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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 |
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10 | paged resultset, which will fetch only a defined number of records at a time: |
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11 | |
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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 | |
bade79c4 |
20 | return $rs->all(); # all records for page 1 |
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21 | |
b4664250 |
22 | return $rs->page(2); # records for page 2 |
23 | |
ec30560d |
24 | You can get a L<Data::Page> object for the resultset (suitable for use |
25 | in e.g. a template) using the C<pager> method: |
faf62551 |
26 | |
bade79c4 |
27 | return $rs->pager(); |
faf62551 |
28 | |
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29 | =head2 Complex WHERE clauses |
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30 | |
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31 | Sometimes you need to formulate a query using specific operators: |
32 | |
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33 | my @albums = $schema->resultset('Album')->search({ |
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34 | artist => { 'like', '%Lamb%' }, |
35 | title => { 'like', '%Fear of Fours%' }, |
36 | }); |
40dbc108 |
37 | |
38 | This results in something like the following C<WHERE> clause: |
39 | |
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40 | WHERE artist LIKE '%Lamb%' AND title LIKE '%Fear of Fours%' |
40dbc108 |
41 | |
42 | Other queries might require slightly more complex logic: |
43 | |
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44 | my @albums = $schema->resultset('Album')->search({ |
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45 | -or => [ |
46 | -and => [ |
47 | artist => { 'like', '%Smashing Pumpkins%' }, |
48 | title => 'Siamese Dream', |
49 | ], |
50 | artist => 'Starchildren', |
51 | ], |
52 | }); |
40dbc108 |
53 | |
54 | This results in the following C<WHERE> clause: |
55 | |
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56 | WHERE ( artist LIKE '%Smashing Pumpkins%' AND title = 'Siamese Dream' ) |
57 | OR artist = 'Starchildren' |
40dbc108 |
58 | |
59 | For more information on generating complex queries, see |
60 | L<SQL::Abstract/WHERE CLAUSES>. |
ee38fa40 |
61 | |
b9823354 |
62 | =head2 Retrieve one and only one row from a resultset |
63 | |
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64 | Sometimes you need only the first "top" row of a resultset. While this |
65 | can be easily done with L<< $rs->first|DBIx::Class::ResultSet/first |
66 | >>, it is suboptimal, as a full blown cursor for the resultset will be |
67 | created and then immediately destroyed after fetching the first row |
68 | object. L<< $rs->single|DBIx::Class::ResultSet/single >> is designed |
69 | specifically for this case - it will grab the first returned result |
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70 | without even instantiating a cursor. |
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71 | |
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72 | Before replacing all your calls to C<first()> with C<single()> please observe the |
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73 | following CAVEATS: |
74 | |
75 | =over |
76 | |
77 | =item * |
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78 | |
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79 | While single() takes a search condition just like search() does, it does |
80 | _not_ accept search attributes. However one can always chain a single() to |
81 | a search(): |
82 | |
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83 | my $top_cd = $cd_rs->search({}, { order_by => 'rating' })->single; |
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84 | |
85 | |
86 | =item * |
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87 | |
b9823354 |
88 | Since single() is the engine behind find(), it is designed to fetch a |
89 | single row per database query. Thus a warning will be issued when the |
90 | underlying SELECT returns more than one row. Sometimes however this usage |
