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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 | |
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45 | $rs->throw_exception('column must be supplied') unless $column; |
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46 | |
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47 | my $orig_attrs = $rs->_resolved_attrs; |
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48 | |
49 | # If $column can be found in the 'as' list of the parent resultset, use the |
50 | # corresponding element of its 'select' list (to keep any custom column |
51 | # definition set up with 'select' or '+select' attrs), otherwise use $column |
52 | # (to create a new column definition on-the-fly). |
53 | my $as_list = $orig_attrs->{as} || []; |
54 | my $select_list = $orig_attrs->{select} || []; |
55 | my $as_index = List::Util::first { ($as_list->[$_] || "") eq $column } 0..$#$as_list; |
56 | my $select = defined $as_index ? $select_list->[$as_index] : $column; |
57 | |
58 | my $new_parent_rs; |
59 | # analyze the order_by, and see if it is done over a function/nonexistentcolumn |
60 | # if this is the case we will need to wrap a subquery since the result of RSC |
61 | # *must* be a single column select |
62 | my %collist = map { $_ => 1 } ($rs->result_source->columns, $column); |
63 | if ( |
64 | scalar grep |
65 | { ! $collist{$_} } |
66 | ( $rs->result_source->schema->storage->_parse_order_by ($orig_attrs->{order_by} ) ) |
67 | ) { |
68 | my $alias = $rs->current_source_alias; |
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69 | # nuke the prefetch before collapsing to sql |
70 | my $subq_rs = $rs->search; |
71 | $subq_rs->{attrs}{join} = $subq_rs->_merge_attr( $subq_rs->{attrs}{join}, delete $subq_rs->{attrs}{prefetch} ); |
72 | |
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73 | $new_parent_rs = $rs->result_source->resultset->search ( {}, { |
74 | alias => $alias, |
75 | from => [{ |
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76 | $alias => $subq_rs->as_query, |
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77 | -alias => $alias, |
78 | -source_handle => $rs->result_source->handle, |
79 | }] |
80 | }); |
81 | } |
82 | |
83 | $new_parent_rs ||= $rs->search_rs; |
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84 | my $new_attrs = $new_parent_rs->{attrs} ||= {}; |
85 | |
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86 | # prefetch causes additional columns to be fetched, but we can not just make a new |
87 | # rs via the _resolved_attrs trick - we need to retain the separation between |
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88 | # +select/+as and select/as. At the same time we want to preserve any joins that the |
89 | # prefetch would otherwise generate. |
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90 | $new_attrs->{join} = $rs->_merge_attr( $new_attrs->{join}, delete $new_attrs->{prefetch} ); |
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91 | |
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92 | # {collapse} would mean a has_many join was injected, which in turn means |
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93 | # we need to group *IF WE CAN* (only if the column in question is unique) |
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94 | if (!$new_attrs->{group_by} && keys %{$orig_attrs->{collapse}}) { |
95 | |
96 | # scan for a constraint that would contain our column only - that'd be proof |
97 | # enough it is unique |
98 | my $constraints = { $rs->result_source->unique_constraints }; |
99 | for my $constraint_columns ( values %$constraints ) { |
100 | |
101 | next unless @$constraint_columns == 1; |
102 | |
103 | my $col = $constraint_columns->[0]; |
104 | my $fqcol = join ('.', $new_attrs->{alias}, $col); |
105 | |
106 | if ($col eq $select or $fqcol eq $select) { |
107 | $new_attrs->{group_by} = [ $select ]; |
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108 | delete $new_attrs->{distinct}; # it is ignored when group_by is present |
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109 | last; |
110 | } |
111 | } |
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112 | |
113 | if (!$new_attrs->{group_by}) { |
114 | carp ( |
115 | "Attempting to retrieve non-unique column '$column' on a resultset containing " |
116 | . 'one-to-many joins will return duplicate results.' |
117 | ); |
118 | } |
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119 | } |
120 | |
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121 | my $new = bless { _select => $select, _as => $column, _parent_resultset => $new_parent_rs }, $class; |
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122 | return $new; |
123 | } |
124 | |
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125 | =head2 as_query |
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126 | |
127 | =over 4 |
128 | |
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129 | =item Arguments: none |
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130 | |
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131 | =item Return Value: \[ $sql, @bind ] |
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132 | |
133 | =back |
134 | |
135 | Returns the SQL query and bind vars associated with the invocant. |
136 | |
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137 | This is generally used as the RHS for a subquery. |
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138 | |
139 | =cut |
140 | |
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141 | sub as_query { return shift->_resultset->as_query(@_) } |
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142 | |
