1 package DBIx::Class::ResultSetColumn;
4 use base 'DBIx::Class';
9 DBIx::Class::ResultSetColumn - helpful methods for messing
10 with a single column of the resultset
14 $rs = $schema->resultset('CD')->search({ artist => 'Tool' });
15 $rs_column = $rs->get_column('year');
16 $max_year = $rs_column->max; #returns latest year
20 A convenience class used to perform operations on a specific column of
29 my $obj = DBIx::Class::ResultSetColumn->new($rs, $column);
31 Creates a new resultset column object from the resultset and column
32 passed as params. Used internally by L<DBIx::Class::ResultSet/get_column>.
37 my ($class, $rs, $column) = @_;
38 $class = ref $class if ref $class;
40 $rs->throw_exception("column must be supplied") unless $column;
42 my $orig_attrs = $rs->_resolved_attrs;
43 my $new_parent_rs = $rs->search_rs;
45 # prefetch causes additional columns to be fetched, but we can not just make a new
46 # rs via the _resolved_attrs trick - we need to retain the separation between
47 # +select/+as and select/as. At the same time we want to preserve any joins that the
48 # prefetch would otherwise generate.
50 my $new_attrs = $new_parent_rs->{attrs} ||= {};
51 $new_attrs->{join} = $rs->_merge_attr( delete $new_attrs->{join}, delete $new_attrs->{prefetch} );
53 # If $column can be found in the 'as' list of the parent resultset, use the
54 # corresponding element of its 'select' list (to keep any custom column
55 # definition set up with 'select' or '+select' attrs), otherwise use $column
56 # (to create a new column definition on-the-fly).
58 my $as_list = $orig_attrs->{as} || [];
59 my $select_list = $orig_attrs->{select} || [];
60 my $as_index = List::Util::first { ($as_list->[$_] || "") eq $column } 0..$#$as_list;
61 my $select = defined $as_index ? $select_list->[$as_index] : $column;
63 # {collapse} would mean a has_many join was injected, which in turn means
64 # we need to group IF WE CAN (only if the column in question is unique)
65 if (!$new_attrs->{group_by} && keys %{$orig_attrs->{collapse}}) {
67 # scan for a constraint that would contain our column only - that'd be proof
69 my $constraints = { $rs->result_source->unique_constraints };
70 for my $constraint_columns ( values %$constraints ) {
72 next unless @$constraint_columns == 1;
74 my $col = $constraint_columns->[0];
75 my $fqcol = join ('.', $new_attrs->{alias}, $col);
77 if ($col eq $select or $fqcol eq $select) {
78 $new_attrs->{group_by} = [ $select ];
84 my $new = bless { _select => $select, _as => $column, _parent_resultset => $new_parent_rs }, $class;
88 =head2 as_query (EXPERIMENTAL)
94 =item Return Value: \[ $sql, @bind ]
98 Returns the SQL query and bind vars associated with the invocant.
100 This is generally used as the RHS for a subquery.
102 B<NOTE>: This feature is still experimental.
106 sub as_query { return shift->_resultset->as_query(@_) }
112 =item Arguments: none
114 =item Return Value: $value
118 Returns the next value of the column in the resultset (or C<undef> if
121 Much like L<DBIx::Class::ResultSet/next> but just returning the
129 # using cursor so we don't inflate anything
130 my ($row) = $self->_resultset->cursor->next;
139 =item Arguments: none
141 =item Return Value: @values
145 Returns all values of the column in the resultset (or C<undef> if
148 Much like L<DBIx::Class::ResultSet/all> but returns values rather
156 # using cursor so we don't inflate anything
157 return map { $_->[0] } $self->_resultset->cursor->all;
164 =item Arguments: none
166 =item Return Value: $self
170 Resets the underlying resultset's cursor, so you can iterate through the
171 elements of the column again.
173 Much like L<DBIx::Class::ResultSet/reset>.
179 $self->_resultset->cursor->reset;
187 =item Arguments: none
189 =item Return Value: $value
193 Resets the underlying resultset and returns the next value of the column in the
194 resultset (or C<undef> if there is none).
196 Much like L<DBIx::Class::ResultSet/first> but just returning the one value.
203 # using cursor so we don't inflate anything
204 $self->_resultset->cursor->reset;
205 my ($row) = $self->_resultset->cursor->next;
214 =item Arguments: none
216 =item Return Value: $value
220 Much like L<DBIx::Class::ResultSet/single> fetches one and only one column
221 value using the cursor directly. If additional rows are present a warning
222 is issued before discarding the cursor.
229 my $attrs = $self->_resultset->_resolved_attrs;
230 my ($row) = $self->_resultset->result_source->storage->select_single(
231 $attrs->{from}, $attrs->{select}, $attrs->{where}, $attrs
241 =item Arguments: none
243 =item Return Value: $lowest_value
247 my $first_year = $year_col->min();
249 Wrapper for ->func. Returns the lowest value of the column in the
250 resultset (or C<undef> if there are none).
255 return shift->func('MIN');
262 =item Arguments: none
264 =item Return Value: $resultset
268 my $rs = $year_col->min_rs();
270 Wrapper for ->func_rs for function MIN().
274 sub min_rs { return shift->func_rs('MIN') }
280 =item Arguments: none
282 =item Return Value: $highest_value
286 my $last_year = $year_col->max();
288 Wrapper for ->func. Returns the highest value of the column in the
289 resultset (or C<undef> if there are none).
294 return shift->func('MAX');
301 =item Arguments: none
303 =item Return Value: $resultset
307 my $rs = $year_col->max_rs();
309 Wrapper for ->func_rs for function MAX().
313 sub max_rs { return shift->func_rs('MAX') }
319 =item Arguments: none
321 =item Return Value: $sum_of_values
325 my $total = $prices_col->sum();
327 Wrapper for ->func. Returns the sum of all the values in the column of
328 the resultset. Use on varchar-like columns at your own risk.
333 return shift->func('SUM');
340 =item Arguments: none
342 =item Return Value: $resultset
346 my $rs = $year_col->sum_rs();
348 Wrapper for ->func_rs for function SUM().
352 sub sum_rs { return shift->func_rs('SUM') }
358 =item Arguments: $function
360 =item Return Value: $function_return_value
364 $rs = $schema->resultset("CD")->search({});
365 $length = $rs->get_column('title')->func('LENGTH');
367 Runs a query using the function on the column and returns the
368 value. Produces the following SQL:
370 SELECT LENGTH( title ) FROM cd me
375 my ($self,$function) = @_;
376 my $cursor = $self->func_rs($function)->cursor;
379 return map { $_->[ 0 ] } $cursor->all;
382 return ( $cursor->next )[ 0 ];
389 =item Arguments: $function
391 =item Return Value: $resultset
395 Creates the resultset that C<func()> uses to run its query.
400 my ($self,$function) = @_;
401 return $self->{_parent_resultset}->search(
403 select => {$function => $self->{_select}},
404 as => [$self->{_as}],
409 =head2 throw_exception
411 See L<DBIx::Class::Schema/throw_exception> for details.
415 sub throw_exception {
417 if (ref $self && $self->{_parent_resultset}) {
418 $self->{_parent_resultset}->throw_exception(@_)
428 # Return Value: $resultset
430 # $year_col->_resultset->next
432 # Returns the underlying resultset. Creates it from the parent resultset if
438 return $self->{_resultset} ||= $self->{_parent_resultset}->search(undef,
440 select => [$self->{_select}],
450 Luke Saunders <luke.saunders@gmail.com>
456 You may distribute this code under the same terms as Perl itself.