91 | is valid: i.e. we have an arbitrary number of cd's but only one of them is |
92 | at the top of the charts at any given time. If you know what you are doing, |
93 | you can silence the warning by explicitly limiting the resultset size: |
94 | |
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95 | my $top_cd = $cd_rs->search ({}, { order_by => 'rating', rows => 1 })->single; |
b9823354 |
96 | |
97 | =back |
98 | |
d2f3e87b |
99 | =head2 Arbitrary SQL through a custom ResultSource |
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100 | |
101 | Sometimes you have to run arbitrary SQL because your query is too complex |
102 | (e.g. it contains Unions, Sub-Selects, Stored Procedures, etc.) or has to |
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103 | be optimized for your database in a special way, but you still want to |
104 | get the results as a L<DBIx::Class::ResultSet>. |
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105 | |
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106 | This is accomplished by defining a |
107 | L<ResultSource::View|DBIx::Class::ResultSource::View> for your query, |
108 | almost like you would define a regular ResultSource. |
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109 | |
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110 | package My::Schema::Result::UserFriendsComplex; |
111 | use strict; |
112 | use warnings; |
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113 | use base qw/DBIx::Class/; |
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114 | |
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115 | __PACKAGE__->load_components('Core'); |
116 | __PACKAGE__->table_class('DBIx::Class::ResultSource::View'); |
117 | |
118 | # ->table, ->add_columns, etc. |
119 | |
7adc2091 |
120 | # do not attempt to deploy() this view |
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121 | __PACKAGE__->result_source_instance->is_virtual(1); |
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122 | |
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123 | __PACKAGE__->result_source_instance->view_definition(q[ |
124 | SELECT u.* FROM user u |
125 | INNER JOIN user_friends f ON u.id = f.user_id |
126 | WHERE f.friend_user_id = ? |
127 | UNION |
128 | SELECT u.* FROM user u |
129 | INNER JOIN user_friends f ON u.id = f.friend_user_id |
130 | WHERE f.user_id = ? |
131 | ]); |
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132 | |
133 | Next, you can execute your complex query using bind parameters like this: |
134 | |
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135 | my $friends = $schema->resultset( 'UserFriendsComplex' )->search( {}, |
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136 | { |
137 | bind => [ 12345, 12345 ] |
138 | } |
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139 | ); |
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140 | |
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141 | ... and you'll get back a perfect L<DBIx::Class::ResultSet> (except, of course, |
142 | that you cannot modify the rows it contains, ie. cannot call L</update>, |
143 | L</delete>, ... on it). |
144 | |
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145 | Note that you cannot have bind parameters unless is_virtual is set to true. |
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146 | |
7adc2091 |
147 | =over |
148 | |
149 | =item * NOTE |
150 | |
151 | If you're using the old deprecated C<< $rsrc_instance->name(\'( SELECT ...') >> |
152 | method for custom SQL execution, you are highly encouraged to update your code |
153 | to use a virtual view as above. If you do not want to change your code, and just |
154 | want to suppress the deprecation warning when you call |
155 | L<DBIx::Class::Schema/deploy>, add this line to your source definition, so that |
156 | C<deploy> will exclude this "table": |
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157 | |
158 | sub sqlt_deploy_hook { $_[1]->schema->drop_table ($_[1]) } |
159 | |
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160 | =back |
161 | |
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162 | =head2 Using specific columns |
