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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 | use DBIx::Class::Carp; |
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8 | use DBIx::Class::Exception; |
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9 | |
10 | # not importing first() as it will clash with our own method |
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11 | use List::Util (); |
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12 | |
13 | =head1 NAME |
14 | |
15 | DBIx::Class::ResultSetColumn - helpful methods for messing |
16 | with a single column of the resultset |
17 | |
18 | =head1 SYNOPSIS |
19 | |
20 | $rs = $schema->resultset('CD')->search({ artist => 'Tool' }); |
21 | $rs_column = $rs->get_column('year'); |
22 | $max_year = $rs_column->max; #returns latest year |
23 | |
24 | =head1 DESCRIPTION |
25 | |
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26 | A convenience class used to perform operations on a specific column of |
27 | a resultset. |
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28 | |
29 | =cut |
30 | |
31 | =head1 METHODS |
32 | |
33 | =head2 new |
34 | |
35 | my $obj = DBIx::Class::ResultSetColumn->new($rs, $column); |
36 | |
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37 | Creates a new resultset column object from the resultset and column |
38 | passed as params. Used internally by L<DBIx::Class::ResultSet/get_column>. |
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39 | |
40 | =cut |
41 | |
42 | sub new { |
43 | my ($class, $rs, $column) = @_; |
44 | $class = ref $class if ref $class; |
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45 | |
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46 | $rs->throw_exception('column must be supplied') unless $column; |
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47 | |
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48 | my $orig_attrs = $rs->_resolved_attrs; |
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49 | my $alias = $rs->current_source_alias; |
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50 | |
51 | # If $column can be found in the 'as' list of the parent resultset, use the |
52 | # corresponding element of its 'select' list (to keep any custom column |
53 | # definition set up with 'select' or '+select' attrs), otherwise use $column |
54 | # (to create a new column definition on-the-fly). |
55 | my $as_list = $orig_attrs->{as} || []; |
56 | my $select_list = $orig_attrs->{select} || []; |
57 | my $as_index = List::Util::first { ($as_list->[$_] || "") eq $column } 0..$#$as_list; |
58 | my $select = defined $as_index ? $select_list->[$as_index] : $column; |
59 | |
60 | my $new_parent_rs; |
61 | # analyze the order_by, and see if it is done over a function/nonexistentcolumn |
62 | # if this is the case we will need to wrap a subquery since the result of RSC |
63 | # *must* be a single column select |
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64 | my %collist = map |
65 | { $_ => 1, ($_ =~ /\./) ? () : ( "$alias.$_" => 1 ) } |
66 | ($rs->result_source->columns, $column) |
67 | ; |
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68 | if ( |
69 | scalar grep |
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70 | { ! $collist{$_->[0]} } |
71 | ( $rs->result_source->schema->storage->_extract_order_criteria ($orig_attrs->{order_by} ) ) |
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72 | ) { |
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73 | # nuke the prefetch before collapsing to sql |
74 | my $subq_rs = $rs->search; |
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75 | $subq_rs->{attrs}{join} = $subq_rs->_merge_joinpref_attr( $subq_rs->{attrs}{join}, delete $subq_rs->{attrs}{prefetch} ); |
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76 | $new_parent_rs = $subq_rs->as_subselect_rs; |
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77 | } |
78 | |
79 | $new_parent_rs ||= $rs->search_rs; |
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80 | my $new_attrs = $new_parent_rs->{attrs} ||= {}; |
81 | |
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82 | # prefetch causes additional columns to be fetched, but we can not just make a new |
83 | # rs via the _resolved_attrs trick - we need to retain the separation between |
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84 | # +select/+as and select/as. At the same time we want to preserve any joins that the |
85 | # prefetch would otherwise generate. |
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86 | $new_attrs->{join} = $rs->_merge_joinpref_attr( $new_attrs->{join}, delete $new_attrs->{prefetch} ); |
