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1 | =head1 NAME |
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2 | |
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3 | DBIx::Class::Manual::Cookbook - Miscellaneous recipes |
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4 | |
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5 | =head1 SEARCHING |
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6 | |
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7 | =head2 Paged results |
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8 | |
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9 | When you expect a large number of results, you can ask L<DBIx::Class> for a |
264f1571 |
10 | paged resultset, which will fetch only a defined number of records at a time: |
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11 | |
bade79c4 |
12 | my $rs = $schema->resultset('Artist')->search( |
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13 | undef, |
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14 | { |
15 | page => 1, # page to return (defaults to 1) |
16 | rows => 10, # number of results per page |
17 | }, |
18 | ); |
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19 | |
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20 | return $rs->all(); # all records for page 1 |
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21 | |
bade79c4 |
22 | The C<page> attribute does not have to be specified in your search: |
23 | |
24 | my $rs = $schema->resultset('Artist')->search( |
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25 | undef, |
bade79c4 |
26 | { |
27 | rows => 10, |
28 | } |
29 | ); |
faf62551 |
30 | |
bade79c4 |
31 | return $rs->page(1); # DBIx::Class::ResultSet containing first 10 records |
faf62551 |
32 | |
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33 | In either of the above cases, you can get a L<Data::Page> object for the |
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34 | resultset (suitable for use in e.g. a template) using the C<pager> method: |
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35 | |
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36 | return $rs->pager(); |
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37 | |
d2f3e87b |
38 | =head2 Complex WHERE clauses |
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39 | |
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40 | Sometimes you need to formulate a query using specific operators: |
41 | |
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42 | my @albums = $schema->resultset('Album')->search({ |
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43 | artist => { 'like', '%Lamb%' }, |
44 | title => { 'like', '%Fear of Fours%' }, |
45 | }); |
40dbc108 |
46 | |
47 | This results in something like the following C<WHERE> clause: |
48 | |
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49 | WHERE artist LIKE '%Lamb%' AND title LIKE '%Fear of Fours%' |
40dbc108 |
50 | |
51 | Other queries might require slightly more complex logic: |
52 | |
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53 | my @albums = $schema->resultset('Album')->search({ |
35d4fe78 |
54 | -or => [ |
55 | -and => [ |
56 | artist => { 'like', '%Smashing Pumpkins%' }, |
57 | title => 'Siamese Dream', |
58 | ], |
59 | artist => 'Starchildren', |
60 | ], |
61 | }); |
40dbc108 |
62 | |
63 | This results in the following C<WHERE> clause: |
64 | |
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65 | WHERE ( artist LIKE '%Smashing Pumpkins%' AND title = 'Siamese Dream' ) |
66 | OR artist = 'Starchildren' |
40dbc108 |
67 | |
68 | For more information on generating complex queries, see |
69 | L<SQL::Abstract/WHERE CLAUSES>. |
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70 | |
b9823354 |
71 | =head2 Retrieve one and only one row from a resultset |
72 | |
73 | Sometimes you need only the first "top" row of a resultset. While this can be |
74 | easily done with L<< $rs->first|DBIx::Class::ResultSet/first >>, it is suboptimal, |
75 | as a full blown cursor for the resultset will be created and then immediately |
76 | destroyed after fetching the first row object. |
77 | L<< $rs->single|DBIx::Class::ResultSet/single >> is |
78 | designed specifically for this case - it will grab the first returned result |
79 | without even instantiating a cursor. |
80 | |
81 | Before replacing all your calls to C<first()> with C<single()> please observe the |
82 | following CAVEATS: |
83 | |
84 | =over |
85 | |
86 | =item * |
87 | While single() takes a search condition just like search() does, it does |
88 | _not_ accept search attributes. However one can always chain a single() to |
89 | a search(): |
90 | |
91 | my $top_cd = $cd_rs -> search({}, { order_by => 'rating' }) -> single; |
92 | |
93 | |
94 | =item * |
95 | Since single() is the engine behind find(), it is designed to fetch a |
96 | single row per database query. Thus a warning will be issued when the |
97 | underlying SELECT returns more than one row. Sometimes however this usage |
98 | is valid: i.e. we have an arbitrary number of cd's but only one of them is |
99 | at the top of the charts at any given time. If you know what you are doing, |
100 | you can silence the warning by explicitly limiting the resultset size: |
101 | |
102 | my $top_cd = $cd_rs -> search ({}, { order_by => 'rating', rows => 1 }) -> single; |
103 | |
104 | =back |
105 | |
d2f3e87b |
106 | =head2 Arbitrary SQL through a custom ResultSource |
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107 | |
108 | Sometimes you have to run arbitrary SQL because your query is too complex |
109 | (e.g. it contains Unions, Sub-Selects, Stored Procedures, etc.) or has to |
110 | be optimized for your database in a special way, but you still want to |
111 | get the results as a L<DBIx::Class::ResultSet>. |
112 | The recommended way to accomplish this is by defining a separate ResultSource |
113 | for your query. You can then inject complete SQL statements using a scalar |
114 | reference (this is a feature of L<SQL::Abstract>). |
115 | |
116 | Say you want to run a complex custom query on your user data, here's what |
117 | you have to add to your User class: |
118 | |
119 | package My::Schema::User; |
120 | |
121 | use base qw/DBIx::Class/; |
122 | |
123 | # ->load_components, ->table, ->add_columns, etc. |
124 | |
125 | # Make a new ResultSource based on the User class |
126 | my $source = __PACKAGE__->result_source_instance(); |
127 | my $new_source = $source->new( $source ); |
128 | $new_source->source_name( 'UserFriendsComplex' ); |
129 | |
130 | # Hand in your query as a scalar reference |
131 | # It will be added as a sub-select after FROM, |
132 | # so pay attention to the surrounding brackets! |
133 | $new_source->name( \<<SQL ); |
134 | ( SELECT u.* FROM user u |
135 | INNER JOIN user_friends f ON u.id = f.user_id |
136 | WHERE f.friend_user_id = ? |
137 | UNION |
138 | SELECT u.* FROM user u |
139 | INNER JOIN user_friends f ON u.id = f.friend_user_id |
140 | WHERE f.user_id = ? ) |
141 | SQL |
142 | |
143 | # Finally, register your new ResultSource with your Schema |
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144 | My::Schema->register_extra_source( 'UserFriendsComplex' => $new_source ); |
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145 | |
146 | Next, you can execute your complex query using bind parameters like this: |
147 | |
148 | my $friends = [ $schema->resultset( 'UserFriendsComplex' )->search( {}, |
149 | { |
150 | bind => [ 12345, 12345 ] |
151 | } |
152 | ) ]; |
153 | |
d00a5c68 |
154 | ... and you'll get back a perfect L<DBIx::Class::ResultSet> (except, of course, |
155 | that you cannot modify the rows it contains, ie. cannot call L</update>, |
156 | L</delete>, ... on it). |
157 | |
158 | If you prefer to have the definitions of these custom ResultSources in separate |
159 | files (instead of stuffing all of them into the same resultset class), you can |
160 | achieve the same with subclassing the resultset class and defining the |
161 | ResultSource there: |
162 | |
163 | package My::Schema::UserFriendsComplex; |
164 | |
165 | use My::Schema::User; |
166 | use base qw/My::Schema::User/; |
167 | |
168 | __PACKAGE__->table('dummy'); # currently must be called before anything else |
169 | |
170 | # Hand in your query as a scalar reference |
171 | # It will be added as a sub-select after FROM, |
172 | # so pay attention to the surrounding brackets! |
173 | __PACKAGE__->name( \<<SQL ); |
174 | ( SELECT u.* FROM user u |
175 | INNER JOIN user_friends f ON u.id = f.user_id |
176 | WHERE f.friend_user_id = ? |
177 | UNION |
178 | SELECT u.* FROM user u |
179 | INNER JOIN user_friends f ON u.id = f.friend_user_id |
180 | WHERE f.user_id = ? ) |
181 | SQL |
182 | |
183 | TIMTOWDI. |