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163 | |
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164 | When you only want specific columns from a table, you can use |
165 | C<columns> to specify which ones you need. This is useful to avoid |
166 | loading columns with large amounts of data that you aren't about to |
167 | use anyway: |
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168 | |
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169 | my $rs = $schema->resultset('Artist')->search( |
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170 | undef, |
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171 | { |
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172 | columns => [qw/ name /] |
bade79c4 |
173 | } |
174 | ); |
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175 | |
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176 | # Equivalent SQL: |
177 | # SELECT artist.name FROM artist |
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178 | |
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179 | This is a shortcut for C<select> and C<as>, see below. C<columns> |
180 | cannot be used together with C<select> and C<as>. |
181 | |
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182 | =head2 Using database functions or stored procedures |
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183 | |
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184 | The combination of C<select> and C<as> can be used to return the result of a |
185 | database function or stored procedure as a column value. You use C<select> to |
186 | specify the source for your column value (e.g. a column name, function, or |
187 | stored procedure name). You then use C<as> to set the column name you will use |
188 | to access the returned value: |
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189 | |
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190 | my $rs = $schema->resultset('Artist')->search( |
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191 | {}, |
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192 | { |
193 | select => [ 'name', { LENGTH => 'name' } ], |
194 | as => [qw/ name name_length /], |
195 | } |
196 | ); |
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197 | |
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198 | # Equivalent SQL: |
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199 | # SELECT name name, LENGTH( name ) |
bade79c4 |
200 | # FROM artist |
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201 | |
324bc214 |
202 | Note that the C<as> attribute B<has absolutely nothing to do> with the sql |
203 | syntax C< SELECT foo AS bar > (see the documentation in |
204 | L<DBIx::Class::ResultSet/ATTRIBUTES>). You can control the C<AS> part of the |
205 | generated SQL via the C<-as> field attribute as follows: |
206 | |
207 | my $rs = $schema->resultset('Artist')->search( |
208 | {}, |
209 | { |
210 | join => 'cds', |
211 | distinct => 1, |
212 | +select => [ { count => 'cds.cdid', -as => 'amount_of_cds' } ], |
213 | +as => [qw/num_cds/], |
214 | order_by => { -desc => 'amount_of_cds' }, |
215 | } |
216 | ); |
217 | |
218 | # Equivalent SQL |
219 | # SELECT me.artistid, me.name, me.rank, me.charfield, COUNT( cds.cdid ) AS amount_of_cds |
220 | # FROM artist me LEFT JOIN cd cds ON cds.artist = me.artistid |
221 | # GROUP BY me.artistid, me.name, me.rank, me.charfield |
222 | # ORDER BY amount_of_cds DESC |
223 | |
224 | |
225 | If your alias exists as a column in your base class (i.e. it was added with |
226 | L<add_columns|DBIx::Class::ResultSource/add_columns>), you just access it as |
227 | normal. Our C<Artist> class has a C<name> column, so we just use the C<name> |
228 | accessor: |
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229 | |
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230 | my $artist = $rs->first(); |
231 | my $name = $artist->name(); |
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232 | |
233 | If on the other hand the alias does not correspond to an existing column, you |
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234 | have to fetch the value using the C<get_column> accessor: |
