As clear as it gets
[dbsrgits/DBIx-Class-Historic.git] / lib / DBIx / Class / ResultSetColumn.pm
CommitLineData
2bb7b40b 1package DBIx::Class::ResultSetColumn;
1a58752c 2
2bb7b40b 3use strict;
4use warnings;
1a58752c 5
2bb7b40b 6use base 'DBIx::Class';
1a58752c 7
722c0140 8use Carp::Clan qw/^DBIx::Class/;
1a58752c 9use DBIx::Class::Exception;
66521001 10use List::Util;
2bb7b40b 11
12=head1 NAME
13
14 DBIx::Class::ResultSetColumn - helpful methods for messing
15 with a single column of the resultset
16
17=head1 SYNOPSIS
18
19 $rs = $schema->resultset('CD')->search({ artist => 'Tool' });
20 $rs_column = $rs->get_column('year');
21 $max_year = $rs_column->max; #returns latest year
22
23=head1 DESCRIPTION
24
eb98561c 25A convenience class used to perform operations on a specific column of
26a resultset.
2bb7b40b 27
28=cut
29
30=head1 METHODS
31
32=head2 new
33
34 my $obj = DBIx::Class::ResultSetColumn->new($rs, $column);
35
eb98561c 36Creates a new resultset column object from the resultset and column
37passed as params. Used internally by L<DBIx::Class::ResultSet/get_column>.
2bb7b40b 38
39=cut
40
41sub new {
42 my ($class, $rs, $column) = @_;
43 $class = ref $class if ref $class;
7ae9706c 44
45 $rs->throw_exception("column must be supplied") unless $column;
46
d8dbe471 47 my $orig_attrs = $rs->_resolved_attrs;
48 my $new_parent_rs = $rs->search_rs;
7ae9706c 49
50 # prefetch causes additional columns to be fetched, but we can not just make a new
51 # rs via the _resolved_attrs trick - we need to retain the separation between
bed3a173 52 # +select/+as and select/as. At the same time we want to preserve any joins that the
53 # prefetch would otherwise generate.
d8dbe471 54
55 my $new_attrs = $new_parent_rs->{attrs} ||= {};
56 $new_attrs->{join} = $rs->_merge_attr( delete $new_attrs->{join}, delete $new_attrs->{prefetch} );
b6e85b48 57
152002c4 58 # If $column can be found in the 'as' list of the parent resultset, use the
59 # corresponding element of its 'select' list (to keep any custom column
60 # definition set up with 'select' or '+select' attrs), otherwise use $column
61 # (to create a new column definition on-the-fly).
7ae9706c 62
d8dbe471 63 my $as_list = $orig_attrs->{as} || [];
64 my $select_list = $orig_attrs->{select} || [];
b6e85b48 65 my $as_index = List::Util::first { ($as_list->[$_] || "") eq $column } 0..$#$as_list;
b6e85b48 66 my $select = defined $as_index ? $select_list->[$as_index] : $column;
67
d8dbe471 68 # {collapse} would mean a has_many join was injected, which in turn means
722c0140 69 # we need to group *IF WE CAN* (only if the column in question is unique)
d8dbe471 70 if (!$new_attrs->{group_by} && keys %{$orig_attrs->{collapse}}) {
71
72 # scan for a constraint that would contain our column only - that'd be proof
73 # enough it is unique
74 my $constraints = { $rs->result_source->unique_constraints };
75 for my $constraint_columns ( values %$constraints ) {
76
77 next unless @$constraint_columns == 1;
78
79 my $col = $constraint_columns->[0];
80 my $fqcol = join ('.', $new_attrs->{alias}, $col);
81
82 if ($col eq $select or $fqcol eq $select) {
83 $new_attrs->{group_by} = [ $select ];
722c0140 84 delete $new_attrs->{distinct}; # it is ignored when group_by is present
d8dbe471 85 last;
86 }
87 }
722c0140 88
89 if (!$new_attrs->{group_by}) {
90 carp (
91 "Attempting to retrieve non-unique column '$column' on a resultset containing "
92 . 'one-to-many joins will return duplicate results.'
