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