-# vim: ts=8:sw=4:sts=4:et
package DBIx::Class::Ordered;
use strict;
use warnings;
#!/use/bin/perl
use My::Item;
-
+
my $item = My::Item->create({ name=>'Matt S. Trout' });
# If using grouping_column:
my $item = My::Item->create({ name=>'Matt S. Trout', group_id=>1 });
-
+
my $rs = $item->siblings();
my @siblings = $item->siblings();
-
+
my $sibling;
$sibling = $item->first_sibling();
$sibling = $item->last_sibling();
$sibling = $item->previous_sibling();
$sibling = $item->next_sibling();
-
+
$item->move_previous();
$item->move_next();
$item->move_first();
__PACKAGE__->mk_classdata( 'grouping_column' );
+=head2 null_position_value
+
+ __PACKAGE__->null_position_value(undef);
+
+This method specifies a value of L</position_column> which B<would
+never be assigned to a row> during normal operation. When
+a row is moved, its position is set to this value temporarily, so
+that any unique constraints can not be violated. This value defaults
+to 0, which should work for all cases except when your positions do
+indeed start from 0.
+
+=cut
+
+__PACKAGE__->mk_classdata( 'null_position_value' => 0 );
+
=head2 siblings
my $rs = $item->siblings();
my @siblings = $item->siblings();
-Returns either a resultset or an array of all other objects
-excluding the one you called it on.
+Returns an B<ordered> resultset of all other objects in the same
+group excluding the one you called it on.
-=cut
+The ordering is a backwards-compatibility artifact - if you need
+a resultset with no ordering applied use L</_siblings>
+=cut
sub siblings {
- my( $self ) = @_;
- my $position_column = $self->position_column;
- my $rs = $self->result_source->resultset->search(
- {
- $position_column => { '!=' => $self->get_column($position_column) },
- $self->_grouping_clause(),
- },
- { order_by => $self->position_column },
- );
- return $rs->all() if (wantarray());
- return $rs;
+ my $self = shift;
+ return $self->_siblings->search ({}, { order_by => $self->position_column } );
}
-=head2 first_sibling
+=head2 previous_siblings
- my $sibling = $item->first_sibling();
+ my $prev_rs = $item->previous_siblings();
+ my @prev_siblings = $item->previous_siblings();
-Returns the first sibling object, or 0 if the first sibling
-is this sibling.
+Returns a resultset of all objects in the same group
+positioned before the object on which this method was called.
=cut
-
-sub first_sibling {
- my( $self ) = @_;
- return 0 if ($self->get_column($self->position_column())==1);
-
- return ($self->result_source->resultset->search(
- {
- $self->position_column => 1,
- $self->_grouping_clause(),
- },
- )->all())[0];
+sub previous_siblings {
+ my $self = shift;
+ my $position_column = $self->position_column;
+ my $position = $self->get_column ($position_column);
+ return ( defined $position
+ ? $self->_siblings->search ({ $position_column => { '<', $position } })
+ : $self->_siblings
+ );
}
-=head2 last_sibling
+=head2 next_siblings
- my $sibling = $item->last_sibling();
+ my $next_rs = $item->next_siblings();
+ my @next_siblings = $item->next_siblings();
-Returns the last sibling, or 0 if the last sibling is this
-sibling.
+Returns a resultset of all objects in the same group
+positioned after the object on which this method was called.
=cut
-
-sub last_sibling {
- my( $self ) = @_;
- my $count = $self->result_source->resultset->search({$self->_grouping_clause()})->count();
- return 0 if ($self->get_column($self->position_column())==$count);
- return ($self->result_source->resultset->search(
- {
- $self->position_column => $count,
- $self->_grouping_clause(),
- },
- )->all())[0];
+sub next_siblings {
+ my $self = shift;
+ my $position_column = $self->position_column;
+ my $position = $self->get_column ($position_column);
+ return ( defined $position
+ ? $self->_siblings->search ({ $position_column => { '>', $position } })
+ : $self->_siblings
+ );
}
=head2 previous_sibling
my $sibling = $item->previous_sibling();
-Returns the sibling that resides one position back. Returns undef
+Returns the sibling that resides one position back. Returns 0
if the current object is the first one.