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235 | |
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236 | my $name_length = $artist->get_column('name_length'); |
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237 | |
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238 | If you don't like using C<get_column>, you can always create an accessor for |
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239 | any of your aliases using either of these: |
240 | |
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241 | # Define accessor manually: |
242 | sub name_length { shift->get_column('name_length'); } |
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243 | |
bade79c4 |
244 | # Or use DBIx::Class::AccessorGroup: |
245 | __PACKAGE__->mk_group_accessors('column' => 'name_length'); |
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246 | |
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247 | =head2 SELECT DISTINCT with multiple columns |
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248 | |
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249 | my $rs = $schema->resultset('Artist')->search( |
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250 | {}, |
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251 | { |
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252 | columns => [ qw/artist_id name rank/ ], |
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253 | distinct => 1 |
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254 | } |
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255 | ); |
256 | |
257 | my $rs = $schema->resultset('Artist')->search( |
258 | {}, |
259 | { |
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260 | columns => [ qw/artist_id name rank/ ], |
261 | group_by => [ qw/artist_id name rank/ ], |
bade79c4 |
262 | } |
263 | ); |
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264 | |
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265 | # Equivalent SQL: |
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266 | # SELECT me.artist_id, me.name, me.rank |
58a20107 |
267 | # FROM artist me |
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268 | # GROUP BY artist_id, name, rank |
58a20107 |
269 | |
d2f3e87b |
270 | =head2 SELECT COUNT(DISTINCT colname) |
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271 | |
58a20107 |
272 | my $rs = $schema->resultset('Artist')->search( |
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273 | {}, |
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274 | { |
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275 | columns => [ qw/name/ ], |
276 | distinct => 1 |
bade79c4 |
277 | } |
278 | ); |
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279 | |
58a20107 |
280 | my $rs = $schema->resultset('Artist')->search( |
281 | {}, |
282 | { |
283 | columns => [ qw/name/ ], |
284 | group_by => [ qw/name/ ], |
285 | } |
286 | ); |
287 | |
288 | my $count = $rs->count; |
289 | |
290 | # Equivalent SQL: |
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291 | # SELECT COUNT( * ) FROM (SELECT me.name FROM artist me GROUP BY me.name) count_subq: |
3d565896 |
292 | |
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293 | =head2 Grouping results |
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294 | |
295 | L<DBIx::Class> supports C<GROUP BY> as follows: |
296 | |
297 | my $rs = $schema->resultset('Artist')->search( |
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298 | {}, |
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299 | { |
300 | join => [qw/ cds /], |
51458a6a |
301 | select => [ 'name', { count => 'cds.id' } ], |
bade79c4 |
302 | as => [qw/ name cd_count /], |
303 | group_by => [qw/ name /] |
304 | } |
305 | ); |
6607ee1b |
306 | |
bade79c4 |
307 | # Equivalent SQL: |
51458a6a |
308 | # SELECT name, COUNT( cd.id ) FROM artist |
309 | # LEFT JOIN cd ON artist.id = cd.artist |
bade79c4 |
310 | # GROUP BY name |
6607ee1b |
311 | |
d676881f |
312 | Please see L<DBIx::Class::ResultSet/ATTRIBUTES> documentation if you |
313 | are in any way unsure about the use of the attributes above (C< join |
314 | >, C< select >, C< as > and C< group_by >). |
315 | |
70bb942d |