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184 | |
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185 | =head2 Using specific columns |
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186 | |
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187 | When you only want specific columns from a table, you can use |
188 | C<columns> to specify which ones you need. This is useful to avoid |
189 | loading columns with large amounts of data that you aren't about to |
190 | use anyway: |
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191 | |
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192 | my $rs = $schema->resultset('Artist')->search( |
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193 | undef, |
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194 | { |
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195 | columns => [qw/ name /] |
bade79c4 |
196 | } |
197 | ); |
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198 | |
bade79c4 |
199 | # Equivalent SQL: |
200 | # SELECT artist.name FROM artist |
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201 | |
324572ca |
202 | This is a shortcut for C<select> and C<as>, see below. C<columns> |
203 | cannot be used together with C<select> and C<as>. |
204 | |
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205 | =head2 Using database functions or stored procedures |
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206 | |
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207 | The combination of C<select> and C<as> can be used to return the result of a |
208 | database function or stored procedure as a column value. You use C<select> to |
209 | specify the source for your column value (e.g. a column name, function, or |
210 | stored procedure name). You then use C<as> to set the column name you will use |
211 | to access the returned value: |
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212 | |
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213 | my $rs = $schema->resultset('Artist')->search( |
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214 | {}, |
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215 | { |
216 | select => [ 'name', { LENGTH => 'name' } ], |
217 | as => [qw/ name name_length /], |
218 | } |
219 | ); |
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220 | |
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221 | # Equivalent SQL: |
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222 | # SELECT name name, LENGTH( name ) |
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223 | # FROM artist |
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224 | |
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225 | Note that the C< as > attribute has absolutely nothing to with the sql |
226 | syntax C< SELECT foo AS bar > (see the documentation in |
227 | L<DBIx::Class::ResultSet/ATTRIBUTES>). If your alias exists as a |
228 | column in your base class (i.e. it was added with C<add_columns>), you |
229 | just access it as normal. Our C<Artist> class has a C<name> column, so |
230 | we just use the C<name> accessor: |
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231 | |
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232 | my $artist = $rs->first(); |
233 | my $name = $artist->name(); |
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234 | |
235 | If on the other hand the alias does not correspond to an existing column, you |
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236 | have to fetch the value using the C<get_column> accessor: |
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237 | |
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238 | my $name_length = $artist->get_column('name_length'); |
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239 | |
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240 | If you don't like using C<get_column>, you can always create an accessor for |
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241 | any of your aliases using either of these: |
242 | |
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243 | # Define accessor manually: |
244 | sub name_length { shift->get_column('name_length'); } |
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245 | |
bade79c4 |
246 | # Or use DBIx::Class::AccessorGroup: |
247 | __PACKAGE__->mk_group_accessors('column' => 'name_length'); |
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248 | |
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249 | =head2 SELECT DISTINCT with multiple columns |
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250 | |
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251 | my $rs = $schema->resultset('Foo')->search( |
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252 | {}, |
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253 | { |
254 | select => [ |
255 | { distinct => [ $source->columns ] } |
256 | ], |
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257 | as => [ $source->columns ] # remember 'as' is not the same as SQL AS :-) |
bade79c4 |
258 | } |
259 | ); |
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260 | |
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261 | =head2 SELECT COUNT(DISTINCT colname) |
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262 | |
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263 | my $rs = $schema->resultset('Foo')->search( |
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264 | {}, |
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265 | { |
266 | select => [ |
267 | { count => { distinct => 'colname' } } |
268 | ], |
269 | as => [ 'count' ] |
270 | } |
271 | ); |
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272 | |
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273 | my $count = $rs->next->get_column('count'); |
274 | |
d2f3e87b |
275 | =head2 Grouping results |
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276 | |
277 | L<DBIx::Class> supports C<GROUP BY> as follows: |
278 | |
279 | my $rs = $schema->resultset('Artist')->search( |
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280 | {}, |
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281 | { |
282 | join => [qw/ cds /], |
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283 | select => [ 'name', { count => 'cds.id' } ], |
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284 | as => [qw/ name cd_count /], |
285 | group_by => [qw/ name /] |
286 | } |
287 | ); |
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288 | |
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289 | # Equivalent SQL: |
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290 | # SELECT name, COUNT( cd.id ) FROM artist |
291 | # LEFT JOIN cd ON artist.id = cd.artist |
bade79c4 |
292 | # GROUP BY name |
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293 | |
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294 | Please see L<DBIx::Class::ResultSet/ATTRIBUTES> documentation if you |
295 | are in any way unsure about the use of the attributes above (C< join |
296 | >, C< select >, C< as > and C< group_by >). |
297 | |
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298 | =head2 Subqueries |
299 | |
300 | You can write subqueries relatively easily in DBIC. |
301 | |
302 | my $inside_rs = $schema->resultset('Artist')->search({ |
303 | name => [ 'Billy Joel', 'Brittany Spears' ], |
304 | }); |
305 | |
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306 | my $rs = $schema->resultset('CD')->search({ |
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307 | artist_id => { 'IN' => $inside_rs->get_column('id')->as_query }, |
308 | }); |
309 | |
310 | The usual operators ( =, !=, IN, NOT IN, etc) are supported. |
311 | |
312 | B<NOTE>: You have to explicitly use '=' when doing an equality comparison. |
313 | The following will B<not> work: |
314 | |
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315 | my $rs = $schema->resultset('CD')->search({ |
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316 | artist_id => $inside_rs->get_column('id')->as_query, |
317 | }); |
318 | |
68a797c1 |
319 | =head3 Correlated subqueries |
320 | |
321 | my $cdrs = $schema->resultset('CD'); |
322 | my $rs = $cdrs->search({ |
323 | year => { |
324 | '=' => $cdrs->search( |
325 | { artistid => { '=' => \'me.artistid' } }, |
326 | { alias => 'inner' } |
327 | )->get_column('year')->max_rs->as_query, |
328 | }, |
329 | }); |
330 | |
331 | That creates the following SQL: |
332 | |
333 | SELECT me.cdid, me.artist, me.title, me.year, me.genreid, me.single_track |
334 | FROM cd me |
335 | WHERE year = ( |
336 | SELECT MAX(inner.year) |
337 | FROM cd inner |
338 | WHERE artistid = me.artistid |
339 | ) |
340 | |
d2f3e87b |
341 | =head2 Predefined searches |
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342 | |