=cut
sub previous_sibling {
- my( $self ) = @_;
+ my $self = shift;
my $position_column = $self->position_column;
- my $position = $self->get_column( $position_column );
- return 0 if ($position==1);
- return ($self->result_source->resultset->search(
- {
- $position_column => $position - 1,
- $self->_grouping_clause(),
- }
- )->all())[0];
+
+ my $psib = $self->previous_siblings->search(
+ {},
+ { rows => 1, order_by => { '-desc' => $position_column } },
+ )->single;
+
+ return defined $psib ? $psib : 0;
+}
+
+=head2 first_sibling
+
+ my $sibling = $item->first_sibling();
+
+Returns the first sibling object, or 0 if the first sibling
+is this sibling.
+
+=cut
+
+sub first_sibling {
+ my $self = shift;
+ my $position_column = $self->position_column;
+
+ my $fsib = $self->previous_siblings->search(
+ {},
+ { rows => 1, order_by => { '-asc' => $position_column } },
+ )->single;
+
+ return defined $fsib ? $fsib : 0;
}
=head2 next_sibling
my $sibling = $item->next_sibling();
-Returns the sibling that resides one position forward. Returns undef
+Returns the sibling that resides one position forward. Returns 0
if the current object is the last one.
=cut
sub next_sibling {
- my( $self ) = @_;
+ my $self = shift;
+ my $position_column = $self->position_column;
+ my $nsib = $self->next_siblings->search(
+ {},
+ { rows => 1, order_by => { '-asc' => $position_column } },
+ )->single;
+
+ return defined $nsib ? $nsib : 0;
+}
+
+=head2 last_sibling
+
+ my $sibling = $item->last_sibling();
+
+Returns the last sibling, or 0 if the last sibling is this
+sibling.
+
+=cut
+
+sub last_sibling {
+ my $self = shift;
+ my $position_column = $self->position_column;
+ my $lsib = $self->next_siblings->search(
+ {},
+ { rows => 1, order_by => { '-desc' => $position_column } },
+ )->single;
+
+ return defined $lsib ? $lsib : 0;
+}
+
+# an optimized method to get the last sibling position value without inflating a row object
+sub _last_sibling_posval {
+ my $self = shift;
my $position_column = $self->position_column;
- my $position = $self->get_column( $position_column );
- my $count = $self->result_source->resultset->search({$self->_grouping_clause()})->count();
- return 0 if ($position==$count);
- return ($self->result_source->resultset->search(
- {
- $position_column => $position + 1,
- $self->_grouping_clause(),
- },
- )->all())[0];
+
+ my $cursor = $self->next_siblings->search(
+ {},
+ { rows => 1, order_by => { '-desc' => $position_column }, select => $position_column },
+ )->cursor;
+
+ my ($pos) = $cursor->next;
+ return $pos;
}
=head2 move_previous
=cut
sub move_previous {
- my( $self ) = @_;
- my $position = $self->get_column( $self->position_column() );
- return $self->move_to( $position - 1 );
+ my $self = shift;
+ return $self->move_to ($self->_position - 1);
}
=head2 move_next
=cut
sub move_next {
- my( $self ) = @_;
- my $position = $self->get_column( $self->position_column() );
- my $count = $self->result_source->resultset->search({$self->_grouping_clause()})->count();
- return 0 if ($position==$count);
- return $self->move_to( $position + 1 );
+ my $self = shift;
+ return 0 unless defined $self->_last_sibling_posval; # quick way to check for no more siblings
+ return $self->move_to ($self->_position + 1);
}
=head2 move_first
=cut
sub move_first {
- my( $self ) = @_;
- return $self->move_to( 1 );
+ return shift->move_to( 1 );
}
=head2 move_last
=cut
sub move_last {
- my( $self ) = @_;
- my $count = $self->result_source->resultset->search({$self->_grouping_clause()})->count();
- return $self->move_to( $count );
+ my $self = shift;
+ my $last_posval = $self->_last_sibling_posval;
+
+ return 0 unless defined $last_posval;
+
+ return $self->move_to( $self->_position_from_value ($last_posval) );
}
=head2 move_to
sub move_to {
my( $self, $to_position ) = @_;
- my $position_column = $self->position_column;
- my $from_position = $self->get_column( $position_column );
return 0 if ( $to_position < 1 );
- return 0 if ( $from_position==$to_position );
