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[dbsrgits/DBIx-Class-Historic.git] / lib / DBIx / Class / SQLAHacks / OracleJoins.pm

package # Hide from PAUSE
  DBIx::Class::SQLAHacks::OracleJoins;

use base qw( DBIx::Class::SQLAHacks );
use Carp::Clan qw/^DBIx::Class|^SQL::Abstract/;

sub select {
  my ($self, $table, $fields, $where, $order, @rest) = @_;

  if (ref($table) eq 'ARRAY') {
    $where = $self->_oracle_joins($where, @{ $table });
  }

  return $self->SUPER::select($table, $fields, $where, $order, @rest);
}

sub _recurse_from {
  my ($self, $from, @join) = @_;

  my @sqlf = $self->_make_as($from);

  foreach my $j (@join) {
    my ($to, $on) = @{ $j };

    if (ref $to eq 'ARRAY') {
      push (@sqlf, $self->_recurse_from(@{ $to }));
    }
    else {
      push (@sqlf, $self->_make_as($to));
    }
  }

  return join q{, }, @sqlf;
}

sub _oracle_joins {
  my ($self, $where, $from, @join) = @_;
  my $join_where = {};
  $self->_recurse_oracle_joins($join_where, $from, @join);
  if (keys %$join_where) {
    if (!defined($where)) {
      $where = $join_where;
    } else {
      if (ref($where) eq 'ARRAY') {
        $where = { -or => $where };
      }
      $where = { -and => [ $join_where, $where ] };
    }
  }
  return $where;
}

sub _recurse_oracle_joins {
  my ($self, $where, $from, @join) = @_;

  foreach my $j (@join) {
    my ($to, $on) = @{ $j };

    if (ref $to eq 'ARRAY') {
      $self->_recurse_oracle_joins($where, @{ $to });
    }

    my $to_jt      = ref $to eq 'ARRAY' ? $to->[0] : $to;
    my $left_join  = q{};
    my $right_join = q{};

    if (ref $to_jt eq 'HASH' and exists $to_jt->{-join_type}) {
      #TODO: Support full outer joins -- this would happen much earlier in
      #the sequence since oracle 8's full outer join syntax is best
      #described as INSANE.
      croak "Can't handle full outer joins in Oracle 8 yet!\n"
        if $to_jt->{-join_type} =~ /full/i;

      $left_join  = q{(+)} if $to_jt->{-join_type} =~ /left/i
        && $to_jt->{-join_type} !~ /inner/i;

      $right_join = q{(+)} if $to_jt->{-join_type} =~ /right/i
        && $to_jt->{-join_type} !~ /inner/i;
    }

    foreach my $lhs (keys %{ $on }) {
      $where->{$lhs . $left_join} = \"= $on->{ $lhs }$right_join";
    }
  }
}

1;

=pod

=head1 NAME

DBIx::Class::SQLAHacks::OracleJoins - Pre-ANSI Joins-via-Where-Clause Syntax

=head1 PURPOSE

This module was originally written to support Oracle < 9i where ANSI joins
weren't supported at all, but became the module for Oracle >= 8 because
Oracle's optimising of ANSI joins is horrible.  (See:
http://scsys.co.uk:8001/7495)

=head1 SYNOPSIS

Not intended for use directly; used as the sql_maker_class for schemas and components.

=head1 DESCRIPTION

Implements pre-ANSI joins specified in the where clause.  Instead of:

    SELECT x FROM y JOIN z ON y.id = z.id

It will write:

    SELECT x FROM y, z WHERE y.id = z.id

It should properly support left joins, and right joins.  Full outer joins are
not possible due to the fact that Oracle requires the entire query be written
to union the results of a left and right join, and by the time this module is
called to create the where query and table definition part of the sql query,
it's already too late.

=head1 METHODS

=over

=item select ($\@$;$$@)

Replaces DBIx::Class::SQLAHacks's select() method, which calls _oracle_joins()
to modify the column and table list before calling SUPER::select().

=item _recurse_from ($$\@)

Recursive subroutine that builds the table list.

=item _oracle_joins ($$$@)

Creates the left/right relationship in the where query.

=back

=head1 BUGS

Does not support full outer joins.
Probably lots more.

=head1 SEE ALSO

=over

=item L<DBIx::Class::Storage::DBI::Oracle::WhereJoins> - Storage class using this

=item L<DBIx::Class::SQLAHacks> - Parent module

=item L<DBIx::Class> - Duh

=back

=head1 AUTHOR

Justin Wheeler C<< <jwheeler@datademons.com> >>

=head1 CONTRIBUTORS

David Jack Olrik C<< <djo@cpan.org> >>

=head1 LICENSE

This module is licensed under the same terms as Perl itself.

=cut