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343 | You can write your own L<DBIx::Class::ResultSet> class by inheriting from it |
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344 | and define often used searches as methods: |
345 | |
346 | package My::DBIC::ResultSet::CD; |
347 | use strict; |
348 | use warnings; |
349 | use base 'DBIx::Class::ResultSet'; |
350 | |
351 | sub search_cds_ordered { |
352 | my ($self) = @_; |
353 | |
354 | return $self->search( |
355 | {}, |
356 | { order_by => 'name DESC' }, |
357 | ); |
358 | } |
359 | |
360 | 1; |
361 | |
362 | To use your resultset, first tell DBIx::Class to create an instance of it |
363 | for you, in your My::DBIC::Schema::CD class: |
364 | |
9dc1bfce |
365 | # class definition as normal |
366 | __PACKAGE__->load_components(qw/ Core /); |
367 | __PACKAGE__->table('cd'); |
368 | |
369 | # tell DBIC to use the custom ResultSet class |
74dc2edc |
370 | __PACKAGE__->resultset_class('My::DBIC::ResultSet::CD'); |
371 | |
9dc1bfce |
372 | Note that C<resultset_class> must be called after C<load_components> and C<table>, or you will get errors about missing methods. |
373 | |
74dc2edc |
374 | Then call your new method in your code: |
375 | |
376 | my $ordered_cds = $schema->resultset('CD')->search_cds_ordered(); |
377 | |
d2f3e87b |
378 | =head2 Using SQL functions on the left hand side of a comparison |
1c133e22 |
379 | |
380 | Using SQL functions on the left hand side of a comparison is generally |
381 | not a good idea since it requires a scan of the entire table. However, |
382 | it can be accomplished with C<DBIx::Class> when necessary. |
383 | |
384 | If you do not have quoting on, simply include the function in your search |
385 | specification as you would any column: |
386 | |
387 | $rs->search({ 'YEAR(date_of_birth)' => 1979 }); |
388 | |
389 | With quoting on, or for a more portable solution, use the C<where> |
390 | attribute: |
391 | |
392 | $rs->search({}, { where => \'YEAR(date_of_birth) = 1979' }); |
393 | |
394 | =begin hidden |
395 | |
396 | (When the bind args ordering bug is fixed, this technique will be better |
397 | and can replace the one above.) |
398 | |
399 | With quoting on, or for a more portable solution, use the C<where> and |
400 | C<bind> attributes: |
401 | |
402 | $rs->search({}, { |
403 | where => \'YEAR(date_of_birth) = ?', |
404 | bind => [ 1979 ] |
405 | }); |
406 | |
407 | =end hidden |
408 | |
d2f3e87b |
409 | =head1 JOINS AND PREFETCHING |
410 | |
87980de7 |
411 | =head2 Using joins and prefetch |
412 | |
bade79c4 |
413 | You can use the C<join> attribute to allow searching on, or sorting your |
414 | results by, one or more columns in a related table. To return all CDs matching |
415 | a particular artist name: |
ea6309e2 |
416 | |
bade79c4 |
417 | my $rs = $schema->resultset('CD')->search( |
418 | { |
419 | 'artist.name' => 'Bob Marley' |
420 | }, |
421 | { |
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422 | join => 'artist', # join the artist table |
bade79c4 |
423 | } |
424 | ); |
425 | |
426 | # Equivalent SQL: |
427 | # SELECT cd.* FROM cd |
428 | # JOIN artist ON cd.artist = artist.id |
429 | # WHERE artist.name = 'Bob Marley' |
430 | |
431 | If required, you can now sort on any column in the related tables by including |
432 | it in your C<order_by> attribute: |
433 | |
434 | my $rs = $schema->resultset('CD')->search( |
435 | { |
436 | 'artist.name' => 'Bob Marley' |
437 | }, |
438 | { |
51458a6a |
439 | join => 'artist', |
bade79c4 |
440 | order_by => [qw/ artist.name /] |
441 | } |
2f81ed0f |
442 | ); |
ea6309e2 |
443 | |
bade79c4 |
444 | # Equivalent SQL: |
445 | # SELECT cd.* FROM cd |
446 | # JOIN artist ON cd.artist = artist.id |
447 | # WHERE artist.name = 'Bob Marley' |
448 | # ORDER BY artist.name |
ea6309e2 |
449 | |
bade79c4 |
450 | Note that the C<join> attribute should only be used when you need to search or |
451 | sort using columns in a related table. Joining related tables when you only |
452 | need columns from the main table will make performance worse! |
ea6309e2 |
453 | |
bade79c4 |
454 | Now let's say you want to display a list of CDs, each with the name of the |
455 | artist. The following will work fine: |
ea6309e2 |
456 | |
bade79c4 |
457 | while (my $cd = $rs->next) { |
458 | print "CD: " . $cd->title . ", Artist: " . $cd->artist->name; |
459 | } |
ea6309e2 |
460 | |
bade79c4 |
461 | There is a problem however. We have searched both the C<cd> and C<artist> tables |
462 | in our main query, but we have only returned data from the C<cd> table. To get |
463 | the artist name for any of the CD objects returned, L<DBIx::Class> will go back |
464 | to the database: |
ea6309e2 |
465 | |
bade79c4 |
466 | SELECT artist.* FROM artist WHERE artist.id = ? |
ea6309e2 |
467 | |
468 | A statement like the one above will run for each and every CD returned by our |
469 | main query. Five CDs, five extra queries. A hundred CDs, one hundred extra |
470 | queries! |
471 | |
bade79c4 |
472 | Thankfully, L<DBIx::Class> has a C<prefetch> attribute to solve this problem. |
897342e4 |
473 | This allows you to fetch results from related tables in advance: |
ea6309e2 |
474 | |
bade79c4 |
475 | my $rs = $schema->resultset('CD')->search( |
476 | { |
477 | 'artist.name' => 'Bob Marley' |
478 | }, |
479 | { |
51458a6a |
480 | join => 'artist', |
bade79c4 |
481 | order_by => [qw/ artist.name /], |
51458a6a |
482 | prefetch => 'artist' # return artist data too! |
bade79c4 |
483 | } |
484 | ); |
ea6309e2 |
485 | |
bade79c4 |
486 | # Equivalent SQL (note SELECT from both "cd" and "artist"): |
487 | # SELECT cd.*, artist.* FROM cd |
488 | # JOIN artist ON cd.artist = artist.id |
489 | # WHERE artist.name = 'Bob Marley' |
490 | # ORDER BY artist.name |
ea6309e2 |
491 | |
492 | The code to print the CD list remains the same: |
493 | |
bade79c4 |
494 | while (my $cd = $rs->next) { |
495 | print "CD: " . $cd->title . ", Artist: " . $cd->artist->name; |
496 | } |
ea6309e2 |
497 | |
bade79c4 |
498 | L<DBIx::Class> has now prefetched all matching data from the C<artist> table, |
ea6309e2 |
499 | so no additional SQL statements are executed. You now have a much more |
500 | efficient query. |
501 | |
77d6b403 |
502 | Note that as of L<DBIx::Class> 0.05999_01, C<prefetch> I<can> be used with |
503 | C<has_many> relationships. |
ea6309e2 |
504 | |
bade79c4 |
505 | Also note that C<prefetch> should only be used when you know you will |
ea6309e2 |
506 | definitely use data from a related table. Pre-fetching related tables when you |
507 | only need columns from the main table will make performance worse! |
508 | |
51458a6a |
509 | =head2 Multiple joins |
510 | |
511 | In the examples above, the C<join> attribute was a scalar. If you |
512 | pass an array reference instead, you can join to multiple tables. In |
513 | this example, we want to limit the search further, using |
514 | C<LinerNotes>: |
515 | |
516 | # Relationships defined elsewhere: |
517 | # CD->belongs_to('artist' => 'Artist'); |
518 | # CD->has_one('liner_notes' => 'LinerNotes', 'cd'); |
519 | my $rs = $schema->resultset('CD')->search( |
520 | { |
521 | 'artist.name' => 'Bob Marley' |
522 | 'liner_notes.notes' => { 'like', '%some text%' }, |
523 | }, |
524 | { |
525 | join => [qw/ artist liner_notes /], |
526 | order_by => [qw/ artist.name /], |
527 | } |
528 | ); |
529 | |
530 | # Equivalent SQL: |
531 | # SELECT cd.*, artist.*, liner_notes.* FROM cd |
532 | # JOIN artist ON cd.artist = artist.id |
533 | # JOIN liner_notes ON cd.id = liner_notes.cd |
534 | # WHERE artist.name = 'Bob Marley' |
535 | # ORDER BY artist.name |
536 | |
d2f3e87b |
537 | =head2 Multi-step joins |
ea6309e2 |
538 | |
539 | Sometimes you want to join more than one relationship deep. In this example, |
bade79c4 |
540 | we want to find all C<Artist> objects who have C<CD>s whose C<LinerNotes> |
541 | contain a specific string: |
542 | |
543 | # Relationships defined elsewhere: |
544 | # Artist->has_many('cds' => 'CD', 'artist'); |
545 | # CD->has_one('liner_notes' => 'LinerNotes', 'cd'); |
546 | |
547 | my $rs = $schema->resultset('Artist')->search( |
548 | { |
549 | 'liner_notes.notes' => { 'like', '%some text%' }, |
550 | }, |
551 | { |
552 | join => { |
553 | 'cds' => 'liner_notes' |
554 | } |
555 | } |
556 | ); |
ea6309e2 |
557 | |
bade79c4 |
558 | # Equivalent SQL: |
559 | # SELECT artist.* FROM artist |
51458a6a |
560 | # LEFT JOIN cd ON artist.id = cd.artist |
561 | # LEFT JOIN liner_notes ON cd.id = liner_notes.cd |
bade79c4 |
562 | # WHERE liner_notes.notes LIKE '%some text%' |
ea6309e2 |
563 | |
564 | Joins can be nested to an arbitrary level. So if we decide later that we |
565 | want to reduce the number of Artists returned based on who wrote the liner |
566 | notes: |
567 | |
bade79c4 |
568 | # Relationship defined elsewhere: |