- my @between = (
- ( $from_position < $to_position )
- ? ( $from_position+1, $to_position )
- : ( $to_position, $from_position-1 )
- );
- my $rs = $self->result_source->resultset->search({
- $position_column => { -between => [ @between ] },
- $self->_grouping_clause(),
- });
- my $op = ($from_position>$to_position) ? '+' : '-';
- $rs->update({ $position_column => \"$position_column $op 1" }); #" Sorry, GEdit bug
- $self->{_ORDERED_INTERNAL_UPDATE} = 1;
- $self->update({ $position_column => $to_position });
- return 1;
-}
+ my $position_column = $self->position_column;
+ my $guard;
+
+ if ($self->is_column_changed ($position_column) ) {
+ # something changed our position, we have no idea where we
+ # used to be - requery without using discard_changes
+ # (we need only a specific column back)
+
+ $guard = $self->result_source->schema->txn_scope_guard;
+
+ my $cursor = $self->result_source->resultset->search(
+ $self->ident_condition,
+ { select => $position_column },
+ )->cursor;
+
+ my ($pos) = $cursor->next;
+ $self->$position_column ($pos);
+ delete $self->{_dirty_columns}{$position_column};
+ }
+
+ my $from_position = $self->_position;
+
+ if ( $from_position == $to_position ) { # FIXME this will not work for non-numeric order
+ $guard->commit if $guard;
+ return 0;
+ }
+
+ $guard ||= $self->result_source->schema->txn_scope_guard;
+
+ my ($direction, @between);
+ if ( $from_position < $to_position ) {
+ $direction = -1;
+ @between = map { $self->_position_value ($_) } ( $from_position + 1, $to_position );
+ }
+ else {
+ $direction = 1;
+ @between = map { $self->_position_value ($_) } ( $to_position, $from_position - 1 );
+ }
+
+ my $new_pos_val = $self->_position_value ($to_position); # record this before the shift
+
+ # we need to null-position the moved row if the position column is part of a constraint
+ if (grep { $_ eq $position_column } ( map { @$_ } (values %{{ $self->result_source->unique_constraints }} ) ) ) {
+ $self->_ordered_internal_update({ $position_column => $self->null_position_value });
+ }
+
+ $self->_shift_siblings ($direction, @between);
+ $self->_ordered_internal_update({ $position_column => $new_pos_val });
+
+ $guard->commit;
+ return 1;
+}
=head2 move_to_group
sub move_to_group {
my( $self, $to_group, $to_position ) = @_;
- # if we're given a string, turn it into a hashref
+ # if we're given a single value, turn it into a hashref
unless (ref $to_group eq 'HASH') {
- $to_group = {($self->_grouping_columns)[0] => $to_group};
+ my @gcols = $self->_grouping_columns;
+
+ $self->throw_exception ('Single group supplied for a multi-column group identifier') if @gcols > 1;
+ $to_group = {$gcols[0] => $to_group};
}
my $position_column = $self->position_column;
- #my @grouping_columns = $self->_grouping_columns;
- return 0 if ( ! defined($to_group) );
return 0 if ( defined($to_position) and $to_position < 1 );
- return 0 if ( $self->_is_in_group($to_group)
- and ((not defined($to_position))
- or (defined($to_position) and $self->$position_column==$to_position)
- )
- );
- # Move to end of current group and adjust siblings
+ # check if someone changed the _grouping_columns - this will
+ # prevent _is_in_group working, so we need to requery the db
+ # for the original values
+ my (@dirty_cols, %values, $guard);
+ for ($self->_grouping_columns) {
+ $values{$_} = $self->get_column ($_);
+ push @dirty_cols, $_ if $self->is_column_changed ($_);
+ }
+
+ # re-query only the dirty columns, and restore them on the
+ # object (subsequent code will update them to the correct
+ # after-move values)
+ if (@dirty_cols) {
+ $guard = $self->result_source->schema->txn_scope_guard;
+
+ my $cursor = $self->result_source->resultset->search(
+ $self->ident_condition,
+ { select => \@dirty_cols },
+ )->cursor;
+
+ my @original_values = $cursor->next;
+ $self->set_inflated_columns ({ %values, map { $_ => shift @original_values } (@dirty_cols) });
+ delete $self->{_dirty_columns}{$_} for (@dirty_cols);
+ }
+