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143 | =head2 next |
144 | |
145 | =over 4 |
146 | |
147 | =item Arguments: none |
148 | |
149 | =item Return Value: $value |
150 | |
151 | =back |
152 | |
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153 | Returns the next value of the column in the resultset (or C<undef> if |
154 | there is none). |
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155 | |
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156 | Much like L<DBIx::Class::ResultSet/next> but just returning the |
157 | one value. |
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158 | |
159 | =cut |
160 | |
161 | sub next { |
162 | my $self = shift; |
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163 | |
164 | # using cursor so we don't inflate anything |
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165 | my ($row) = $self->_resultset->cursor->next; |
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166 | |
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167 | return $row; |
168 | } |
169 | |
170 | =head2 all |
171 | |
172 | =over 4 |
173 | |
174 | =item Arguments: none |
175 | |
176 | =item Return Value: @values |
177 | |
178 | =back |
179 | |
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180 | Returns all values of the column in the resultset (or C<undef> if |
181 | there are none). |
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182 | |
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183 | Much like L<DBIx::Class::ResultSet/all> but returns values rather |
184 | than row objects. |
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185 | |
186 | =cut |
187 | |
188 | sub all { |
189 | my $self = shift; |
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190 | |
191 | # using cursor so we don't inflate anything |
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192 | return map { $_->[0] } $self->_resultset->cursor->all; |
193 | } |
194 | |
195 | =head2 reset |
196 | |
197 | =over 4 |
198 | |
199 | =item Arguments: none |
200 | |
201 | =item Return Value: $self |
202 | |
203 | =back |
204 | |
205 | Resets the underlying resultset's cursor, so you can iterate through the |
206 | elements of the column again. |
207 | |
208 | Much like L<DBIx::Class::ResultSet/reset>. |
209 | |
210 | =cut |
211 | |
212 | sub reset { |
213 | my $self = shift; |
214 | $self->_resultset->cursor->reset; |
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215 | return $self; |
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216 | } |
217 | |
218 | =head2 first |
219 | |
220 | =over 4 |
221 | |
222 | =item Arguments: none |
223 | |
224 | =item Return Value: $value |
225 | |
226 | =back |
227 | |
228 | Resets the underlying resultset and returns the next value of the column in the |
229 | resultset (or C<undef> if there is none). |
230 | |
231 | Much like L<DBIx::Class::ResultSet/first> but just returning the one value. |
232 | |
233 | =cut |
234 | |
235 | sub first { |
236 | my $self = shift; |
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237 | |
238 | # using cursor so we don't inflate anything |
239 | $self->_resultset->cursor->reset; |
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240 | my ($row) = $self->_resultset->cursor->next; |
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241 | |
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242 | return $row; |
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243 | } |
244 | |
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245 | =head2 single |
246 | |
247 | =over 4 |
248 | |
249 | =item Arguments: none |
250 | |
251 | =item Return Value: $value |
252 | |
253 | =back |
254 | |
255 | Much like L<DBIx::Class::ResultSet/single> fetches one and only one column |
256 | value using the cursor directly. If additional rows are present a warning |
257 | is issued before discarding the cursor. |
258 | |
259 | =cut |
260 | |
261 | sub single { |
262 | my $self = shift; |
263 | |
264 | my $attrs = $self->_resultset->_resolved_attrs; |
265 | my ($row) = $self->_resultset->result_source->storage->select_single( |
266 | $attrs->{from}, $attrs->{select}, $attrs->{where}, $attrs |
267 | ); |
268 | |
269 | return $row; |
270 | } |
271 | |
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272 | =head2 min |
273 | |
274 | =over 4 |
275 | |
276 | =item Arguments: none |
277 | |
278 | =item Return Value: $lowest_value |
279 | |
280 | =back |
281 | |
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282 | my $first_year = $year_col->min(); |
283 | |
284 | Wrapper for ->func. Returns the lowest value of the column in the |
285 | resultset (or C<undef> if there are none). |
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286 | |
287 | =cut |
288 | |
289 | sub min { |
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290 | return shift->func('MIN'); |
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291 | } |
292 | |
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293 | =head2 min_rs |
294 | |
295 | =over 4 |
296 | |
297 | =item Arguments: none |
298 | |
299 | =item Return Value: $resultset |
300 | |
301 | =back |
302 | |
303 | my $rs = $year_col->min_rs(); |
304 | |
305 | Wrapper for ->func_rs for function MIN(). |
306 | |
307 | =cut |
308 | |
309 | sub min_rs { return shift->func_rs('MIN') } |
310 | |
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311 | =head2 max |
312 | |
313 | =over 4 |
314 | |
315 | =item Arguments: none |
316 | |
317 | =item Return Value: $highest_value |
318 | |
319 | =back |
320 | |
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321 | my $last_year = $year_col->max(); |
322 | |