316 | =head2 Subqueries (EXPERIMENTAL) |
03834f77 |
317 | |
318 | You can write subqueries relatively easily in DBIC. |
319 | |
320 | my $inside_rs = $schema->resultset('Artist')->search({ |
321 | name => [ 'Billy Joel', 'Brittany Spears' ], |
322 | }); |
323 | |
68a797c1 |
324 | my $rs = $schema->resultset('CD')->search({ |
03834f77 |
325 | artist_id => { 'IN' => $inside_rs->get_column('id')->as_query }, |
326 | }); |
327 | |
328 | The usual operators ( =, !=, IN, NOT IN, etc) are supported. |
329 | |
330 | B<NOTE>: You have to explicitly use '=' when doing an equality comparison. |
331 | The following will B<not> work: |
332 | |
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333 | my $rs = $schema->resultset('CD')->search({ |
03834f77 |
334 | artist_id => $inside_rs->get_column('id')->as_query, |
335 | }); |
336 | |
0a62f675 |
337 | =head3 Support |
338 | |
339 | Subqueries are supported in the where clause (first hashref), and in the |
340 | from, select, and +select attributes. |
341 | |
68a797c1 |
342 | =head3 Correlated subqueries |
343 | |
344 | my $cdrs = $schema->resultset('CD'); |
345 | my $rs = $cdrs->search({ |
346 | year => { |
347 | '=' => $cdrs->search( |
cd87b928 |
348 | { artist_id => { '=' => \'me.artist_id' } }, |
68a797c1 |
349 | { alias => 'inner' } |
350 | )->get_column('year')->max_rs->as_query, |
351 | }, |
352 | }); |
353 | |
354 | That creates the following SQL: |
355 | |
356 | SELECT me.cdid, me.artist, me.title, me.year, me.genreid, me.single_track |
357 | FROM cd me |
358 | WHERE year = ( |
359 | SELECT MAX(inner.year) |
360 | FROM cd inner |
cd87b928 |
361 | WHERE artist_id = me.artist_id |
68a797c1 |
362 | ) |
363 | |
6a9530d1 |
364 | =head3 EXPERIMENTAL |
365 | |
366 | Please note that subqueries are considered an experimental feature. |
367 | |
d2f3e87b |
368 | =head2 Predefined searches |
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369 | |
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370 | You can write your own L<DBIx::Class::ResultSet> class by inheriting from it |
0132e136 |
371 | and defining often used searches as methods: |
74dc2edc |
372 | |
373 | package My::DBIC::ResultSet::CD; |
374 | use strict; |
375 | use warnings; |
376 | use base 'DBIx::Class::ResultSet'; |
377 | |
378 | sub search_cds_ordered { |
379 | my ($self) = @_; |
380 | |
381 | return $self->search( |
382 | {}, |
383 | { order_by => 'name DESC' }, |
384 | ); |
385 | } |
386 | |
387 | 1; |
388 | |
389 | To use your resultset, first tell DBIx::Class to create an instance of it |
390 | for you, in your My::DBIC::Schema::CD class: |
391 | |
9dc1bfce |
392 | # class definition as normal |
393 | __PACKAGE__->load_components(qw/ Core /); |
394 | __PACKAGE__->table('cd'); |
395 | |
396 | # tell DBIC to use the custom ResultSet class |
74dc2edc |
397 | __PACKAGE__->resultset_class('My::DBIC::ResultSet::CD'); |
398 | |
9dc1bfce |
399 | Note that C<resultset_class> must be called after C<load_components> and C<table>, or you will get errors about missing methods. |
400 | |
74dc2edc |
401 | Then call your new method in your code: |
402 | |
403 | my $ordered_cds = $schema->resultset('CD')->search_cds_ordered(); |
404 | |
d2f3e87b |
405 | =head2 Using SQL functions on the left hand side of a comparison |
1c133e22 |
406 | |
407 | Using SQL functions on the left hand side of a comparison is generally |
408 | not a good idea since it requires a scan of the entire table. However, |
409 | it can be accomplished with C<DBIx::Class> when necessary. |
410 | |
411 | If you do not have quoting on, simply include the function in your search |
412 | specification as you would any column: |
413 | |
414 | $rs->search({ 'YEAR(date_of_birth)' => 1979 }); |
415 | |
416 | With quoting on, or for a more portable solution, use the C<where> |
417 | attribute: |
418 | |
419 | $rs->search({}, { where => \'YEAR(date_of_birth) = 1979' }); |
420 | |
421 | =begin hidden |
422 | |
423 | (When the bind args ordering bug is fixed, this technique will be better |
424 | and can replace the one above.) |
425 | |
426 | With quoting on, or for a more portable solution, use the C<where> and |
427 | C<bind> attributes: |
428 | |
429 | $rs->search({}, { |