+ if ($self->_is_in_group ($to_group) ) {
+ my $ret;
+ if (defined $to_position) {
+ $ret = $self->move_to ($to_position);
+ }
+
+ $guard->commit if $guard;
+ return $ret||0;
+ }
+
+ $guard ||= $self->result_source->schema->txn_scope_guard;
+
+ # Move to end of current group to adjust siblings
$self->move_last;
- $self->set_columns($to_group);
- my $new_group_count = $self->result_source->resultset->search({$self->_grouping_clause()})->count();
- if (!defined($to_position) or $to_position > $new_group_count) {
- $self->{_ORDERED_INTERNAL_UPDATE} = 1;
- $self->update({ $position_column => $new_group_count + 1 });
+ $self->set_inflated_columns({ %$to_group, $position_column => undef });
+ my $new_group_last_posval = $self->_last_sibling_posval;
+ my $new_group_last_position = $self->_position_from_value (
+ $new_group_last_posval
+ );
+
+ if ( not defined($to_position) or $to_position > $new_group_last_position) {
+ $self->set_column(
+ $position_column => $new_group_last_position
+ ? $self->_next_position_value ( $new_group_last_posval )
+ : $self->_initial_position_value
+ );
}
else {
- my @between = ($to_position, $new_group_count);
-
- my $rs = $self->result_source->resultset->search({
- $position_column => { -between => [ @between ] },
- $self->_grouping_clause(),
- });
- $rs->update({ $position_column => \"$position_column + 1" }); #"
- $self->{_ORDERED_INTERNAL_UPDATE} = 1;
- $self->update({ $position_column => $to_position });
+ my $bumped_pos_val = $self->_position_value ($to_position);
+ my @between = map { $self->_position_value ($_) } ($to_position, $new_group_last_position);
+ $self->_shift_siblings (1, @between); #shift right
+ $self->set_column( $position_column => $bumped_pos_val );
}
+ $self->_ordered_internal_update;
+
+ $guard->commit;
+
return 1;
}
sub insert {
my $self = shift;
my $position_column = $self->position_column;
- $self->set_column( $position_column => $self->result_source->resultset->search( {$self->_grouping_clause()} )->count()+1 )
- if (!$self->get_column($position_column));
+
+ unless ($self->get_column($position_column)) {
+ my $lsib_posval = $self->_last_sibling_posval;
+ $self->set_column(
+ $position_column => (defined $lsib_posval
+ ? $self->_next_position_value ( $lsib_posval )
+ : $self->_initial_position_value
+ )
+ );
+ }
+
return $self->next::method( @_ );
}
sub update {
my $self = shift;
- if ($self->{_ORDERED_INTERNAL_UPDATE}) {
- delete $self->{_ORDERED_INTERNAL_UPDATE};
- return $self->next::method( @_ );
+ # this is set by _ordered_internal_update()
+ return $self->next::method(@_) if $self->{_ORDERED_INTERNAL_UPDATE};
+
+ my $position_column = $self->position_column;
+ my @ordering_columns = ($self->_grouping_columns, $position_column);
+
+
+ # these steps are necessary to keep the external appearance of
+ # ->update($upd) so that other things overloading update() will
+ # work properly
+ my %original_values = $self->get_columns;
+ my %existing_changes = $self->get_dirty_columns;
+
+ # See if any of the *supplied* changes would affect the ordering
+ # The reason this is so contrived, is that we want to leverage
+ # the datatype aware value comparing, while at the same time
+ # keep the original value intact (it will be updated later by the
+ # corresponding routine)
+
+ my %upd = %{shift || {}};
+ my %changes = %existing_changes;
+
+ for (@ordering_columns) {
+ next unless exists $upd{$_};
+
+ # we do not want to keep propagating this to next::method
+ # as it will be a done deal by the time get there
+ my $value = delete $upd{$_};
+ $self->set_inflated_columns ({ $_ => $value });
+
+ # see if an update resulted in a dirty column
+ # it is important to preserve the old value, as it
+ # will be needed to carry on a successfull move()
+ # operation without re-querying the database
+ if ($self->is_column_changed ($_) && not exists $existing_changes{$_}) {
+ $changes{$_} = $value;
+ $self->set_inflated_columns ({ $_ => $original_values{$_} });
+ delete $self->{_dirty_columns}{$_};
+ }
}