323 | Wrapper for ->func. Returns the highest value of the column in the |
324 | resultset (or C<undef> if there are none). |
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325 | |
326 | =cut |
327 | |
328 | sub max { |
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329 | return shift->func('MAX'); |
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330 | } |
331 | |
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332 | =head2 max_rs |
333 | |
334 | =over 4 |
335 | |
336 | =item Arguments: none |
337 | |
338 | =item Return Value: $resultset |
339 | |
340 | =back |
341 | |
342 | my $rs = $year_col->max_rs(); |
343 | |
344 | Wrapper for ->func_rs for function MAX(). |
345 | |
346 | =cut |
347 | |
348 | sub max_rs { return shift->func_rs('MAX') } |
349 | |
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350 | =head2 sum |
351 | |
352 | =over 4 |
353 | |
354 | =item Arguments: none |
355 | |
356 | =item Return Value: $sum_of_values |
357 | |
358 | =back |
359 | |
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360 | my $total = $prices_col->sum(); |
361 | |
362 | Wrapper for ->func. Returns the sum of all the values in the column of |
363 | the resultset. Use on varchar-like columns at your own risk. |
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364 | |
365 | =cut |
366 | |
367 | sub sum { |
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368 | return shift->func('SUM'); |
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369 | } |
370 | |
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371 | =head2 sum_rs |
372 | |
373 | =over 4 |
374 | |
375 | =item Arguments: none |
376 | |
377 | =item Return Value: $resultset |
378 | |
379 | =back |
380 | |
381 | my $rs = $year_col->sum_rs(); |
382 | |
383 | Wrapper for ->func_rs for function SUM(). |
384 | |
385 | =cut |
386 | |
387 | sub sum_rs { return shift->func_rs('SUM') } |
388 | |
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389 | =head2 func |
390 | |
391 | =over 4 |
392 | |
393 | =item Arguments: $function |
394 | |
395 | =item Return Value: $function_return_value |
396 | |
397 | =back |
398 | |
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399 | $rs = $schema->resultset("CD")->search({}); |
400 | $length = $rs->get_column('title')->func('LENGTH'); |
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401 | |
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402 | Runs a query using the function on the column and returns the |
403 | value. Produces the following SQL: |
404 | |
405 | SELECT LENGTH( title ) FROM cd me |
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406 | |
407 | =cut |
408 | |
409 | sub func { |
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410 | my ($self,$function) = @_; |
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411 | my $cursor = $self->func_rs($function)->cursor; |
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412 | |
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413 | if( wantarray ) { |
414 | return map { $_->[ 0 ] } $cursor->all; |
415 | } |
416 | |
417 | return ( $cursor->next )[ 0 ]; |
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418 | } |
419 | |
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420 | =head2 func_rs |
421 | |
422 | =over 4 |
423 | |
424 | =item Arguments: $function |
425 | |
426 | =item Return Value: $resultset |
427 | |
428 | =back |
429 | |
430 | Creates the resultset that C<func()> uses to run its query. |
431 | |
432 | =cut |
433 | |
434 | sub func_rs { |
435 | my ($self,$function) = @_; |
436 | return $self->{_parent_resultset}->search( |
437 | undef, { |
438 | select => {$function => $self->{_select}}, |
439 | as => [$self->{_as}], |
440 | }, |
441 | ); |
442 | } |
443 | |
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444 | =head2 throw_exception |
445 | |
446 | See L<DBIx::Class::Schema/throw_exception> for details. |
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447 | |
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448 | =cut |
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449 | |
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450 | sub throw_exception { |
451 | my $self=shift; |
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452 | |
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453 | if (ref $self && $self->{_parent_resultset}) { |
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454 | $self->{_parent_resultset}->throw_exception(@_); |
455 | } |
456 | else { |
457 | DBIx::Class::Exception->throw(@_); |
5d1fc7dc |
458 | } |
459 | } |
460 | |
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461 | # _resultset |
462 | # |
463 | # Arguments: none |
464 | # |
465 | # Return Value: $resultset |
466 | # |
467 | # $year_col->_resultset->next |
468 | # |
469 | # Returns the underlying resultset. Creates it from the parent resultset if |
470 | # necessary. |
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471 | # |
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472 | sub _resultset { |
473 | my $self = shift; |
474 | |
475 | return $self->{_resultset} ||= $self->{_parent_resultset}->search(undef, |
476 | { |
477 | select => [$self->{_select}], |
478 | as => [$self->{_as}] |
479 | } |
480 | ); |
481 | } |
482 | |
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483 | 1; |
484 | |
485 | =head1 AUTHORS |
486 | |
487 | Luke Saunders <luke.saunders@gmail.com> |
488 | |
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489 | Jess Robinson |
490 | |
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491 | =head1 LICENSE |
492 | |
493 | You may distribute this code under the same terms as Perl itself. |
494 | |
495 | =cut |