569 | # LinerNotes->belongs_to('author' => 'Person'); |
570 | |
571 | my $rs = $schema->resultset('Artist')->search( |
572 | { |
573 | 'liner_notes.notes' => { 'like', '%some text%' }, |
574 | 'author.name' => 'A. Writer' |
575 | }, |
576 | { |
577 | join => { |
578 | 'cds' => { |
579 | 'liner_notes' => 'author' |
ea6309e2 |
580 | } |
bade79c4 |
581 | } |
582 | } |
583 | ); |
ea6309e2 |
584 | |
bade79c4 |
585 | # Equivalent SQL: |
586 | # SELECT artist.* FROM artist |
51458a6a |
587 | # LEFT JOIN cd ON artist.id = cd.artist |
588 | # LEFT JOIN liner_notes ON cd.id = liner_notes.cd |
589 | # LEFT JOIN author ON author.id = liner_notes.author |
bade79c4 |
590 | # WHERE liner_notes.notes LIKE '%some text%' |
591 | # AND author.name = 'A. Writer' |
87980de7 |
592 | |
51458a6a |
593 | =head2 Multi-step and multiple joins |
594 | |
595 | With various combinations of array and hash references, you can join |
596 | tables in any combination you desire. For example, to join Artist to |
597 | CD and Concert, and join CD to LinerNotes: |
598 | |
599 | # Relationships defined elsewhere: |
600 | # Artist->has_many('concerts' => 'Concert', 'artist'); |
601 | |
602 | my $rs = $schema->resultset('Artist')->search( |
603 | { }, |
604 | { |
605 | join => [ |
606 | { |
607 | cds => 'liner_notes' |
608 | }, |
609 | 'concerts' |
610 | ], |
611 | } |
612 | ); |
613 | |
614 | # Equivalent SQL: |
615 | # SELECT artist.* FROM artist |
616 | # LEFT JOIN cd ON artist.id = cd.artist |
617 | # LEFT JOIN liner_notes ON cd.id = liner_notes.cd |
618 | # LEFT JOIN concert ON artist.id = concert.artist |
619 | |
897342e4 |
620 | =head2 Multi-step prefetch |
621 | |
622 | From 0.04999_05 onwards, C<prefetch> can be nested more than one relationship |
623 | deep using the same syntax as a multi-step join: |
624 | |
625 | my $rs = $schema->resultset('Tag')->search( |
ac2803ef |
626 | {}, |
897342e4 |
627 | { |
628 | prefetch => { |
629 | cd => 'artist' |
630 | } |
631 | } |
632 | ); |
633 | |
634 | # Equivalent SQL: |
635 | # SELECT tag.*, cd.*, artist.* FROM tag |
51458a6a |
636 | # JOIN cd ON tag.cd = cd.id |
637 | # JOIN artist ON cd.artist = artist.id |
897342e4 |
638 | |
639 | Now accessing our C<cd> and C<artist> relationships does not need additional |
640 | SQL statements: |
641 | |
642 | my $tag = $rs->first; |
643 | print $tag->cd->artist->name; |
644 | |
d2f3e87b |
645 | =head1 ROW-LEVEL OPERATIONS |
646 | |
647 | =head2 Retrieving a row object's Schema |
648 | |
649 | It is possible to get a Schema object from a row object like so: |
650 | |
651 | my $schema = $cd->result_source->schema; |
652 | # use the schema as normal: |
653 | my $artist_rs = $schema->resultset('Artist'); |
654 | |
655 | This can be useful when you don't want to pass around a Schema object to every |
656 | method. |
657 | |
658 | =head2 Getting the value of the primary key for the last database insert |
659 | |
660 | AKA getting last_insert_id |
661 | |
662 | If you are using PK::Auto (which is a core component as of 0.07), this is |
663 | straightforward: |
664 | |
665 | my $foo = $rs->create(\%blah); |
666 | # do more stuff |
667 | my $id = $foo->id; # foo->my_primary_key_field will also work. |
668 | |
669 | If you are not using autoincrementing primary keys, this will probably |
670 | not work, but then you already know the value of the last primary key anyway. |
671 | |
672 | =head2 Stringification |
673 | |
674 | Employ the standard stringification technique by using the C<overload> |
675 | module. |
676 | |
677 | To make an object stringify itself as a single column, use something |
678 | like this (replace C<foo> with the column/method of your choice): |
679 | |
680 | use overload '""' => sub { shift->name}, fallback => 1; |
681 | |
682 | For more complex stringification, you can use an anonymous subroutine: |
683 | |
684 | use overload '""' => sub { $_[0]->name . ", " . |
685 | $_[0]->address }, fallback => 1; |
686 | |
687 | =head3 Stringification Example |
688 | |
689 | Suppose we have two tables: C<Product> and C<Category>. The table |
690 | specifications are: |
691 | |
692 | Product(id, Description, category) |
693 | Category(id, Description) |
694 | |
695 | C<category> is a foreign key into the Category table. |
696 | |
697 | If you have a Product object C<$obj> and write something like |
698 | |
699 | print $obj->category |
700 | |
701 | things will not work as expected. |
702 | |
703 | To obtain, for example, the category description, you should add this |
704 | method to the class defining the Category table: |
705 | |
706 | use overload "" => sub { |
707 | my $self = shift; |
708 | |
709 | return $self->Description; |
710 | }, fallback => 1; |
711 | |
712 | =head2 Want to know if find_or_create found or created a row? |
713 | |
714 | Just use C<find_or_new> instead, then check C<in_storage>: |
715 | |
716 | my $obj = $rs->find_or_new({ blah => 'blarg' }); |
717 | unless ($obj->in_storage) { |
718 | $obj->insert; |
719 | # do whatever else you wanted if it was a new row |
720 | } |
721 | |
722 | =head2 Dynamic Sub-classing DBIx::Class proxy classes |
723 | |
724 | AKA multi-class object inflation from one table |
725 | |
726 | L<DBIx::Class> classes are proxy classes, therefore some different |
727 | techniques need to be employed for more than basic subclassing. In |
728 | this example we have a single user table that carries a boolean bit |
729 | for admin. We would like like to give the admin users |
730 | objects(L<DBIx::Class::Row>) the same methods as a regular user but |
731 | also special admin only methods. It doesn't make sense to create two |
732 | seperate proxy-class files for this. We would be copying all the user |
733 | methods into the Admin class. There is a cleaner way to accomplish |
734 | this. |
735 | |
736 | Overriding the C<inflate_result> method within the User proxy-class |
737 | gives us the effect we want. This method is called by |
738 | L<DBIx::Class::ResultSet> when inflating a result from storage. So we |
739 | grab the object being returned, inspect the values we are looking for, |
740 | bless it if it's an admin object, and then return it. See the example |
741 | below: |
742 | |
743 | B<Schema Definition> |
744 | |
745 | package DB::Schema; |
746 | |
747 | use base qw/DBIx::Class::Schema/; |
748 | |
749 | __PACKAGE__->load_classes(qw/User/); |
750 | |
751 | |
752 | B<Proxy-Class definitions> |
753 | |
754 | package DB::Schema::User; |
755 | |
756 | use strict; |
757 | use warnings; |
758 | use base qw/DBIx::Class/; |
759 | |
760 | ### Defined what our admin class is for ensure_class_loaded |
761 | my $admin_class = __PACKAGE__ . '::Admin'; |
762 | |
763 | __PACKAGE__->load_components(qw/Core/); |
764 | |
765 | __PACKAGE__->table('users'); |
766 | |
767 | __PACKAGE__->add_columns(qw/user_id email password |
768 | firstname lastname active |
769 | admin/); |
770 | |
771 | __PACKAGE__->set_primary_key('user_id'); |
772 | |
773 | sub inflate_result { |
774 | my $self = shift; |
775 | my $ret = $self->next::method(@_); |
776 | if( $ret->admin ) {### If this is an admin rebless for extra functions |
777 | $self->ensure_class_loaded( $admin_class ); |
778 | bless $ret, $admin_class; |
779 | } |
780 | return $ret; |
781 | } |
782 | |
783 | sub hello { |
784 | print "I am a regular user.\n"; |
785 | return ; |
786 | } |
787 | |
788 | |
789 | package DB::Schema::User::Admin; |
790 | |
791 | use strict; |
792 | use warnings; |
793 | use base qw/DB::Schema::User/; |
794 | |
795 | sub hello |
796 | { |
797 | print "I am an admin.\n"; |
798 | return; |
799 | } |
800 | |
801 | sub do_admin_stuff |
802 | { |
803 | print "I am doing admin stuff\n"; |
804 | return ; |
805 | } |
806 | |
807 | B<Test File> test.pl |
808 | |
809 | use warnings; |
810 | use strict; |
811 | use DB::Schema; |
812 | |
813 | my $user_data = { email => 'someguy@place.com', |
814 | password => 'pass1', |
815 | admin => 0 }; |
816 | |
817 | my $admin_data = { email => 'someadmin@adminplace.com', |
818 | password => 'pass2', |
819 | admin => 1 }; |
820 | |
821 | my $schema = DB::Schema->connection('dbi:Pg:dbname=test'); |
822 | |
823 | $schema->resultset('User')->create( $user_data ); |
824 | $schema->resultset('User')->create( $admin_data ); |
825 | |
826 | ### Now we search for them |
827 | my $user = $schema->resultset('User')->single( $user_data ); |
828 | my $admin = $schema->resultset('User')->single( $admin_data ); |
829 | |
830 | print ref $user, "\n"; |
831 | print ref $admin, "\n"; |
832 | |
833 | print $user->password , "\n"; # pass1 |
834 | print $admin->password , "\n";# pass2; inherited from User |
835 | print $user->hello , "\n";# I am a regular user. |
836 | print $admin->hello, "\n";# I am an admin. |
837 | |
838 | ### The statement below will NOT print |
839 | print "I can do admin stuff\n" if $user->can('do_admin_stuff'); |
