Added a pt-osc plugin to rename a FK to its original name

percona-toolkit/plugins/ptosc_plugin_rename_fk.pl

@@ -0,0 +1,137 @@
+package pt_online_schema_change_plugin;
+
+use strict;
+# use Data::Dumper;
+
+my $table_name;
+my $executed = 0;
+my $OLD_table_fks = {};
+
+
+sub get_fks {
+   my ( $self, $ddl, $opts ) = @_;
+   my $q   = $self->{Quoter};
+   my $fks = {};
+
+   foreach my $fk (
+      $ddl =~ m/CONSTRAINT .* FOREIGN KEY .* REFERENCES [^\)]*\)/mg )
+   {
+      my ( $name ) = $fk =~ m/CONSTRAINT `(.*?)`/;
+      my ( $cols ) = $fk =~ m/FOREIGN KEY \(([^\)]+)\)/;
+      my ( $parent, $parent_cols ) = $fk =~ m/REFERENCES (\S+) \(([^\)]+)\)/;
+
+      my ($db, $tbl) = $q->split_unquote($parent, $opts->{database});
+      my %parent_tbl = (tbl => $tbl);
+      $parent_tbl{db} = $db if $db;
+
+      if ( $parent !~ m/\./ && $opts->{database} ) {
+         $parent = $q->quote($opts->{database}) . ".$parent";
+      }
+
+      $fks->{$name} = {
+         name           => $name,
+         colnames       => $cols,
+         cols           => [ map { s/[ `]+//g; $_; } split(',', $cols) ],
+         parent_tbl     => \%parent_tbl,
+         parent_tblname => $parent,
+         parent_cols    => [ map { s/[ `]+//g; $_; } split(',', $parent_cols) ],
+         parent_colnames=> $parent_cols,
+         ddl            => $fk,
+      };
+}
+
+return $fks;
+}
+
+sub new {
+   my ($class, %args) = @_;
+   my $self = { %args };
+   return bless $self, $class;
+}
+
+sub init {
+   my ($self, %args) = @_;
+   my $table = $args{orig_tbl};
+   $table_name = $table->{name};
+}
+
+sub before_create_new_table {
+   my ($self, %args) = @_;
+   my $dbh     = $self->{cxn}->dbh;
+   my $row = $dbh->selectrow_arrayref("SHOW CREATE TABLE $table_name");
+   my $fks = get_fks($self, $row->[1]);
+
+   while (my ($key, $val) = each (%$fks)) {
+      # print Dumper(\$val);
+      $OLD_table_fks->{"$key"} = {
+         name => $val->{'name'},
+         colnames => $val->{'colnames'}
+      };
+   }
+}
+
+sub after_drop_old_table {
+   my ($self, %args) = @_;
+   my $dbh     = $self->{cxn}->dbh;
+   my $row = $dbh->selectrow_arrayref("SHOW CREATE TABLE $table_name");
+   my $fks = get_fks($self, $row->[1]);
+
+   # print Dumper(\$fks);
+   # Check if any FK in the new table
+   if ((keys %$fks) > 0) {
+      # This is used for DEBUG purposes, can be removed
+      print ">>>>>> PLUGIN to rename the FK's to the original name executed after drop the old table [after_drop_old_table]\n";
+      $executed = 1;
+      change_fk($dbh, $fks);
+   }
+}
+
+sub before_drop_triggers {
+   if ($executed == 0) {
+      my ($self, %args) = @_;
+      my $dbh     = $self->{cxn}->dbh;
+      my $row = $dbh->selectrow_arrayref("SHOW CREATE TABLE $table_name");
+      my $fks = get_fks($self, $row->[1]);
+
+      # Check if any FK in the new table
+      if ((keys %$fks) > 0) {
+         # This is used for DEBUG purposes, can be removed
+         print ">>>>>> PLUGIN to rename the FK's to the original name executed after drop the old table [before_drop_triggers]\n";
+         $executed = 1;
+         change_fk($dbh, $fks);
+      }
+   }
+}
+
+sub change_fk {
+   my ($dbh, $fks) = @_;
+      # Here we start creating the SQL to rename the FK's
+      my $sql_fk = "ALTER TABLE $table_name \n";
+
+      # Variable to control if we need add an extra ","
+      my $count = 0;
+
+      # Loop the FK's to create the SQL
+      while (my ($key_name, $val) = each (%$fks)) {
+         if (exists $OLD_table_fks->{substr($key_name, 1)}) {  
+            if ($count++ > 0) {
+               $sql_fk .= ", \n";
+            }
+
+            $sql_fk = $sql_fk . "  DROP FOREIGN KEY `$key_name`, \n";
+            $sql_fk = $sql_fk . "  ADD CONSTRAINT " . substr($key_name, 1) . 
+               " FOREIGN KEY ( " . $val->{colnames} . ") " .
+               " REFERENCES " . $val->{parent_tblname} . " (" . $val->{parent_colnames} . ") ";
+            # print Dumper(\$OLD_table_fks)
+         }
+      }
+
+      # This will print the SQL to the console used for DEBUG purposes
+      print ">>>>>> PLUGIN SQL: \n$sql_fk\n";
+
+      # This line will effectively execute the SQL to rename (DROP and ADD) the FK's
+      $dbh->do($sql_fk);
+
+}
+
+1;