93 );
94 }
d8dbe471 95 }
96
b6e85b48 97 my $new = bless { _select => $select, _as => $column, _parent_resultset => $new_parent_rs }, $class;
2bb7b40b 98 return $new;
99}
100
70bb942d 101=head2 as_query (EXPERIMENTAL)
658fa250 102
103=over 4
104
428a645e 105=item Arguments: none
658fa250 106
4dc99a01 107=item Return Value: \[ $sql, @bind ]
658fa250 108
109=back
110
111Returns the SQL query and bind vars associated with the invocant.
112
03834f77 113This is generally used as the RHS for a subquery.
c7a9d102 114
6a9530d1 115B<NOTE>: This feature is still experimental.
116
c7a9d102 117=cut
118
0f6fc705 119sub as_query { return shift->_resultset->as_query(@_) }
c7a9d102 120
2bb7b40b 121=head2 next
122
123=over 4
124
125=item Arguments: none
126
127=item Return Value: $value
128
129=back
130
eb98561c 131Returns the next value of the column in the resultset (or C<undef> if
132there is none).
2bb7b40b 133
eb98561c 134Much like L<DBIx::Class::ResultSet/next> but just returning the
135one value.
2bb7b40b 136
137=cut
138
139sub next {
140 my $self = shift;
b7c79955 141
142 # using cursor so we don't inflate anything
66521001 143 my ($row) = $self->_resultset->cursor->next;
b7c79955 144
2bb7b40b 145 return $row;
146}
147
148=head2 all
149
150=over 4
151
152=item Arguments: none
153
154=item Return Value: @values
155
156=back
157
eb98561c 158Returns all values of the column in the resultset (or C<undef> if
159there are none).
2bb7b40b 160
eb98561c 161Much like L<DBIx::Class::ResultSet/all> but returns values rather
162than row objects.
2bb7b40b 163
164=cut
165
166sub all {
167 my $self = shift;
b7c79955 168
169 # using cursor so we don't inflate anything
66521001 170 return map { $_->[0] } $self->_resultset->cursor->all;
171}
172
173=head2 reset
174
175=over 4
176
177=item Arguments: none
178
179=item Return Value: $self
180
181=back
182
183Resets the underlying resultset's cursor, so you can iterate through the
184elements of the column again.
185
186Much like L<DBIx::Class::ResultSet/reset>.
187
188=cut
189
190sub reset {
191 my $self = shift;
192 $self->_resultset->cursor->reset;
b7c79955 193 return $self;
66521001 194}
195
196=head2 first
197
198=over 4
199
200=item Arguments: none
201
202=item Return Value: $value
203
204=back
205
206Resets the underlying resultset and returns the next value of the column in the
207resultset (or C<undef> if there is none).
208
209Much like L<DBIx::Class::ResultSet/first> but just returning the one value.
210
211=cut
212
213sub first {
214 my $self = shift;
b7c79955 215
216 # using cursor so we don't inflate anything
217 $self->_resultset->cursor->reset;
01dc6781 218 my ($row) = $self->_resultset->cursor->next;
b7c79955 219
66521001 220 return $row;
2bb7b40b 221}
222
4e55c3ae 223=head2 single
224
225=over 4
226
227=item Arguments: none
228
229=item Return Value: $value
230
231=back
232
233Much like L<DBIx::Class::ResultSet/single> fetches one and only one column
234value using the cursor directly. If additional rows are present a warning
235is issued before discarding the cursor.
236
237=cut
238
239sub single {
240 my $self = shift;
241
242 my $attrs = $self->_resultset->_resolved_attrs;
243 my ($row) = $self->_resultset->result_source->storage->select_single(
244 $attrs->{from}, $attrs->{select}, $attrs->{where}, $attrs
245 );
246
247 return $row;
248}
249
2bb7b40b 250=head2 min
251
252=over 4
253
254=item Arguments: none
255
256=item Return Value: $lowest_value
257
258=back
259
eb98561c 260 my $first_year = $year_col->min();
261
262Wrapper for ->func. Returns the lowest value of the column in the
263resultset (or C<undef> if there are none).
2bb7b40b 264
265=cut
266
267sub min {
6b051e14 268 return shift->func('MIN');
2bb7b40b 269}
270
4fa7bc22 271=head2 min_rs
272
273=over 4
274
275=item Arguments: none
276
277=item Return Value: $resultset
278
279=back
280
281 my $rs = $year_col->min_rs();
282
283Wrapper for ->func_rs for function MIN().
