-# vim: ts=8:sw=4:sts=4:et
package DBIx::Class::Ordered;
use strict;
use warnings;
__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 constrainst 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 $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 $lsib = $self->next_siblings->search(
+ {},
+ { rows => 1, order_by => { '-desc' => $position_column } },
+ )->single;
+
+ return defined $lsib ? $lsib : 0;
}
=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 $self->next_siblings->count;
+ 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;
+ return $self->move_to( $self->_group_rs->count );
}
=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 $from_position = $self->_position;
+ return 0 if ( $from_position == $to_position );
+
+ my $position_column = $self->position_column;
+
+ # FIXME this needs to be wrapped in a transaction
+ {
+ my ($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
+ $self->_ordered_internal_update({ $position_column => $self->null_position_value }); # take the row out of the picture for a bit
+ $self->_shift_siblings ($direction, @between);
+ $self->_ordered_internal_update({ $position_column => $new_pos_val });
+ return 1;
+ }
+}
=head2 move_to_group
sub move_to_group {
my( $self, $to_group, $to_position ) = @_;
+ $self->throw_exception ('move_to_group() expects a group specification')
+ unless defined $to_group;
+
# if we're given a string, 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
- $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 => $new_group_count + 1 });
- }
- else {
- my @between = ($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 => $to_position });
+ if ($self->_is_in_group ($to_group) ) {
+ return 0 if not defined $to_position;
+ return $self->move_to ($to_position);
}
- return 1;
+ # FIXME this needs to be wrapped in a transaction
+ {
+ # Move to end of current group to adjust siblings
+ $self->move_last;
+
+ $self->set_inflated_columns({ %$to_group, $position_column => undef });
+ my $new_group_count = $self->_group_rs->count;
+
+ if ( not defined($to_position) or $to_position > $new_group_count) {
+ $self->set_column(
+ $position_column => $new_group_count
+ ? $self->_next_position_value ( $self->last_sibling->get_column ($position_column) ) # FIXME - no need to inflate last_sibling
+ : $self->_initial_position_value
+ );
+ }
+ else {
+ my $bumped_pos_val = $self->_position_value ($to_position);
+ my @between = ($to_position, $new_group_count);
+ $self->_shift_siblings (1, @between); #shift right
+ $self->set_column( $position_column => $bumped_pos_val );
+ }
+
+ $self->_ordered_internal_update;
+
+ return 1;
+ }
}
=head2 insert
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 = $self->last_sibling; # FIXME - no need to inflate last_sibling
+ $self->set_column(
+ $position_column => ($lsib
+ ? $self->_next_position_value ( $lsib->get_column ($position_column) )
+ : $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};
- $self->set_inflated_columns($_[0]) if @_ > 0;
+ my $upd = shift;
+ $self->set_inflated_columns($upd) if $upd;
my %changes = $self->get_dirty_columns;
$self->discard_changes;
- my $pos_col = $self->position_column;
+ my $position_column = $self->position_column;
- # if any of our grouping columns have been changed
- if (grep {$_} map {exists $changes{$_}} $self->_grouping_columns ) {
+ # if nothing group/position related changed - short circuit
+ if (not grep { exists $changes{$_} } ($self->_grouping_columns, $position_column) ) {
+ return $self->next::method( \%changes, @_ );
+ }
- # 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
+ # FIXME this needs to be wrapped in a transaction
+ {
+ # 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} = delete $changes{$col}; # don't want to pass this on to next::method
+ }
}
+
+ $self->move_to_group(
+ $new_group,
+ (exists $changes{$position_column}
+ # The FIXME bit contradicts the documentation: 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)
+ ? delete $changes{$position_column} # means there was a position change supplied with the update too
+ : $self->_position # FIXME!
+ ),
+ );
+ }
+ elsif (exists $changes{$position_column}) {
+ $self->move_to(delete $changes{$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});
+ return $self->next::method( \%changes, @_ );
}
- 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;
- $self->move_last;
- return $self->next::method( @_ );
+ # FIXME this needs to be wrapped in a transaction
+ {
+ $self->move_last;
+ return $self->next::method( @_ );
+ }
+}
+
+=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
+
+ my $num_pos = $item->_position;
+
+Returns the absolute numeric position of the current object, with the
+first object being at position 1, its sibling at position 2 and so on.
+By default simply returns the value of L</position_column>.
+
+=cut
+sub _position {
+ my $self = shift;
+
+# #the right way to do this
+# return $self->previous_siblings->count + 1;
+
+ return $self->get_column ($self->position_column);
+}
+
+=head2 _position_value
+
+ my $pos_value = $item->_position_value ( $pos )
+
+Returns the value of L</position_column> of the object at numeric
+position C<$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 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 ( $position_value )
+
+Returns a position value that would be considered C<next> with
+regards to C<$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 position in the range @between (inclusive)
+by one position as specified by $direction (left if < 0, right if > 0).
+By default simply increments/decrements each L<position_column> value
+by 1.
+
+=cut
+sub _shift_siblings {
+ my ($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 %uc = $self->result_source->unique_constraints;
+ if (grep { $_ eq $position_column } ( map { @$_ } (values %uc) ) ) {
+
+ my $rs = $shift_rs->search ({}, { order_by => { "-$ord", $position_column } } );
+ # FIXME - no need to inflate each row
+ while (my $r = $rs->next) {
+ $r->_ordered_internal_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 memebers 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 _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
+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
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;
}
+sub _ordered_internal_update {
+ my $self = shift;
+ local $self->{_ORDERED_INTERNAL_UPDATE} = 1;
+ return $self->update (@_);
+}
1;
-__END__
-
-=head1 BUGS
-=head2 Unique Constraints
+__END__
-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.
+=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
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
projects / dbsrgits/DBIx-Class.git / commitdiff