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87 | |
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88 | # {collapse} would mean a has_many join was injected, which in turn means |
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89 | # we need to group *IF WE CAN* (only if the column in question is unique) |
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90 | if (!$orig_attrs->{group_by} && keys %{$orig_attrs->{collapse}}) { |
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91 | |
92 | # scan for a constraint that would contain our column only - that'd be proof |
93 | # enough it is unique |
94 | my $constraints = { $rs->result_source->unique_constraints }; |
95 | for my $constraint_columns ( values %$constraints ) { |
96 | |
97 | next unless @$constraint_columns == 1; |
98 | |
99 | my $col = $constraint_columns->[0]; |
100 | my $fqcol = join ('.', $new_attrs->{alias}, $col); |
101 | |
102 | if ($col eq $select or $fqcol eq $select) { |
103 | $new_attrs->{group_by} = [ $select ]; |
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104 | delete $new_attrs->{distinct}; # it is ignored when group_by is present |
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105 | last; |
106 | } |
107 | } |
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108 | |
109 | if (!$new_attrs->{group_by}) { |
110 | carp ( |
111 | "Attempting to retrieve non-unique column '$column' on a resultset containing " |
112 | . 'one-to-many joins will return duplicate results.' |
113 | ); |
114 | } |
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115 | } |
116 | |
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117 | my $new = bless { _select => $select, _as => $column, _parent_resultset => $new_parent_rs }, $class; |
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118 | return $new; |
119 | } |
120 | |
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121 | =head2 as_query |
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122 | |
123 | =over 4 |
124 | |
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125 | =item Arguments: none |
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126 | |
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127 | =item Return Value: \[ $sql, @bind ] |
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128 | |
129 | =back |
130 | |
131 | Returns the SQL query and bind vars associated with the invocant. |
132 | |
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133 | This is generally used as the RHS for a subquery. |
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134 | |
135 | =cut |
136 | |
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137 | sub as_query { return shift->_resultset->as_query(@_) } |
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138 | |
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139 | =head2 next |
140 | |
141 | =over 4 |
142 | |
143 | =item Arguments: none |
144 | |
145 | =item Return Value: $value |
146 | |
147 | =back |
148 | |
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149 | Returns the next value of the column in the resultset (or C<undef> if |
150 | there is none). |
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151 | |
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152 | Much like L<DBIx::Class::ResultSet/next> but just returning the |
153 | one value. |
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154 | |
155 | =cut |
156 | |
157 | sub next { |
158 | my $self = shift; |
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159 | |
160 | # using cursor so we don't inflate anything |
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161 | my ($row) = $self->_resultset->cursor->next; |
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162 | |
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163 | return $row; |
164 | } |
165 | |
166 | =head2 all |
167 | |
168 | =over 4 |
169 | |
170 | =item Arguments: none |
171 | |
172 | =item Return Value: @values |
173 | |
174 | =back |
175 | |
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176 | Returns all values of the column in the resultset (or C<undef> if |
177 | there are none). |
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178 | |
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179 | Much like L<DBIx::Class::ResultSet/all> but returns values rather |
180 | than row objects. |
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181 | |
182 | =cut |
183 | |
184 | sub all { |
185 | my $self = shift; |
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186 | |
187 | # using cursor so we don't inflate anything |
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188 | return map { $_->[0] } $self->_resultset->cursor->all; |