284
285=cut
286
287sub min_rs { return shift->func_rs('MIN') }
288
2bb7b40b 289=head2 max
290
291=over 4
292
293=item Arguments: none
294
295=item Return Value: $highest_value
296
297=back
298
eb98561c 299 my $last_year = $year_col->max();
300
301Wrapper for ->func. Returns the highest value of the column in the
302resultset (or C<undef> if there are none).
2bb7b40b 303
304=cut
305
306sub max {
6b051e14 307 return shift->func('MAX');
2bb7b40b 308}
309
4fa7bc22 310=head2 max_rs
311
312=over 4
313
314=item Arguments: none
315
316=item Return Value: $resultset
317
318=back
319
320 my $rs = $year_col->max_rs();
321
322Wrapper for ->func_rs for function MAX().
323
324=cut
325
326sub max_rs { return shift->func_rs('MAX') }
327
2bb7b40b 328=head2 sum
329
330=over 4
331
332=item Arguments: none
333
334=item Return Value: $sum_of_values
335
336=back
337
eb98561c 338 my $total = $prices_col->sum();
339
340Wrapper for ->func. Returns the sum of all the values in the column of
341the resultset. Use on varchar-like columns at your own risk.
2bb7b40b 342
343=cut
344
345sub sum {
6b051e14 346 return shift->func('SUM');
2bb7b40b 347}
348
4fa7bc22 349=head2 sum_rs
350
351=over 4
352
353=item Arguments: none
354
355=item Return Value: $resultset
356
357=back
358
359 my $rs = $year_col->sum_rs();
360
361Wrapper for ->func_rs for function SUM().
362
363=cut
364
365sub sum_rs { return shift->func_rs('SUM') }
366
2bb7b40b 367=head2 func
368
369=over 4
370
371=item Arguments: $function
372
373=item Return Value: $function_return_value
374
375=back
376
e8419341 377 $rs = $schema->resultset("CD")->search({});
378 $length = $rs->get_column('title')->func('LENGTH');
2bb7b40b 379
eb98561c 380Runs a query using the function on the column and returns the
381value. Produces the following SQL:
382
383 SELECT LENGTH( title ) FROM cd me
2bb7b40b 384
385=cut
386
387sub func {
6b051e14 388 my ($self,$function) = @_;
4fa7bc22 389 my $cursor = $self->func_rs($function)->cursor;
d4daee7b 390
5d62876f 391 if( wantarray ) {
392 return map { $_->[ 0 ] } $cursor->all;
393 }
394
395 return ( $cursor->next )[ 0 ];
2bb7b40b 396}
397
4fa7bc22 398=head2 func_rs
399
400=over 4
401
402=item Arguments: $function
403
404=item Return Value: $resultset
405
406=back
407
408Creates the resultset that C<func()> uses to run its query.
409
410=cut
411
412sub func_rs {
413 my ($self,$function) = @_;
414 return $self->{_parent_resultset}->search(
415 undef, {
416 select => {$function => $self->{_select}},
417 as => [$self->{_as}],
418 },
419 );
420}
421
5d1fc7dc 422=head2 throw_exception
423
424See L<DBIx::Class::Schema/throw_exception> for details.
d4daee7b 425
5d1fc7dc 426=cut
d4daee7b 427
5d1fc7dc 428sub throw_exception {
429 my $self=shift;
1a58752c 430
5d1fc7dc 431 if (ref $self && $self->{_parent_resultset}) {
1a58752c 432 $self->{_parent_resultset}->throw_exception(@_);
433 }
434 else {
435 DBIx::Class::Exception->throw(@_);
5d1fc7dc 436 }
437}
438
b6e85b48 439# _resultset
440#
441# Arguments: none
442#
443# Return Value: $resultset
444#
445# $year_col->_resultset->next
446#
447# Returns the underlying resultset. Creates it from the parent resultset if
448# necessary.
b7c79955 449#
66521001 450sub _resultset {
451 my $self = shift;
452
453 return $self->{_resultset} ||= $self->{_parent_resultset}->search(undef,
454 {
455 select => [$self->{_select}],
456 as => [$self->{_as}]
457 }
458 );
459}
460
2bb7b40b 4611;
462
463=head1 AUTHORS
464
465Luke Saunders <luke.saunders@gmail.com>
466
eb98561c 467Jess Robinson
468
2bb7b40b 469=head1 LICENSE
470
471You may distribute this code under the same terms as Perl itself.
472
473=cut