PLUGIN: init()\n";
+   $self->{orig_tbl} = $args{orig_tbl};
+}
+
+sub before_swap_tables {
+   my ($self, %args) = @_;
+   print "PLUGIN: before_swap_tables()\n";
+
+   my $dbh      = $self->{aux_cxn}->dbh;
+   my $orig_tbl = $self->{orig_tbl};
+
+   # Start a trx and get a metadata lock on the table being altered.
+   $dbh->do('SET autocommit=0');
+   $dbh->{AutoCommit} = 0;
+   $dbh->do("START TRANSACTION");
+   $dbh->do("SELECT * FROM " . $orig_tbl->{name});
+
+   return;
+}
+
+sub before_drop_triggers {
+   my ($self, %args) = @_;
+   print "PLUGIN: before_drop_triggers()\n";
+
+   my $dbh = $self->{aux_cxn}->dbh;
+
+   # Commit the trx to release the metadata lock.
+   $dbh->commit();
+}
+
+1;

t/pt-online-schema-change/samples/stats-dry-run.txt

@@ -2,6 +2,9 @@ Starting a dry run.  `bug_1045317`.`bits` will not be altered.  Specify --execut
 Not dropping triggers because this is a dry run.
 Dropping new table...
 Dropped new table OK.
+# Event  Count
+# ====== =====
+# INSERT     0
 Dry run complete.  `bug_1045317`.`bits` was not altered.
 Creating new table...
 Created new table bug_1045317._bits_new OK.
@@ -11,6 +14,3 @@ Not creating triggers because this is a dry run.
 Not copying rows because this is a dry run.
 Not swapping tables because this is a dry run.
 Not dropping old table because this is a dry run.
-# Event  Count
-# ====== =====
-# INSERT     0

t/pt-online-schema-change/samples/stats-execute-5.5.txt

@@ -1,6 +1,10 @@
 Altering `bug_1045317`.`bits`...
 Dropping triggers...
 Dropped triggers OK.
+# Event              Count
+# ================== =====
+# INSERT                 1
+# mysql_warning_1592     1
 Successfully altered `bug_1045317`.`bits`.
 Creating new table...
 Created new table bug_1045317._bits_new OK.
@@ -14,7 +18,3 @@ Swapping tables...
 Swapped original and new tables OK.
 Dropping old table...
 Dropped old table `bug_1045317`.`_bits_old` OK.
-# Event              Count
-# ================== =====
-# INSERT                 1
-# mysql_warning_1592     1