840 | ### The statement below will print |
841 | print "I can do admin stuff\n" if $admin->can('do_admin_stuff'); |
842 | |
a5b29361 |
843 | =head2 Skip row object creation for faster results |
d2f3e87b |
844 | |
845 | DBIx::Class is not built for speed, it's built for convenience and |
846 | ease of use, but sometimes you just need to get the data, and skip the |
847 | fancy objects. |
848 | |
849 | To do this simply use L<DBIx::Class::ResultClass::HashRefInflator>. |
850 | |
851 | my $rs = $schema->resultset('CD'); |
852 | |
853 | $rs->result_class('DBIx::Class::ResultClass::HashRefInflator'); |
854 | |
855 | my $hash_ref = $rs->find(1); |
a5b29361 |
856 | |
d2f3e87b |
857 | Wasn't that easy? |
bc96f260 |
858 | |
d2f3e87b |
859 | =head2 Get raw data for blindingly fast results |
860 | |
861 | If the L<HashRefInflator|DBIx::Class::ResultClass::HashRefInflator> solution |
862 | above is not fast enough for you, you can use a DBIx::Class to return values |
863 | exactly as they come out of the data base with none of the convenience methods |
864 | wrapped round them. |
865 | |
2d7d8459 |
866 | This is used like so: |
d2f3e87b |
867 | |
868 | my $cursor = $rs->cursor |
869 | while (my @vals = $cursor->next) { |
870 | # use $val[0..n] here |
871 | } |
872 | |
873 | You will need to map the array offsets to particular columns (you can |
874 | use the I<select> attribute of C<search()> to force ordering). |
875 | |
876 | =head1 RESULTSET OPERATIONS |
877 | |
878 | =head2 Getting Schema from a ResultSet |
879 | |
880 | To get the schema object from a result set, do the following: |
881 | |
882 | $rs->result_source->schema |
883 | |
884 | =head2 Getting Columns Of Data |
885 | |
886 | AKA Aggregating Data |
ac2803ef |
887 | |
888 | If you want to find the sum of a particular column there are several |
889 | ways, the obvious one is to use search: |
890 | |
891 | my $rs = $schema->resultset('Items')->search( |
892 | {}, |
893 | { |
894 | select => [ { sum => 'Cost' } ], |
d676881f |
895 | as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL |
ac2803ef |
896 | } |
897 | ); |
898 | my $tc = $rs->first->get_column('total_cost'); |
899 | |
900 | Or, you can use the L<DBIx::Class::ResultSetColumn>, which gets |
901 | returned when you ask the C<ResultSet> for a column using |
902 | C<get_column>: |
903 | |
904 | my $cost = $schema->resultset('Items')->get_column('Cost'); |
905 | my $tc = $cost->sum; |
906 | |
907 | With this you can also do: |
908 | |
909 | my $minvalue = $cost->min; |
910 | my $maxvalue = $cost->max; |
911 | |
912 | Or just iterate through the values of this column only: |
913 | |
914 | while ( my $c = $cost->next ) { |
915 | print $c; |
916 | } |
917 | |
918 | foreach my $c ($cost->all) { |
919 | print $c; |
920 | } |
921 | |
709353af |
922 | C<ResultSetColumn> only has a limited number of built-in functions, if |
923 | you need one that it doesn't have, then you can use the C<func> method |
924 | instead: |
925 | |
926 | my $avg = $cost->func('AVERAGE'); |
927 | |
928 | This will cause the following SQL statement to be run: |
929 | |
930 | SELECT AVERAGE(Cost) FROM Items me |
931 | |
932 | Which will of course only work if your database supports this function. |
ac2803ef |
933 | See L<DBIx::Class::ResultSetColumn> for more documentation. |
934 | |
204e5c03 |
935 | =head2 Creating a result set from a set of rows |
936 | |
937 | Sometimes you have a (set of) row objects that you want to put into a |
938 | resultset without the need to hit the DB again. You can do that by using the |
939 | L<set_cache|DBIx::Class::Resultset/set_cache> method: |
940 | |
2d7a4e46 |
941 | my @uploadable_groups; |
204e5c03 |
942 | while (my $group = $groups->next) { |
943 | if ($group->can_upload($self)) { |
944 | push @uploadable_groups, $group; |
945 | } |
946 | } |
947 | my $new_rs = $self->result_source->resultset; |
948 | $new_rs->set_cache(\@uploadable_groups); |
949 | return $new_rs; |
950 | |
951 | |
d2f3e87b |
952 | =head1 USING RELATIONSHIPS |
acee4e4d |
953 | |
d2f3e87b |
954 | =head2 Create a new row in a related table |
acee4e4d |
955 | |
6f1434fd |
956 | my $author = $book->create_related('author', { name => 'Fred'}); |
acee4e4d |
957 | |
d2f3e87b |
958 | =head2 Search in a related table |
acee4e4d |
959 | |
960 | Only searches for books named 'Titanic' by the author in $author. |
961 | |
6f1434fd |
962 | my $books_rs = $author->search_related('books', { name => 'Titanic' }); |
acee4e4d |
963 | |
d2f3e87b |
964 | =head2 Delete data in a related table |
acee4e4d |
965 | |
966 | Deletes only the book named Titanic by the author in $author. |
967 | |
6f1434fd |
968 | $author->delete_related('books', { name => 'Titanic' }); |
acee4e4d |
969 | |
d2f3e87b |
970 | =head2 Ordering a relationship result set |
f8bad769 |
971 | |
972 | If you always want a relation to be ordered, you can specify this when you |
973 | create the relationship. |
974 | |
6f1434fd |
975 | To order C<< $book->pages >> by descending page_number, create the relation |
976 | as follows: |
f8bad769 |
977 | |
6f1434fd |
978 | __PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => \'page_number DESC'} ); |
f8bad769 |
979 | |
7c0825ab |
980 | =head2 Filtering a relationship result set |
981 | |
982 | If you want to get a filtered result set, you can just add add to $attr as follows: |
983 | |
984 | __PACKAGE__->has_many('pages' => 'Page', 'book', { where => { scrap => 0 } } ); |
985 | |
d2f3e87b |
986 | =head2 Many-to-many relationships |
f8bad769 |
987 | |
d2f3e87b |
988 | This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>: |
f8bad769 |
989 | |
d2f3e87b |
990 | package My::User; |
6f1434fd |
991 | use base 'DBIx::Class'; |
992 | __PACKAGE__->load_components('Core'); |
d2f3e87b |
993 | __PACKAGE__->table('user'); |
994 | __PACKAGE__->add_columns(qw/id name/); |
995 | __PACKAGE__->set_primary_key('id'); |
996 | __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'user'); |
997 | __PACKAGE__->many_to_many('addresses' => 'user_address', 'address'); |
87980de7 |
998 | |
d2f3e87b |
999 | package My::UserAddress; |
6f1434fd |
1000 | use base 'DBIx::Class'; |
1001 | __PACKAGE__->load_components('Core'); |
d2f3e87b |
1002 | __PACKAGE__->table('user_address'); |
1003 | __PACKAGE__->add_columns(qw/user address/); |
1004 | __PACKAGE__->set_primary_key(qw/user address/); |
1005 | __PACKAGE__->belongs_to('user' => 'My::User'); |
1006 | __PACKAGE__->belongs_to('address' => 'My::Address'); |
181a28f4 |
1007 | |
d2f3e87b |
1008 | package My::Address; |
6f1434fd |
1009 | use base 'DBIx::Class'; |
1010 | __PACKAGE__->load_components('Core'); |
d2f3e87b |
1011 | __PACKAGE__->table('address'); |
1012 | __PACKAGE__->add_columns(qw/id street town area_code country/); |
1013 | __PACKAGE__->set_primary_key('id'); |
1014 | __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'address'); |
1015 | __PACKAGE__->many_to_many('users' => 'user_address', 'user'); |
1016 | |
1017 | $rs = $user->addresses(); # get all addresses for a user |
1018 | $rs = $address->users(); # get all users for an address |
1019 | |
1020 | =head1 TRANSACTIONS |
1021 | |
1022 | As of version 0.04001, there is improved transaction support in |
1023 | L<DBIx::Class::Storage> and L<DBIx::Class::Schema>. Here is an |
1024 | example of the recommended way to use it: |
1025 | |
1026 | my $genus = $schema->resultset('Genus')->find(12); |
1027 | |
1028 | my $coderef2 = sub { |
1029 | $genus->extinct(1); |
1030 | $genus->update; |
1031 | }; |
70634260 |
1032 | |
181a28f4 |
1033 | my $coderef1 = sub { |
35d4fe78 |
1034 | $genus->add_to_species({ name => 'troglodyte' }); |
1035 | $genus->wings(2); |
1036 | $genus->update; |
6f1434fd |
1037 | $schema->txn_do($coderef2); # Can have a nested transaction. Only the outer will actualy commit |
181a28f4 |
1038 | return $genus->species; |
1039 | }; |
1040 | |
181a28f4 |
1041 | my $rs; |
1042 | eval { |
70634260 |
1043 | $rs = $schema->txn_do($coderef1); |
181a28f4 |
1044 | }; |
1045 | |
1046 | if ($@) { # Transaction failed |
1047 | die "the sky is falling!" # |
1048 | if ($@ =~ /Rollback failed/); # Rollback failed |
1049 | |
1050 | deal_with_failed_transaction(); |
35d4fe78 |
1051 | } |
87980de7 |
1052 | |
181a28f4 |
1053 | Nested transactions will work as expected. That is, only the outermost |
1054 | transaction will actually issue a commit to the $dbh, and a rollback |
1055 | at any level of any transaction will cause the entire nested |
1056 | transaction to fail. Support for savepoints and for true nested |
40dbc108 |
1057 | transactions (for databases that support them) will hopefully be added |
1058 | in the future. |
ee38fa40 |
1059 | |
d2f3e87b |
1060 | =head1 SQL |
ee38fa40 |
1061 | |
d2f3e87b |
1062 | =head2 Creating Schemas From An Existing Database |
ea6309e2 |
1063 | |
d2f3e87b |
1064 | L<DBIx::Class::Schema::Loader> will connect to a database and create a |