430 | where => \'YEAR(date_of_birth) = ?', |
431 | bind => [ 1979 ] |
432 | }); |
433 | |
434 | =end hidden |
435 | |
d2f3e87b |
436 | =head1 JOINS AND PREFETCHING |
437 | |
87980de7 |
438 | =head2 Using joins and prefetch |
439 | |
bade79c4 |
440 | You can use the C<join> attribute to allow searching on, or sorting your |
cd87b928 |
441 | results by, one or more columns in a related table. |
442 | |
443 | This requires that you have defined the L<DBIx::Class::Relationship>. For example : |
444 | |
445 | My::Schema::CD->has_many( artists => 'My::Schema::Artist', 'artist_id'); |
446 | |
447 | To return all CDs matching a particular artist name, you specify the name of the relationship ('artists'): |
ea6309e2 |
448 | |
bade79c4 |
449 | my $rs = $schema->resultset('CD')->search( |
450 | { |
0132e136 |
451 | 'artists.name' => 'Bob Marley' |
bade79c4 |
452 | }, |
453 | { |
cd87b928 |
454 | join => 'artists', # join the artist table |
bade79c4 |
455 | } |
456 | ); |
457 | |
458 | # Equivalent SQL: |
459 | # SELECT cd.* FROM cd |
460 | # JOIN artist ON cd.artist = artist.id |
461 | # WHERE artist.name = 'Bob Marley' |
462 | |
cd87b928 |
463 | In that example both the join, and the condition use the relationship name rather than the table name |
0132e136 |
464 | (see L<DBIx::Class::Manual::Joining> for more details on aliasing ). |
cd87b928 |
465 | |
bade79c4 |
466 | If required, you can now sort on any column in the related tables by including |
cd87b928 |
467 | it in your C<order_by> attribute, (again using the aliased relation name rather than table name) : |
bade79c4 |
468 | |
469 | my $rs = $schema->resultset('CD')->search( |
470 | { |
cd87b928 |
471 | 'artists.name' => 'Bob Marley' |
bade79c4 |
472 | }, |
473 | { |
cd87b928 |
474 | join => 'artists', |
475 | order_by => [qw/ artists.name /] |
bade79c4 |
476 | } |
2f81ed0f |
477 | ); |
ea6309e2 |
478 | |
bade79c4 |
479 | # Equivalent SQL: |
480 | # SELECT cd.* FROM cd |
481 | # JOIN artist ON cd.artist = artist.id |
482 | # WHERE artist.name = 'Bob Marley' |
483 | # ORDER BY artist.name |
ea6309e2 |
484 | |
bade79c4 |
485 | Note that the C<join> attribute should only be used when you need to search or |
486 | sort using columns in a related table. Joining related tables when you only |
487 | need columns from the main table will make performance worse! |
ea6309e2 |
488 | |
bade79c4 |
489 | Now let's say you want to display a list of CDs, each with the name of the |
490 | artist. The following will work fine: |
ea6309e2 |
491 | |
bade79c4 |
492 | while (my $cd = $rs->next) { |
493 | print "CD: " . $cd->title . ", Artist: " . $cd->artist->name; |
494 | } |
ea6309e2 |
495 | |
bade79c4 |
496 | There is a problem however. We have searched both the C<cd> and C<artist> tables |
497 | in our main query, but we have only returned data from the C<cd> table. To get |
498 | the artist name for any of the CD objects returned, L<DBIx::Class> will go back |
499 | to the database: |
ea6309e2 |
500 | |
bade79c4 |
501 | SELECT artist.* FROM artist WHERE artist.id = ? |
ea6309e2 |
502 | |
503 | A statement like the one above will run for each and every CD returned by our |
504 | main query. Five CDs, five extra queries. A hundred CDs, one hundred extra |
505 | queries! |
506 | |
bade79c4 |
507 | Thankfully, L<DBIx::Class> has a C<prefetch> attribute to solve this problem. |
897342e4 |
508 | This allows you to fetch results from related tables in advance: |
ea6309e2 |
509 | |
bade79c4 |
510 | my $rs = $schema->resultset('CD')->search( |
511 | { |
cd87b928 |
512 | 'artists.name' => 'Bob Marley' |
bade79c4 |
513 | }, |
514 | { |
cd87b928 |
515 | join => 'artists', |
516 | order_by => [qw/ artists.name /], |
517 | prefetch => 'artists' # return artist data too! |
bade79c4 |
518 | } |
519 | ); |
ea6309e2 |
520 | |
bade79c4 |
521 | # Equivalent SQL (note SELECT from both "cd" and "artist"): |
522 | # SELECT cd.*, artist.* FROM cd |
523 | # JOIN artist ON cd.artist = artist.id |
524 | # WHERE artist.name = 'Bob Marley' |
525 | # ORDER BY artist.name |
ea6309e2 |
526 | |
527 | The code to print the CD list remains the same: |
528 | |
bade79c4 |
529 | while (my $cd = $rs->next) { |
