percona-toolkit/lib/TableSyncGroupBy.pm

# This program is copyright 2007-2011 Baron Schwartz, 2011 Percona Ireland Ltd.
# Feedback and improvements are welcome.
#
# THIS PROGRAM IS PROVIDED "AS IS" AND WITHOUT ANY EXPRESS OR IMPLIED
# WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
# MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
#
# This program is free software; you can redistribute it and/or modify it under
# the terms of the GNU General Public License as published by the Free Software
# Foundation, version 2; OR the Perl Artistic License.  On UNIX and similar
# systems, you can issue `man perlgpl' or `man perlartistic' to read these
# licenses.
#
# You should have received a copy of the GNU General Public License along with
# this program; if not, write to the Free Software Foundation, Inc., 59 Temple
# Place, Suite 330, Boston, MA  02111-1307  USA.
# ###########################################################################
# TableSyncGroupBy package
# ###########################################################################
{
# Package: TableSyncGroupBy
# TableSyncGroupBy is a table sync algo that uses GROUP BY.
# This package syncs tables without primary keys by doing an all-columns GROUP
# BY with a count, and then streaming through the results to see how many of
# each group exist.
package TableSyncGroupBy;

use strict;
use warnings FATAL => 'all';
use English qw(-no_match_vars);
use constant PTDEBUG => $ENV{PTDEBUG} || 0;

sub new {
   my ( $class, %args ) = @_;
   foreach my $arg ( qw(Quoter) ) {
      die "I need a $arg argument" unless $args{$arg};
   }
   my $self = { %args };
   return bless $self, $class;
}

sub name {
   return 'GroupBy';
}

sub can_sync {
   return 1;  # We can sync anything.
}

sub prepare_to_sync {
   my ( $self, %args ) = @_;
   my @required_args = qw(tbl_struct cols ChangeHandler);
   foreach my $arg ( @required_args ) {
      die "I need a $arg argument" unless defined $args{$arg};
   }

   $self->{cols}            = $args{cols};
   $self->{buffer_in_mysql} = $args{buffer_in_mysql};
   $self->{ChangeHandler}   = $args{ChangeHandler};

   $self->{count_col} = '__maatkit_count';
   while ( $args{tbl_struct}->{is_col}->{$self->{count_col}} ) {
      # Prepend more _ until not a column.
      $self->{count_col} = "_$self->{count_col}";
   }
   PTDEBUG && _d('COUNT column will be named', $self->{count_col});

   $self->{done} = 0;

   return;
}

sub uses_checksum {
   return 0;  # We don't need checksum queries.
}

sub set_checksum_queries {
   return;  # This shouldn't be called, but just in case.
}

sub prepare_sync_cycle {
   my ( $self, $host ) = @_;
   return;
}

sub get_sql {
   my ( $self, %args ) = @_;
   my $cols = join(', ', map { $self->{Quoter}->quote($_) } @{$self->{cols}});
   return "SELECT"
      . ($self->{buffer_in_mysql} ? ' SQL_BUFFER_RESULT' : '')
      . " $cols, COUNT(*) AS $self->{count_col}"
      . ' FROM ' . $self->{Quoter}->quote(@args{qw(database table)})
      . ' WHERE ' . ( $args{where} || '1=1' )
      . " GROUP BY $cols ORDER BY $cols";
}

# The same row means that the key columns are equal, so there are rows with the
# same columns in both tables; but there are different numbers of rows.  So we
# must either delete or insert the required number of rows to the table.
sub same_row {
   my ( $self, %args ) = @_;
   my ($lr, $rr) = @args{qw(lr rr)};
   my $cc   = $self->{count_col};
   my $lc   = $lr->{$cc};
   my $rc   = $rr->{$cc};
   my $diff = abs($lc - $rc);
   return unless $diff;
   $lr = { %$lr };
   delete $lr->{$cc};
   $rr = { %$rr };
   delete $rr->{$cc};
   foreach my $i ( 1 .. $diff ) {
      if ( $lc > $rc ) {
         $self->{ChangeHandler}->change('INSERT', $lr, $self->key_cols());
      }
      else {
         $self->{ChangeHandler}->change('DELETE', $rr, $self->key_cols());
      }
   }
}

# Insert into the table the specified number of times.
sub not_in_right {
   my ( $self, %args ) = @_;
   my $lr = $args{lr};
   $lr = { %$lr };
   my $cnt = delete $lr->{$self->{count_col}};
   foreach my $i ( 1 .. $cnt ) {
      $self->{ChangeHandler}->change('INSERT', $lr, $self->key_cols());
   }
}

# Delete from the table the specified number of times.
sub not_in_left {
   my ( $self, %args ) = @_;
   my $rr = $args{rr};
   $rr = { %$rr };
   my $cnt = delete $rr->{$self->{count_col}};
   foreach my $i ( 1 .. $cnt ) {
      $self->{ChangeHandler}->change('DELETE', $rr, $self->key_cols());
   }
}

sub done_with_rows {
   my ( $self ) = @_;
   $self->{done} = 1;
}

sub done {
   my ( $self ) = @_;
   return $self->{done};
}

sub key_cols {
   my ( $self ) = @_;
   return $self->{cols};
}

# Return 1 if you have changes yet to make and you don't want the TableSyncer to
# commit your transaction or release your locks.
sub pending_changes {
   my ( $self ) = @_;
   return;
}

sub _d {
   my ($package, undef, $line) = caller 0;
   @_ = map { (my $temp = $_) =~ s/\n/\n# /g; $temp; }
        map { defined $_ ? $_ : 'undef' }
        @_;
   print STDERR "# $package:$line $PID ", join(' ', @_), "\n";
}

1;
}
# ###########################################################################
# End TableSyncGroupBy package
# ###########################################################################