1065 | L<DBIx::Class::Schema> and associated sources by examining the database. |
bade79c4 |
1066 | |
d2f3e87b |
1067 | The recommend way of achieving this is to use the |
1068 | L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> method: |
bade79c4 |
1069 | |
6f1434fd |
1070 | perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:./lib \ |
1071 | -e 'make_schema_at("My::Schema", { debug => 1 }, [ "dbi:Pg:dbname=foo","postgres" ])' |
362500af |
1072 | |
d2f3e87b |
1073 | This will create a tree of files rooted at C<./lib/My/Schema/> containing |
1074 | source definitions for all the tables found in the C<foo> database. |
362500af |
1075 | |
d2f3e87b |
1076 | =head2 Creating DDL SQL |
362500af |
1077 | |
264f1571 |
1078 | The following functionality requires you to have L<SQL::Translator> |
1079 | (also known as "SQL Fairy") installed. |
362500af |
1080 | |
264f1571 |
1081 | To create a set of database-specific .sql files for the above schema: |
362500af |
1082 | |
264f1571 |
1083 | my $schema = My::Schema->connect($dsn); |
1084 | $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'], |
1085 | '0.1', |
d2f3e87b |
1086 | './dbscriptdir/' |
264f1571 |
1087 | ); |
1088 | |
1089 | By default this will create schema files in the current directory, for |
1090 | MySQL, SQLite and PostgreSQL, using the $VERSION from your Schema.pm. |
1091 | |
1092 | To create a new database using the schema: |
1093 | |
1094 | my $schema = My::Schema->connect($dsn); |
1095 | $schema->deploy({ add_drop_tables => 1}); |
1096 | |
1097 | To import created .sql files using the mysql client: |
1098 | |
1099 | mysql -h "host" -D "database" -u "user" -p < My_Schema_1.0_MySQL.sql |
1100 | |
1101 | To create C<ALTER TABLE> conversion scripts to update a database to a |
1102 | newer version of your schema at a later point, first set a new |
d2f3e87b |
1103 | C<$VERSION> in your Schema file, then: |
264f1571 |
1104 | |
1105 | my $schema = My::Schema->connect($dsn); |
1106 | $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'], |
1107 | '0.2', |
1108 | '/dbscriptdir/', |
1109 | '0.1' |
1110 | ); |
1111 | |
1112 | This will produce new database-specific .sql files for the new version |
1113 | of the schema, plus scripts to convert from version 0.1 to 0.2. This |
1114 | requires that the files for 0.1 as created above are available in the |
1115 | given directory to diff against. |
362500af |
1116 | |
6f1434fd |
1117 | =head2 Select from dual |
16cd5b28 |
1118 | |
1119 | Dummy tables are needed by some databases to allow calling functions |
1120 | or expressions that aren't based on table content, for examples of how |
1121 | this applies to various database types, see: |
1122 | L<http://troels.arvin.dk/db/rdbms/#other-dummy_table>. |
1123 | |
1124 | Note: If you're using Oracles dual table don't B<ever> do anything |
1125 | other than a select, if you CRUD on your dual table you *will* break |
1126 | your database. |
1127 | |
1128 | Make a table class as you would for any other table |
1129 | |
1130 | package MyAppDB::Dual; |
1131 | use strict; |
1132 | use warnings; |
1133 | use base 'DBIx::Class'; |
1134 | __PACKAGE__->load_components("Core"); |
1135 | __PACKAGE__->table("Dual"); |
1136 | __PACKAGE__->add_columns( |
1137 | "dummy", |
1138 | { data_type => "VARCHAR2", is_nullable => 0, size => 1 }, |
1139 | ); |
1140 | |
1141 | Once you've loaded your table class select from it using C<select> |
1142 | and C<as> instead of C<columns> |
1143 | |
1144 | my $rs = $schema->resultset('Dual')->search(undef, |
1145 | { select => [ 'sydate' ], |
1146 | as => [ 'now' ] |
1147 | }, |
1148 | ); |
1149 | |
1150 | All you have to do now is be careful how you access your resultset, the below |
1151 | will not work because there is no column called 'now' in the Dual table class |
1152 | |
1153 | while (my $dual = $rs->next) { |
1154 | print $dual->now."\n"; |
1155 | } |
6f1434fd |
1156 | # Can't locate object method "now" via package "MyAppDB::Dual" at headshot.pl line 23. |
16cd5b28 |
1157 | |
1158 | You could of course use 'dummy' in C<as> instead of 'now', or C<add_columns> to |
1159 | your Dual class for whatever you wanted to select from dual, but that's just |
1160 | silly, instead use C<get_column> |
1161 | |
1162 | while (my $dual = $rs->next) { |
1163 | print $dual->get_column('now')."\n"; |
1164 | } |
1165 | |
1166 | Or use C<cursor> |
1167 | |
1168 | my $cursor = $rs->cursor; |
1169 | while (my @vals = $cursor->next) { |
1170 | print $vals[0]."\n"; |
1171 | } |
1172 | |
1173 | Or use L<DBIx::Class::ResultClass::HashRefInflator> |
1174 | |
1175 | $rs->result_class('DBIx::Class::ResultClass::HashRefInflator'); |
1176 | while ( my $dual = $rs->next ) { |
1177 | print $dual->{now}."\n"; |
1178 | } |
1179 | |
1180 | Here are some example C<select> conditions to illustrate the different syntax |
1181 | you could use for doing stuff like |
1182 | C<oracles.heavily(nested(functions_can('take', 'lots'), OF), 'args')> |
1183 | |
1184 | # get a sequence value |
1185 | select => [ 'A_SEQ.nextval' ], |
1186 | |
1187 | # get create table sql |
1188 | select => [ { 'dbms_metadata.get_ddl' => [ "'TABLE'", "'ARTIST'" ]} ], |
1189 | |
1190 | # get a random num between 0 and 100 |
1191 | select => [ { "trunc" => [ { "dbms_random.value" => [0,100] } ]} ], |
1192 | |
1193 | # what year is it? |
1194 | select => [ { 'extract' => [ \'year from sysdate' ] } ], |
1195 | |
1196 | # do some math |
1197 | select => [ {'round' => [{'cos' => [ \'180 * 3.14159265359/180' ]}]}], |
1198 | |
1199 | # which day of the week were you born on? |
6f1434fd |
1200 | select => [{'to_char' => [{'to_date' => [ "'25-DEC-1980'", "'dd-mon-yyyy'" ]}, "'day'"]}], |
16cd5b28 |
1201 | |
1202 | # select 16 rows from dual |
1203 | select => [ "'hello'" ], |
1204 | as => [ 'world' ], |
1205 | group_by => [ 'cube( 1, 2, 3, 4 )' ], |
1206 | |
1207 | |
1208 | |
d2f3e87b |
1209 | =head2 Adding Indexes And Functions To Your SQL |
362500af |
1210 | |
d2f3e87b |
1211 | Often you will want indexes on columns on your table to speed up searching. To |
1212 | do this, create a method called C<sqlt_deploy_hook> in the relevant source |
2d7d8459 |
1213 | class (refer to the advanced |
1214 | L<callback system|DBIx::Class::ResultSource/sqlt_deploy_callback> if you wish |
1215 | to share a hook between multiple sources): |
b0a20454 |
1216 | |
d2f3e87b |
1217 | package My::Schema::Artist; |
b0a20454 |
1218 | |
d2f3e87b |
1219 | __PACKAGE__->table('artist'); |
1220 | __PACKAGE__->add_columns(id => { ... }, name => { ... }) |
b0a20454 |
1221 | |
d2f3e87b |
1222 | sub sqlt_deploy_hook { |
1223 | my ($self, $sqlt_table) = @_; |
1224 | |
1225 | $sqlt_table->add_index(name => 'idx_name', fields => ['name']); |
1226 | } |
1227 | |
1228 | 1; |
1229 | |
1230 | Sometimes you might want to change the index depending on the type of the |
1231 | database for which SQL is being generated: |
1232 | |
1233 | my ($db_type = $sqlt_table->schema->translator->producer_type) |
1234 | =~ s/^SQL::Translator::Producer:://; |
1235 | |
1236 | You can also add hooks to the schema level to stop certain tables being |
1237 | created: |
1238 | |
1239 | package My::Schema; |
1240 | |
1241 | ... |
1242 | |
1243 | sub sqlt_deploy_hook { |
1244 | my ($self, $sqlt_schema) = @_; |
1245 | |
1246 | $sqlt_schema->drop_table('table_name'); |
1247 | } |
1248 | |
2d7d8459 |
1249 | You could also add views, procedures or triggers to the output using |
1250 | L<SQL::Translator::Schema/add_view>, |
1251 | L<SQL::Translator::Schema/add_procedure> or |
1252 | L<SQL::Translator::Schema/add_trigger>. |
1253 | |
b0a20454 |
1254 | |
362500af |
1255 | =head2 Schema versioning |
1256 | |
1257 | The following example shows simplistically how you might use DBIx::Class to |
1258 | deploy versioned schemas to your customers. The basic process is as follows: |
1259 | |
da4779ad |
1260 | =over 4 |
1261 | |
1262 | =item 1. |
1263 | |
1264 | Create a DBIx::Class schema |
1265 | |
1266 | =item 2. |
1267 | |
1268 | Save the schema |
1269 | |
1270 | =item 3. |
1271 | |
1272 | Deploy to customers |
1273 | |
1274 | =item 4. |
1275 | |
1276 | Modify schema to change functionality |
1277 | |
1278 | =item 5. |
1279 | |
1280 | Deploy update to customers |
1281 | |
1282 | =back |
362500af |
1283 | |
d2f3e87b |
1284 | B<Create a DBIx::Class schema> |
362500af |
1285 | |
1286 | This can either be done manually, or generated from an existing database as |
d2f3e87b |
1287 | described under L</Creating Schemas From An Existing Database> |
362500af |
1288 | |
d2f3e87b |
1289 | B<Save the schema> |
362500af |
1290 | |
d2f3e87b |
1291 | Call L<DBIx::Class::Schema/create_ddl_dir> as above under L</Creating DDL SQL>. |
362500af |
1292 | |
d2f3e87b |
1293 | B<Deploy to customers> |
362500af |
1294 | |
1295 | There are several ways you could deploy your schema. These are probably |