- $self->set_inflated_columns($_[0]) if @_ > 0;
- my %changes = $self->get_dirty_columns;
- $self->discard_changes;
+ # if nothing group/position related changed - short circuit
+ if (not grep { exists $changes{$_} } ( @ordering_columns ) ) {
+ return $self->next::method( \%upd, @_ );
+ }
- my $pos_col = $self->position_column;
+ {
+ my $guard = $self->result_source->schema->txn_scope_guard;
- # if any of our grouping columns have been changed
- if (grep {$_} map {exists $changes{$_}} $self->_grouping_columns ) {
+ # if any of our grouping columns have been changed
+ if (grep { exists $changes{$_} } ($self->_grouping_columns) ) {
- # create new_group by taking the current group and inserting changes
- my $new_group = {$self->_grouping_clause};
- foreach my $col (keys %$new_group) {
- if (exists $changes{$col}) {
- $new_group->{$col} = $changes{$col};
- delete $changes{$col}; # don't want to pass this on to next::method
+ # create new_group by taking the current group and inserting changes
+ my $new_group = {$self->_grouping_clause};
+ foreach my $col (keys %$new_group) {
+ $new_group->{$col} = $changes{$col} if exists $changes{$col};
}
+
+ $self->move_to_group(
+ $new_group,
+ (exists $changes{$position_column}
+ # The FIXME bit contradicts the documentation: POD states that
+ # when changing groups without supplying explicit positions in
+ # move_to_group(), we push the item to the end of the group.
+ # However when I was rewriting this, the position from the old
+ # group was clearly passed to the new one
+ # Probably needs to go away (by ribasushi)
+ ? $changes{$position_column} # means there was a position change supplied with the update too
+ : $self->_position # FIXME! (replace with undef)
+ ),
+ );
+ }
+ elsif (exists $changes{$position_column}) {
+ $self->move_to($changes{$position_column});
}
- $self->move_to_group(
- $new_group,
- exists($changes{$pos_col}) ? delete($changes{$pos_col}) : $self->get_column ($pos_col)
- );
- }
- elsif (exists $changes{$pos_col}) {
- $self->move_to(delete $changes{$pos_col});
+ my @res;
+ my $want = wantarray();
+ if (not defined $want) {
+ $self->next::method( \%upd, @_ );
+ }
+ elsif ($want) {
+ @res = $self->next::method( \%upd, @_ );
+ }
+ else {
+ $res[0] = $self->next::method( \%upd, @_ );
+ }
+
+ $guard->commit;
+ return $want ? @res : $res[0];
}
- return $self->next::method( \%changes );
}
=head2 delete
Overrides the DBIC delete() method by first moving the object
-to the last position, then deleting it, thus ensuring the
+to the last position, then deleting it, thus ensuring the
integrity of the positions.
=cut
sub delete {
my $self = shift;
+
+ my $guard = $self->result_source->schema->txn_scope_guard;
+
$self->move_last;
- return $self->next::method( @_ );
+
+ my @res;
+ my $want = wantarray();
+ if (not defined $want) {
+ $self->next::method( @_ );
+ }
+ elsif ($want) {
+ @res = $self->next::method( @_ );
+ }
+ else {
+ $res[0] = $self->next::method( @_ );
+ }
+
+ $guard->commit;
+ return $want ? @res : $res[0];
+}
+
+=head1 METHODS FOR EXTENDING ORDERED
+
+You would want to override the methods below if you use sparse
+(non-linear) or non-numeric position values. This can be useful
+if you are working with preexisting non-normalised position data,
+or if you need to work with materialized path columns.
+
+=head2 _position_from_value
+
+ my $num_pos = $item->_position_from_value ( $pos_value )
+
+Returns the B<absolute numeric position> of an object with a B<position
+value> set to C<$pos_value>. By default simply returns C<$pos_value>.
+
+=cut
+sub _position_from_value {
+ my ($self, $val) = @_;
+
+ return 0 unless defined $val;
+
+# #the right way to do this
+# return $self -> _group_rs
+# -> search({ $self->position_column => { '<=', $val } })
+# -> count
+
+ return $val;
+}
+
+=head2 _position_value
+
+ my $pos_value = $item->_position_value ( $pos )
+
+Returns the B<value> of L</position_column> of the object at numeric
+position C<$pos>. By default simply returns C<$pos>.