189 | } |
190 | |
191 | =head2 reset |
192 | |
193 | =over 4 |
194 | |
195 | =item Arguments: none |
196 | |
197 | =item Return Value: $self |
198 | |
199 | =back |
200 | |
201 | Resets the underlying resultset's cursor, so you can iterate through the |
202 | elements of the column again. |
203 | |
204 | Much like L<DBIx::Class::ResultSet/reset>. |
205 | |
206 | =cut |
207 | |
208 | sub reset { |
209 | my $self = shift; |
210 | $self->_resultset->cursor->reset; |
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211 | return $self; |
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212 | } |
213 | |
214 | =head2 first |
215 | |
216 | =over 4 |
217 | |
218 | =item Arguments: none |
219 | |
220 | =item Return Value: $value |
221 | |
222 | =back |
223 | |
224 | Resets the underlying resultset and returns the next value of the column in the |
225 | resultset (or C<undef> if there is none). |
226 | |
227 | Much like L<DBIx::Class::ResultSet/first> but just returning the one value. |
228 | |
229 | =cut |
230 | |
231 | sub first { |
232 | my $self = shift; |
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233 | |
234 | # using cursor so we don't inflate anything |
235 | $self->_resultset->cursor->reset; |
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236 | my ($row) = $self->_resultset->cursor->next; |
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237 | |
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238 | return $row; |
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239 | } |
240 | |
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241 | =head2 single |
242 | |
243 | =over 4 |
244 | |
245 | =item Arguments: none |
246 | |
247 | =item Return Value: $value |
248 | |
249 | =back |
250 | |
251 | Much like L<DBIx::Class::ResultSet/single> fetches one and only one column |
252 | value using the cursor directly. If additional rows are present a warning |
253 | is issued before discarding the cursor. |
254 | |
255 | =cut |
256 | |
257 | sub single { |
258 | my $self = shift; |
259 | |
260 | my $attrs = $self->_resultset->_resolved_attrs; |
261 | my ($row) = $self->_resultset->result_source->storage->select_single( |
262 | $attrs->{from}, $attrs->{select}, $attrs->{where}, $attrs |
263 | ); |
264 | |
265 | return $row; |
266 | } |
267 | |
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268 | =head2 min |
269 | |
270 | =over 4 |
271 | |
272 | =item Arguments: none |
273 | |
274 | =item Return Value: $lowest_value |
275 | |
276 | =back |
277 | |
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278 | my $first_year = $year_col->min(); |
279 | |
280 | Wrapper for ->func. Returns the lowest value of the column in the |
281 | resultset (or C<undef> if there are none). |
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282 | |
283 | =cut |
284 | |
285 | sub min { |
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286 | return shift->func('MIN'); |
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287 | } |
288 | |
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289 | =head2 min_rs |
290 | |
291 | =over 4 |
292 | |
293 | =item Arguments: none |
294 | |
295 | =item Return Value: $resultset |
296 | |
297 | =back |
298 | |
299 | my $rs = $year_col->min_rs(); |
300 | |
301 | Wrapper for ->func_rs for function MIN(). |
302 | |
303 | =cut |
304 | |
305 | sub min_rs { return shift->func_rs('MIN') } |
306 | |
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307 | =head2 max |
308 | |
309 | =over 4 |
310 | |
311 | =item Arguments: none |
312 | |
313 | =item Return Value: $highest_value |
314 | |
315 | =back |
316 | |
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317 | my $last_year = $year_col->max(); |
318 | |
319 | Wrapper for ->func. Returns the highest value of the column in the |
320 | resultset (or C<undef> if there are none). |
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321 | |
322 | =cut |
323 | |
324 | sub max { |
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325 | return shift->func('MAX'); |
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326 | } |
327 | |
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328 | =head2 max_rs |
329 | |
330 | =over 4 |
331 | |
332 | =item Arguments: none |
333 | |
334 | =item Return Value: $resultset |
335 | |
336 | =back |
337 | |
338 | my $rs = $year_col->max_rs(); |
339 | |
340 | Wrapper for ->func_rs for function MAX(). |
341 | |
342 | =cut |
343 | |
344 | sub max_rs { return shift->func_rs('MAX') } |
345 | |
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346 | =head2 sum |
347 | |
348 | =over 4 |
349 | |
350 | =item Arguments: none |
351 | |
