From c0ea3179c3ed23b6aad357e4cf24e73fbdd5494c Mon Sep 17 00:00:00 2001
From: frank-cizmich <frank.cizmich@percona.com>
Date: Wed, 23 Sep 2015 19:21:42 -0300
Subject: [PATCH] pt-osc fixed fk underscore toggling lp1498128

---
 bin/pt-online-schema-change                   |  7 +--
 .../rename_fk_constraints.t                   | 46 +++++++++----------
 .../samples/bug-1215587.sql                   |  9 +++-
 3 files changed, 31 insertions(+), 31 deletions(-)

diff --git a/bin/pt-online-schema-change b/bin/pt-online-schema-change
index ef209d9f..de40257e 100755
--- a/bin/pt-online-schema-change
+++ b/bin/pt-online-schema-change
@@ -9880,11 +9880,8 @@ sub create_new_table {
       # This is in contrast to previous behavior were we added underscores
       # indefinitely, sometimes exceeding the allowed name limit
       # https://bugs.launchpad.net/percona-toolkit/+bug/1215587 
-      if ( $sql =~ /CONSTRAINT `_/ ) {
-         $sql =~ s/^  CONSTRAINT `_/  CONSTRAINT `/gm;
-      } else {
-         $sql =~ s/^  CONSTRAINT `/  CONSTRAINT `_/gm;
-      }
+      $sql =~ s/^  CONSTRAINT `(_?)/'  CONSTRAINT `'.($1 eq '' ? '_' : '')/gme;
+
       if ( $o->get('default-engine') ) {
          $sql =~ s/\s+ENGINE=\S+//;
       }
diff --git a/t/pt-online-schema-change/rename_fk_constraints.t b/t/pt-online-schema-change/rename_fk_constraints.t
index cb1aabfe..1c8b13f5 100644
--- a/t/pt-online-schema-change/rename_fk_constraints.t
+++ b/t/pt-online-schema-change/rename_fk_constraints.t
@@ -42,8 +42,7 @@ my $sample  = "t/pt-online-schema-change/samples/";
 $sb->load_file('master', "$sample/bug-1215587.sql");
 
 # run once: we expect constraint names to be prefixed with one underscore
-# note: We're running just a neutral no-op alter. We are only interested in constraint name
-# changes.
+# if they havre't one, and to remove one if they already do.
 ($output, $exit_status) = full_output(
    sub { pt_online_schema_change::main(@args,
       "$master_dsn,D=bug1215587,t=Table1",
@@ -52,24 +51,24 @@ $sb->load_file('master', "$sample/bug-1215587.sql");
 );
 
 
-my $constraints = $master_dbh->selectall_hashref("SELECT CONSTRAINT_NAME, TABLE_NAME FROM information_schema.KEY_COLUMN_USAGE WHERE table_schema='bug1215587' and (TABLE_NAME='Table1' OR TABLE_NAME='Table2') and CONSTRAINT_NAME LIKE '%fkey%'", 'table_name'); 
+my $constraints = $master_dbh->selectall_arrayref("SELECT TABLE_NAME, CONSTRAINT_NAME FROM information_schema.KEY_COLUMN_USAGE WHERE table_schema='bug1215587' and (TABLE_NAME='Table1' OR TABLE_NAME='Table2') and CONSTRAINT_NAME LIKE '%fkey%' ORDER BY TABLE_NAME, CONSTRAINT_NAME"); 
 
 
-is(
-   $constraints->{Table1}->{constraint_name},
-   '_fkey1',
-   "Altered table: constraint name prefixed one underscore after 1st run"
+is_deeply(
+   $constraints,
+   [
+      ['Table1', 'fkey1a'],
+      ['Table1', '_fkey1b'],
+      ['Table2', 'fkey2b'],
+      ['Table2', '_fkey2a'],
+   ],
+   "First run adds or removes underscore from constraint names, accordingly"
 );
 
-is(
-   $constraints->{Table2}->{constraint_name}, 
-   '_fkey2',
-   "Child table  : constraint name prefixed one underscore after 1st run"
-);
 
 
 # run second time 
-# we expect underscores to be removed
+# we expect constraints to be the same as we started (toggled back)
 ($output, $exit_status) = full_output(
    sub { pt_online_schema_change::main(@args,
       "$master_dsn,D=bug1215587,t=Table1",
@@ -77,19 +76,18 @@ is(
       qw(--execute)) },
 );
 
-$constraints = $master_dbh->selectall_hashref("SELECT CONSTRAINT_NAME, TABLE_NAME FROM information_schema.KEY_COLUMN_USAGE WHERE table_schema='bug1215587' and (TABLE_NAME='Table1' OR TABLE_NAME='Table2') and CONSTRAINT_NAME LIKE '%fkey%'", 'table_name'); 
+$constraints = $master_dbh->selectall_arrayref("SELECT TABLE_NAME, CONSTRAINT_NAME FROM information_schema.KEY_COLUMN_USAGE WHERE table_schema='bug1215587' and (TABLE_NAME='Table1' OR TABLE_NAME='Table2') and CONSTRAINT_NAME LIKE '%fkey%' ORDER BY TABLE_NAME, CONSTRAINT_NAME"); 
 
 
-is(
-   $constraints->{'Table1'}->{constraint_name},  
-   'fkey1',
-   "Altered table: constraint name removed underscore after 2nd run"
-);
-
-is(
-   $constraints->{'Table2'}->{constraint_name}, 
-   'fkey2',
-   "Child table  : constraint name removed underscore after 2nd run"
+is_deeply(
+   $constraints,
+   [
+      ['Table1', 'fkey1b'],
+      ['Table1', '_fkey1a'],
+      ['Table2', 'fkey2a'],
+      ['Table2', '_fkey2b'],
+   ],
+   "Second run toggles constraint names back to how they were"
 );
 
 
diff --git a/t/pt-online-schema-change/samples/bug-1215587.sql b/t/pt-online-schema-change/samples/bug-1215587.sql
index 1e6a5152..3d4b067f 100644
--- a/t/pt-online-schema-change/samples/bug-1215587.sql
+++ b/t/pt-online-schema-change/samples/bug-1215587.sql
@@ -16,8 +16,13 @@ CREATE TABLE `Table2` (
 ) ENGINE=InnoDB DEFAULT CHARSET=latin1;
 
 ALTER TABLE `Table1`
-  ADD CONSTRAINT `fkey1` FOREIGN KEY (`T2ID`) REFERENCES `Table2` (`ID`) ON DELETE NO ACTION;
+  ADD CONSTRAINT `_fkey1a` FOREIGN KEY (`T2ID`) REFERENCES `Table2` (`ID`) ON DELETE NO ACTION;
+
+ALTER TABLE `Table1`
+  ADD CONSTRAINT `fkey1b` FOREIGN KEY (`T2ID`) REFERENCES `Table2` (`ID`) ON DELETE NO ACTION;
 
 ALTER TABLE `Table2`
-  ADD CONSTRAINT `fkey2` FOREIGN KEY (`ID`) REFERENCES `Table1` (`T2ID`) ON DELETE NO ACTION;
+  ADD CONSTRAINT `fkey2a` FOREIGN KEY (`ID`) REFERENCES `Table1` (`T2ID`) ON DELETE NO ACTION;
 
+ALTER TABLE `Table2`
+  ADD CONSTRAINT `_fkey2b` FOREIGN KEY (`ID`) REFERENCES `Table1` (`T2ID`) ON DELETE NO ACTION;