+
+=cut
+sub _position_value {
+ my ($self, $pos) = @_;
+
+# #the right way to do this (not optimized)
+# my $position_column = $self->position_column;
+# return $self -> _group_rs
+# -> search({}, { order_by => $position_column })
+# -> slice ( $pos - 1)
+# -> single
+# -> get_column ($position_column);
+
+ return $pos;
+}
+
+=head2 _initial_position_value
+
+ __PACKAGE__->_initial_position_value(0);
+
+This method specifies a B<value> of L</position_column> which is assigned
+to the first inserted element of a group, if no value was supplied at
+insertion time. All subsequent values are derived from this one by
+L</_next_position_value> below. Defaults to 1.
+
+=cut
+
+__PACKAGE__->mk_classdata( '_initial_position_value' => 1 );
+
+=head2 _next_position_value
+
+ my $new_value = $item->_next_position_value ( $position_value )
+
+Returns a position B<value> that would be considered C<next> with
+regards to C<$position_value>. Can be pretty much anything, given
+that C<< $position_value < $new_value >> where C<< < >> is the
+SQL comparison operator (usually works fine on strings). The
+default method expects C<$position_value> to be numeric, and
+returns C<$position_value + 1>
+
+=cut
+sub _next_position_value {
+ return $_[1] + 1;
+}
+
+=head2 _shift_siblings
+
+ $item->_shift_siblings ($direction, @between)
+
+Shifts all siblings with B<positions values> in the range @between
+(inclusive) by one position as specified by $direction (left if < 0,
+ right if > 0). By default simply increments/decrements each
+L<position_column> value by 1, doing so in a way as to not violate
+any existing constraints.
+
+Note that if you override this method and have unique constraints
+including the L<position_column> the shift is not a trivial task.
+Refer to the implementation source of the default method for more
+information.
+
+=cut
+sub _shift_siblings {
+ my ($self, $direction, @between) = @_;
+ return 0 unless $direction;
+
+ my $position_column = $self->position_column;
+
+ my ($op, $ord);
+ if ($direction < 0) {
+ $op = '-';
+ $ord = 'asc';
+ }
+ else {
+ $op = '+';
+ $ord = 'desc';
+ }
+
+ my $shift_rs = $self->_group_rs-> search ({ $position_column => { -between => \@between } });
+
+ # some databases (sqlite) are dumb and can not do a blanket
+ # increment/decrement. So what we do here is check if the
+ # position column is part of a unique constraint, and do a
+ # one-by-one update if this is the case
+
+ my $rsrc = $self->result_source;
+
+ if (grep { $_ eq $position_column } ( map { @$_ } (values %{{ $rsrc->unique_constraints }} ) ) ) {
+
+ my @pcols = $rsrc->primary_columns;
+ my $cursor = $shift_rs->search ({}, { order_by => { "-$ord", $position_column }, columns => \@pcols } )->cursor;
+ my $rs = $self->result_source->resultset;
+
+ while (my @pks = $cursor->next ) {
+
+ my $cond;
+ for my $i (0.. $#pcols) {
+ $cond->{$pcols[$i]} = $pks[$i];
+ }
+
+ $rs->search($cond)->update ({ $position_column => \ "$position_column $op 1" } );
+ }
+ }
+ else {
+ $shift_rs->update ({ $position_column => \ "$position_column $op 1" } );
+ }
}
=head1 PRIVATE METHODS
These methods are used internally. You should never have the
need to use them.
+=head2 _group_rs
+
+This method returns a resultset containing all members of the row
+group (including the row itself).
+
+=cut
+sub _group_rs {
+ my $self = shift;
+ return $self->result_source->resultset->search({$self->_grouping_clause()});
+}
+
+=head2 _siblings
+
+Returns an unordered resultset of all objects in the same group
+excluding the object you called this method on.
+
+=cut
+sub _siblings {
+ my $self = shift;
+ my $position_column = $self->position_column;
+ return $self->_group_rs->search(
+ { $position_column => { '!=' => $self->get_column($position_column) } },
+ );
+}
+
+=head2 _position
+
+ my $num_pos = $item->_position;
+
+Returns the B<absolute numeric position> of the current object, with the
+first object being at position 1, its sibling at position 2 and so on.