352 | =item Return Value: $sum_of_values |
353 | |
354 | =back |
355 | |
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356 | my $total = $prices_col->sum(); |
357 | |
358 | Wrapper for ->func. Returns the sum of all the values in the column of |
359 | the resultset. Use on varchar-like columns at your own risk. |
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360 | |
361 | =cut |
362 | |
363 | sub sum { |
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364 | return shift->func('SUM'); |
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365 | } |
366 | |
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367 | =head2 sum_rs |
368 | |
369 | =over 4 |
370 | |
371 | =item Arguments: none |
372 | |
373 | =item Return Value: $resultset |
374 | |
375 | =back |
376 | |
377 | my $rs = $year_col->sum_rs(); |
378 | |
379 | Wrapper for ->func_rs for function SUM(). |
380 | |
381 | =cut |
382 | |
383 | sub sum_rs { return shift->func_rs('SUM') } |
384 | |
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385 | =head2 func |
386 | |
387 | =over 4 |
388 | |
389 | =item Arguments: $function |
390 | |
391 | =item Return Value: $function_return_value |
392 | |
393 | =back |
394 | |
e8419341 |
395 | $rs = $schema->resultset("CD")->search({}); |
396 | $length = $rs->get_column('title')->func('LENGTH'); |
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397 | |
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398 | Runs a query using the function on the column and returns the |
399 | value. Produces the following SQL: |
400 | |
401 | SELECT LENGTH( title ) FROM cd me |
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402 | |
403 | =cut |
404 | |
405 | sub func { |
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406 | my ($self,$function) = @_; |
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407 | my $cursor = $self->func_rs($function)->cursor; |
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408 | |
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409 | if( wantarray ) { |
410 | return map { $_->[ 0 ] } $cursor->all; |
411 | } |
412 | |
413 | return ( $cursor->next )[ 0 ]; |
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414 | } |
415 | |
4fa7bc22 |
416 | =head2 func_rs |
417 | |
418 | =over 4 |
419 | |
420 | =item Arguments: $function |
421 | |
422 | =item Return Value: $resultset |
423 | |
424 | =back |
425 | |
426 | Creates the resultset that C<func()> uses to run its query. |
427 | |
428 | =cut |
429 | |
430 | sub func_rs { |
431 | my ($self,$function) = @_; |
432 | return $self->{_parent_resultset}->search( |
433 | undef, { |
434 | select => {$function => $self->{_select}}, |
435 | as => [$self->{_as}], |
436 | }, |
437 | ); |
438 | } |
439 | |
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440 | =head2 throw_exception |
441 | |
442 | See L<DBIx::Class::Schema/throw_exception> for details. |
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443 | |
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444 | =cut |
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445 | |
5d1fc7dc |
446 | sub throw_exception { |
447 | my $self=shift; |
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448 | |
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449 | if (ref $self && $self->{_parent_resultset}) { |
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450 | $self->{_parent_resultset}->throw_exception(@_); |
451 | } |
452 | else { |
453 | DBIx::Class::Exception->throw(@_); |
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454 | } |
455 | } |
456 | |
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457 | # _resultset |
458 | # |
459 | # Arguments: none |
460 | # |
461 | # Return Value: $resultset |
462 | # |
463 | # $year_col->_resultset->next |
464 | # |
465 | # Returns the underlying resultset. Creates it from the parent resultset if |
466 | # necessary. |
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467 | # |
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468 | sub _resultset { |
469 | my $self = shift; |
470 | |
471 | return $self->{_resultset} ||= $self->{_parent_resultset}->search(undef, |
472 | { |
473 | select => [$self->{_select}], |
474 | as => [$self->{_as}] |
475 | } |
476 | ); |
477 | } |
478 | |
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479 | 1; |
480 | |
481 | =head1 AUTHORS |
482 | |
483 | Luke Saunders <luke.saunders@gmail.com> |
484 | |
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485 | Jess Robinson |
486 | |
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487 | =head1 LICENSE |
488 | |
489 | You may distribute this code under the same terms as Perl itself. |
490 | |
491 | =cut |