1296 | beyond the scope of this recipe, but might include: |
1297 | |
da4779ad |
1298 | =over 4 |
1299 | |
1300 | =item 1. |
1301 | |
1302 | Require customer to apply manually using their RDBMS. |
1303 | |
1304 | =item 2. |
1305 | |
1306 | Package along with your app, making database dump/schema update/tests |
362500af |
1307 | all part of your install. |
1308 | |
da4779ad |
1309 | =back |
1310 | |
d2f3e87b |
1311 | B<Modify the schema to change functionality> |
362500af |
1312 | |
264f1571 |
1313 | As your application evolves, it may be necessary to modify your schema |
1314 | to change functionality. Once the changes are made to your schema in |
1315 | DBIx::Class, export the modified schema and the conversion scripts as |
d2f3e87b |
1316 | in L</Creating DDL SQL>. |
362500af |
1317 | |
d2f3e87b |
1318 | B<Deploy update to customers> |
362500af |
1319 | |
264f1571 |
1320 | Add the L<DBIx::Class::Schema::Versioned> schema component to your |
1321 | Schema class. This will add a new table to your database called |
ecea7937 |
1322 | C<dbix_class_schema_vesion> which will keep track of which version is installed |
264f1571 |
1323 | and warn if the user trys to run a newer schema version than the |
1324 | database thinks it has. |
1325 | |
1326 | Alternatively, you can send the conversion sql scripts to your |
1327 | customers as above. |
362500af |
1328 | |
d2f3e87b |
1329 | =head2 Setting quoting for the generated SQL. |
1330 | |
1331 | If the database contains column names with spaces and/or reserved words, they |
1332 | need to be quoted in the SQL queries. This is done using: |
1333 | |
1334 | __PACKAGE__->storage->sql_maker->quote_char([ qw/[ ]/] ); |
1335 | __PACKAGE__->storage->sql_maker->name_sep('.'); |
1336 | |
1337 | The first sets the quote characters. Either a pair of matching |
1338 | brackets, or a C<"> or C<'>: |
1339 | |
1340 | __PACKAGE__->storage->sql_maker->quote_char('"'); |
1341 | |
1342 | Check the documentation of your database for the correct quote |
1343 | characters to use. C<name_sep> needs to be set to allow the SQL |
1344 | generator to put the quotes the correct place. |
1345 | |
1346 | In most cases you should set these as part of the arguments passed to |
d68b0c69 |
1347 | L<DBIx::Class::Schema/connect>: |
d2f3e87b |
1348 | |
1349 | my $schema = My::Schema->connect( |
1350 | 'dbi:mysql:my_db', |
1351 | 'db_user', |
1352 | 'db_password', |
1353 | { |
1354 | quote_char => '"', |
1355 | name_sep => '.' |
1356 | } |
1357 | ) |
1358 | |
7be93b07 |
1359 | =head2 Setting limit dialect for SQL::Abstract::Limit |
1360 | |
324572ca |
1361 | In some cases, SQL::Abstract::Limit cannot determine the dialect of |
1362 | the remote SQL server by looking at the database handle. This is a |
1363 | common problem when using the DBD::JDBC, since the DBD-driver only |
1364 | know that in has a Java-driver available, not which JDBC driver the |
1365 | Java component has loaded. This specifically sets the limit_dialect |
1366 | to Microsoft SQL-server (See more names in SQL::Abstract::Limit |
1367 | -documentation. |
7be93b07 |
1368 | |
1369 | __PACKAGE__->storage->sql_maker->limit_dialect('mssql'); |
1370 | |
324572ca |
1371 | The JDBC bridge is one way of getting access to a MSSQL server from a platform |
7be93b07 |
1372 | that Microsoft doesn't deliver native client libraries for. (e.g. Linux) |
1373 | |
d2f3e87b |
1374 | The limit dialect can also be set at connect time by specifying a |
1375 | C<limit_dialect> key in the final hash as shown above. |
2437a1e3 |
1376 | |
05697a49 |
1377 | =head2 Working with PostgreSQL array types |
1378 | |
1379 | If your SQL::Abstract version (>= 1.50) supports it, you can assign to |
1380 | PostgreSQL array values by passing array references in the C<\%columns> |
1381 | (C<\%vals>) hashref of the L<DBIx::Class::ResultSet/create> and |
1382 | L<DBIx::Class::Row/update> family of methods: |
1383 | |
1384 | $resultset->create({ |
1385 | numbers => [1, 2, 3] |
1386 | }); |
1387 | |
1388 | $row->update( |
1389 | { |
1390 | numbers => [1, 2, 3] |
1391 | }, |
1392 | { |
1393 | day => '2008-11-24' |
1394 | } |
1395 | ); |
1396 | |
1397 | In conditions (eg. C<\%cond> in the L<DBIx::Class::ResultSet/search> family of |
1398 | methods) you cannot directly use array references (since this is interpreted as |
1399 | a list of values to be C<OR>ed), but you can use the following syntax to force |
1400 | passing them as bind values: |
1401 | |
1402 | $resultset->search( |
1403 | { |
31eb3263 |
1404 | numbers => \[ '= ?', [numbers => [1, 2, 3]] ] |
05697a49 |
1405 | } |
1406 | ); |
1407 | |
1408 | See L<SQL::Abstract/array_datatypes> and L<SQL::Abstract/Literal SQL with |
31eb3263 |
1409 | placeholders and bind values (subqueries)> for more explanation. Note that |
1410 | L<DBIx::Class> sets L<SQL::Abstract/bindtype> to C<columns>, so you must pass |
1411 | the bind values (the C<[1, 2, 3]> arrayref in the above example) wrapped in |
1412 | arrayrefs together with the column name, like this: C<< [column_name => value] |
1413 | >>. |
05697a49 |
1414 | |
d2f3e87b |
1415 | =head1 BOOTSTRAPPING/MIGRATING |
2437a1e3 |
1416 | |
d2f3e87b |
1417 | =head2 Easy migration from class-based to schema-based setup |
2437a1e3 |
1418 | |
d2f3e87b |
1419 | You want to start using the schema-based approach to L<DBIx::Class> |
1420 | (see L<SchemaIntro.pod>), but have an established class-based setup with lots |
1421 | of existing classes that you don't want to move by hand. Try this nifty script |
1422 | instead: |
1423 | |
1424 | use MyDB; |
1425 | use SQL::Translator; |
1426 | |
1427 | my $schema = MyDB->schema_instance; |
2437a1e3 |
1428 | |
d2f3e87b |
1429 | my $translator = SQL::Translator->new( |
1430 | debug => $debug || 0, |
1431 | trace => $trace || 0, |
1432 | no_comments => $no_comments || 0, |
1433 | show_warnings => $show_warnings || 0, |
1434 | add_drop_table => $add_drop_table || 0, |
1435 | validate => $validate || 0, |
1436 | parser_args => { |
1437 | 'DBIx::Schema' => $schema, |
1438 | }, |
1439 | producer_args => { |
1440 | 'prefix' => 'My::Schema', |
1441 | }, |
1442 | ); |
1443 | |
1444 | $translator->parser('SQL::Translator::Parser::DBIx::Class'); |
1445 | $translator->producer('SQL::Translator::Producer::DBIx::Class::File'); |
1446 | |
1447 | my $output = $translator->translate(@args) or die |
1448 | "Error: " . $translator->error; |
1449 | |
1450 | print $output; |
2437a1e3 |
1451 | |
d2f3e87b |
1452 | You could use L<Module::Find> to search for all subclasses in the MyDB::* |
1453 | namespace, which is currently left as an exercise for the reader. |
2437a1e3 |
1454 | |
d2f3e87b |
1455 | =head1 OVERLOADING METHODS |
086b93a2 |
1456 | |
ab872312 |
1457 | L<DBIx::Class> uses the L<Class::C3> package, which provides for redispatch of |
1458 | method calls, useful for things like default values and triggers. You have to |
1459 | use calls to C<next::method> to overload methods. More information on using |
1460 | L<Class::C3> with L<DBIx::Class> can be found in |
086b93a2 |
1461 | L<DBIx::Class::Manual::Component>. |
1462 | |
d2f3e87b |
1463 | =head2 Setting default values for a row |
1464 | |
1465 | It's as simple as overriding the C<new> method. Note the use of |
1466 | C<next::method>. |
1467 | |
1468 | sub new { |
1469 | my ( $class, $attrs ) = @_; |
1470 | |
1471 | $attrs->{foo} = 'bar' unless defined $attrs->{foo}; |
1472 | |
1473 | my $new = $class->next::method($attrs); |
1474 | |
1475 | return $new; |
1476 | } |
1477 | |
1478 | For more information about C<next::method>, look in the L<Class::C3> |
1479 | documentation. See also L<DBIx::Class::Manual::Component> for more |
1480 | ways to write your own base classes to do this. |
1481 | |
1482 | People looking for ways to do "triggers" with DBIx::Class are probably |
1483 | just looking for this. |
1484 | |
1485 | =head2 Changing one field whenever another changes |
086b93a2 |
1486 | |
1487 | For example, say that you have three columns, C<id>, C<number>, and |
1488 | C<squared>. You would like to make changes to C<number> and have |
1489 | C<squared> be automagically set to the value of C<number> squared. |
1490 | You can accomplish this by overriding C<store_column>: |
1491 | |
1492 | sub store_column { |
1493 | my ( $self, $name, $value ) = @_; |
1494 | if ($name eq 'number') { |
1495 | $self->squared($value * $value); |
1496 | } |
1497 | $self->next::method($name, $value); |
1498 | } |
1499 | |
1500 | Note that the hard work is done by the call to C<next::method>, which |
324572ca |
1501 | redispatches your call to store_column in the superclass(es). |
086b93a2 |
1502 | |
d2f3e87b |
1503 | =head2 Automatically creating related objects |
086b93a2 |
1504 | |
324572ca |
1505 | You might have a class C<Artist> which has many C<CD>s. Further, if you |
086b93a2 |