+
+=cut
+sub _position {
+ my $self = shift;
+ return $self->_position_from_value ($self->get_column ($self->position_column) );
+}
+
=head2 _grouping_clause
-This method returns one or more name=>value pairs for limiting a search
-by the grouping column(s). If the grouping column is not
-defined then this will return an empty list.
+This method returns one or more name=>value pairs for limiting a search
+by the grouping column(s). If the grouping column is not defined then
+this will return an empty list.
=cut
sub _grouping_clause {
return map { $_ => $self->get_column($_) } $self->_grouping_columns();
}
-
-
=head2 _get_grouping_columns
Returns a list of the column names used for grouping, regardless of whether
}
}
-
-
-=head2 _is_in_group($other)
+=head2 _is_in_group
$item->_is_in_group( {user => 'fred', list => 'work'} )
Returns true if the object is in the group represented by hashref $other
+
=cut
sub _is_in_group {
my ($self, $other) = @_;
my $current = {$self->_grouping_clause};
- return 0 unless (ref $other eq 'HASH') and (keys %$current == keys %$other);
+
+ no warnings qw/uninitialized/;
+
+ return 0 if (
+ join ("\x00", sort keys %$current)
+ ne
+ join ("\x00", sort keys %$other)
+ );
for my $key (keys %$current) {
- return 0 unless exists $other->{$key};
return 0 if $current->{$key} ne $other->{$key};
}
return 1;
}
+=head2 _ordered_internal_update
-1;
-__END__
+This is a short-circuited method, that is used internally by this
+module to update positioning values in isolation (i.e. without
+triggering any of the positioning integrity code).
-=head1 BUGS
+Some day you might get confronted by datasets that have ambiguous
+positioning data (e.g. duplicate position values within the same group,
+in a table without unique constraints). When manually fixing such data
+keep in mind that you can not invoke L<DBIx::Class::Row/update> like
+you normally would, as it will get confused by the wrong data before
+having a chance to update the ill-defined row. If you really know what
+you are doing use this method which bypasses any hooks introduced by
+this module.
-=head2 Unique Constraints
+=cut
-Unique indexes and constraints on the position column are not
-supported at this time. It would be make sense to support them,
-but there are some unexpected database issues that make this
-hard to do. The main problem from the author's view is that
-SQLite (the DB engine that we use for testing) does not support
-ORDER BY on updates.
+sub _ordered_internal_update {
+ my $self = shift;
+ local $self->{_ORDERED_INTERNAL_UPDATE} = 1;
+ return $self->update (@_);
+}
+
+1;
+
+__END__
+
+=head1 CAVEATS
=head2 Race Condition on Insert
If a position is not specified for an insert than a position
-will be chosen based on COUNT(*)+1. But, it first selects the
-count, and then inserts the record. The space of time between select
-and insert introduces a race condition. To fix this we need the
-ability to lock tables in DBIC. I've added an entry in the TODO
-about this.
+will be chosen based either on L</_initial_position_value> or
+L</_next_position_value>, depending if there are already some
+items in the current group. The space of time between the
+necessary selects and insert introduces a race condition.
+Having unique constraints on your position/group columns,
+and using transactions (see L<DBIx::Class::Storage/txn_do>)
+will prevent such race conditions going undetected.
=head2 Multiple Moves
-Be careful when issueing move_* methods to multiple objects. If
+Be careful when issuing move_* methods to multiple objects. If
you've pre-loaded the objects then when you move one of the objects
the position of the other object will not reflect their new value
-until you reload them from the database.
+until you reload them from the database - see
+L<DBIx::Class::Row/discard_changes>.
There are times when you will want to move objects as groups, such
-as changeing the parent of several objects at once - this directly
+as changing the parent of several objects at once - this directly
conflicts with this problem. One solution is for us to write a
ResultSet class that supports a parent() method, for example. Another
solution is to somehow automagically modify the objects that exist
in the current object's result set to have the new position value.
+=head2 Default Values
+
+Using a database defined default_value on one of your group columns
+could result in the position not being assigned correctly.
+
=head1 AUTHOR
-Aran Deltac <bluefeet@cpan.org>
+ Original code framework
+ Aran Deltac <bluefeet@cpan.org>
+
+ Constraints support and code generalisation
+ Peter Rabbitson <ribasushi@cpan.org>
=head1 LICENSE
projects / dbsrgits/DBIx-Class.git / blobdiff