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