1506 | want to create a C<CD> object every time you insert an C<Artist> object. |
ccbebdbc |
1507 | You can accomplish this by overriding C<insert> on your objects: |
086b93a2 |
1508 | |
1509 | sub insert { |
ccbebdbc |
1510 | my ( $self, @args ) = @_; |
1511 | $self->next::method(@args); |
086b93a2 |
1512 | $self->cds->new({})->fill_from_artist($self)->insert; |
1513 | return $self; |
1514 | } |
1515 | |
1516 | where C<fill_from_artist> is a method you specify in C<CD> which sets |
1517 | values in C<CD> based on the data in the C<Artist> object you pass in. |
1518 | |
d2f3e87b |
1519 | =head2 Wrapping/overloading a column accessor |
1520 | |
1521 | B<Problem:> |
1522 | |
1523 | Say you have a table "Camera" and want to associate a description |
1524 | with each camera. For most cameras, you'll be able to generate the description from |
1525 | the other columns. However, in a few special cases you may want to associate a |
1526 | custom description with a camera. |
1527 | |
1528 | B<Solution:> |
1529 | |
1530 | In your database schema, define a description field in the "Camera" table that |
1531 | can contain text and null values. |
1532 | |
1533 | In DBIC, we'll overload the column accessor to provide a sane default if no |
1534 | custom description is defined. The accessor will either return or generate the |
1535 | description, depending on whether the field is null or not. |
1536 | |
1537 | First, in your "Camera" schema class, define the description field as follows: |
1538 | |
1539 | __PACKAGE__->add_columns(description => { accessor => '_description' }); |
1540 | |
1541 | Next, we'll define the accessor-wrapper subroutine: |
1542 | |
1543 | sub description { |
1544 | my $self = shift; |
1545 | |
1546 | # If there is an update to the column, we'll let the original accessor |
1547 | # deal with it. |
1548 | return $self->_description(@_) if @_; |
1549 | |
1550 | # Fetch the column value. |
1551 | my $description = $self->_description; |
1552 | |
1553 | # If there's something in the description field, then just return that. |
1554 | return $description if defined $description && length $descripton; |
1555 | |
1556 | # Otherwise, generate a description. |
1557 | return $self->generate_description; |
1558 | } |
1559 | |
1560 | =head1 DEBUGGING AND PROFILING |
1561 | |
1562 | =head2 DBIx::Class objects with Data::Dumper |
1def3451 |
1563 | |
1564 | L<Data::Dumper> can be a very useful tool for debugging, but sometimes it can |
1565 | be hard to find the pertinent data in all the data it can generate. |
1566 | Specifically, if one naively tries to use it like so, |
1567 | |
1568 | use Data::Dumper; |
1569 | |
1570 | my $cd = $schema->resultset('CD')->find(1); |
1571 | print Dumper($cd); |
1572 | |
1573 | several pages worth of data from the CD object's schema and result source will |
1574 | be dumped to the screen. Since usually one is only interested in a few column |
1575 | values of the object, this is not very helpful. |
1576 | |
1577 | Luckily, it is possible to modify the data before L<Data::Dumper> outputs |
1578 | it. Simply define a hook that L<Data::Dumper> will call on the object before |
1579 | dumping it. For example, |
1580 | |
1581 | package My::DB::CD; |
1582 | |
1583 | sub _dumper_hook { |
99fb1058 |
1584 | $_[0] = bless { |
1585 | %{ $_[0] }, |
1def3451 |
1586 | result_source => undef, |
99fb1058 |
1587 | }, ref($_[0]); |
1def3451 |
1588 | } |
1589 | |
1590 | [...] |
1591 | |
1592 | use Data::Dumper; |
1593 | |
22139027 |
1594 | local $Data::Dumper::Freezer = '_dumper_hook'; |
1def3451 |
1595 | |
1596 | my $cd = $schema->resultset('CD')->find(1); |
1597 | print Dumper($cd); |
1598 | # dumps $cd without its ResultSource |
1599 | |
1600 | If the structure of your schema is such that there is a common base class for |
1601 | all your table classes, simply put a method similar to C<_dumper_hook> in the |
1602 | base class and set C<$Data::Dumper::Freezer> to its name and L<Data::Dumper> |
1603 | will automagically clean up your data before printing it. See |
1604 | L<Data::Dumper/EXAMPLES> for more information. |
1605 | |
4c248161 |
1606 | =head2 Profiling |
1607 | |
85f78622 |
1608 | When you enable L<DBIx::Class::Storage>'s debugging it prints the SQL |
4c248161 |
1609 | executed as well as notifications of query completion and transaction |
1610 | begin/commit. If you'd like to profile the SQL you can subclass the |
1611 | L<DBIx::Class::Storage::Statistics> class and write your own profiling |
1612 | mechanism: |
1613 | |
1614 | package My::Profiler; |
1615 | use strict; |
1616 | |
1617 | use base 'DBIx::Class::Storage::Statistics'; |
1618 | |
1619 | use Time::HiRes qw(time); |
1620 | |
1621 | my $start; |
1622 | |
1623 | sub query_start { |
1624 | my $self = shift(); |
1625 | my $sql = shift(); |
1626 | my $params = @_; |
1627 | |
70f39278 |
1628 | $self->print("Executing $sql: ".join(', ', @params)."\n"); |
4c248161 |
1629 | $start = time(); |
1630 | } |
1631 | |
1632 | sub query_end { |
1633 | my $self = shift(); |
1634 | my $sql = shift(); |
1635 | my @params = @_; |
1636 | |
70f39278 |
1637 | my $elapsed = sprintf("%0.4f", time() - $start); |
1638 | $self->print("Execution took $elapsed seconds.\n"); |
4c248161 |
1639 | $start = undef; |
1640 | } |
1641 | |
1642 | 1; |
1643 | |
1644 | You can then install that class as the debugging object: |
1645 | |
70f39278 |
1646 | __PACKAGE__->storage->debugobj(new My::Profiler()); |
1647 | __PACKAGE__->storage->debug(1); |
4c248161 |
1648 | |
1649 | A more complicated example might involve storing each execution of SQL in an |
1650 | array: |
1651 | |
1652 | sub query_end { |
1653 | my $self = shift(); |
1654 | my $sql = shift(); |
1655 | my @params = @_; |
1656 | |
1657 | my $elapsed = time() - $start; |
1658 | push(@{ $calls{$sql} }, { |
1659 | params => \@params, |
1660 | elapsed => $elapsed |
1661 | }); |
1662 | } |
1663 | |
1664 | You could then create average, high and low execution times for an SQL |
1665 | statement and dig down to see if certain parameters cause aberrant behavior. |
70f39278 |
1666 | You might want to check out L<DBIx::Class::QueryLog> as well. |
4c248161 |
1667 | |
bc96f260 |
1668 | =head1 STARTUP SPEED |
1669 | |
1670 | L<DBIx::Class|DBIx::Class> programs can have a significant startup delay |
1671 | as the ORM loads all the relevant classes. This section examines |
1672 | techniques for reducing the startup delay. |
1673 | |
1674 | These tips are are listed in order of decreasing effectiveness - so the |
1675 | first tip, if applicable, should have the greatest effect on your |
1676 | application. |
1677 | |
1678 | =head2 Statically Define Your Schema |
1679 | |
1680 | If you are using |
1681 | L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to build the |
1682 | classes dynamically based on the database schema then there will be a |
1683 | significant startup delay. |
1684 | |
1685 | For production use a statically defined schema (which can be generated |
1686 | using L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to dump |
1687 | the database schema once - see |
1688 | L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> and |
1689 | L<dump_directory|DBIx::Class::Schema::Loader/dump_directory> for more |
1690 | details on creating static schemas from a database). |
1691 | |
1692 | =head2 Move Common Startup into a Base Class |
1693 | |
1694 | Typically L<DBIx::Class> result classes start off with |
1695 | |
1696 | use base qw/DBIx::Class/; |
1697 | __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/); |
1698 | |
1699 | If this preamble is moved into a common base class:- |
1700 | |
1701 | package MyDBICbase; |
1702 | |
1703 | use base qw/DBIx::Class/; |
1704 | __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/); |
1705 | 1; |
1706 | |
1707 | and each result class then uses this as a base:- |
1708 | |
1709 | use base qw/MyDBICbase/; |
1710 | |
1711 | then the load_components is only performed once, which can result in a |
1712 | considerable startup speedup for schemas with many classes. |
1713 | |
1714 | =head2 Explicitly List Schema Result Classes |
1715 | |
1716 | The schema class will normally contain |
1717 | |
1718 | __PACKAGE__->load_classes(); |
1719 | |
1720 | to load the result classes. This will use L<Module::Find|Module::Find> |
1721 | to find and load the appropriate modules. Explicitly defining the |
1722 | classes you wish to load will remove the overhead of |
1723 | L<Module::Find|Module::Find> and the related directory operations:- |
1724 | |
1725 | __PACKAGE__->load_classes(qw/ CD Artist Track /); |
1726 | |
1727 | If you are instead using the L<load_namespaces|DBIx::Class::Schema/load_namespaces> |
1728 | syntax to load the appropriate classes there is not a direct alternative |
1729 | avoiding L<Module::Find|Module::Find>. |
7aaec96c |
1730 | |
40dbc108 |
1731 | =cut |