530 | print "CD: " . $cd->title . ", Artist: " . $cd->artist->name; |
531 | } |
ea6309e2 |
532 | |
bade79c4 |
533 | L<DBIx::Class> has now prefetched all matching data from the C<artist> table, |
ea6309e2 |
534 | so no additional SQL statements are executed. You now have a much more |
535 | efficient query. |
536 | |
bade79c4 |
537 | Also note that C<prefetch> should only be used when you know you will |
ea6309e2 |
538 | definitely use data from a related table. Pre-fetching related tables when you |
539 | only need columns from the main table will make performance worse! |
540 | |
51458a6a |
541 | =head2 Multiple joins |
542 | |
543 | In the examples above, the C<join> attribute was a scalar. If you |
544 | pass an array reference instead, you can join to multiple tables. In |
545 | this example, we want to limit the search further, using |
546 | C<LinerNotes>: |
547 | |
548 | # Relationships defined elsewhere: |
549 | # CD->belongs_to('artist' => 'Artist'); |
550 | # CD->has_one('liner_notes' => 'LinerNotes', 'cd'); |
551 | my $rs = $schema->resultset('CD')->search( |
552 | { |
553 | 'artist.name' => 'Bob Marley' |
554 | 'liner_notes.notes' => { 'like', '%some text%' }, |
555 | }, |
556 | { |
557 | join => [qw/ artist liner_notes /], |
558 | order_by => [qw/ artist.name /], |
559 | } |
560 | ); |
561 | |
562 | # Equivalent SQL: |
563 | # SELECT cd.*, artist.*, liner_notes.* FROM cd |
564 | # JOIN artist ON cd.artist = artist.id |
565 | # JOIN liner_notes ON cd.id = liner_notes.cd |
566 | # WHERE artist.name = 'Bob Marley' |
567 | # ORDER BY artist.name |
568 | |
d2f3e87b |
569 | =head2 Multi-step joins |
ea6309e2 |
570 | |
571 | Sometimes you want to join more than one relationship deep. In this example, |
bade79c4 |
572 | we want to find all C<Artist> objects who have C<CD>s whose C<LinerNotes> |
573 | contain a specific string: |
574 | |
575 | # Relationships defined elsewhere: |
576 | # Artist->has_many('cds' => 'CD', 'artist'); |
577 | # CD->has_one('liner_notes' => 'LinerNotes', 'cd'); |
578 | |
579 | my $rs = $schema->resultset('Artist')->search( |
580 | { |
581 | 'liner_notes.notes' => { 'like', '%some text%' }, |
582 | }, |
583 | { |
584 | join => { |
585 | 'cds' => 'liner_notes' |
586 | } |
587 | } |
588 | ); |
ea6309e2 |
589 | |
bade79c4 |
590 | # Equivalent SQL: |
591 | # SELECT artist.* FROM artist |
51458a6a |
592 | # LEFT JOIN cd ON artist.id = cd.artist |
593 | # LEFT JOIN liner_notes ON cd.id = liner_notes.cd |
bade79c4 |
594 | # WHERE liner_notes.notes LIKE '%some text%' |
ea6309e2 |
595 | |
596 | Joins can be nested to an arbitrary level. So if we decide later that we |
597 | want to reduce the number of Artists returned based on who wrote the liner |
598 | notes: |
599 | |
bade79c4 |
600 | # Relationship defined elsewhere: |
601 | # LinerNotes->belongs_to('author' => 'Person'); |
602 | |
603 | my $rs = $schema->resultset('Artist')->search( |
604 | { |
605 | 'liner_notes.notes' => { 'like', '%some text%' }, |
606 | 'author.name' => 'A. Writer' |
607 | }, |
608 | { |
609 | join => { |
610 | 'cds' => { |
611 | 'liner_notes' => 'author' |
ea6309e2 |
612 | } |
bade79c4 |
613 | } |
614 | } |
615 | ); |
ea6309e2 |
616 | |
bade79c4 |
617 | # Equivalent SQL: |
618 | # SELECT artist.* FROM artist |
51458a6a |
619 | # LEFT JOIN cd ON artist.id = cd.artist |
620 | # LEFT JOIN liner_notes ON cd.id = liner_notes.cd |
621 | # LEFT JOIN author ON author.id = liner_notes.author |
bade79c4 |
622 | # WHERE liner_notes.notes LIKE '%some text%' |
623 | # AND author.name = 'A. Writer' |
87980de7 |
624 | |
51458a6a |
625 | =head2 Multi-step and multiple joins |
626 | |
627 | With various combinations of array and hash references, you can join |
628 | tables in any combination you desire. For example, to join Artist to |
629 | CD and Concert, and join CD to LinerNotes: |
630 | |
631 | # Relationships defined elsewhere: |
632 | # Artist->has_many('concerts' => 'Concert', 'artist'); |
633 | |
634 | my $rs = $schema->resultset('Artist')->search( |
635 | { }, |
636 | { |
637 | join => [ |
638 | { |
639 | cds => 'liner_notes' |
640 | }, |
641 | 'concerts' |
642 | ], |
643 | } |
644 | ); |
645 | |
646 | # Equivalent SQL: |
647 | # SELECT artist.* FROM artist |
648 | # LEFT JOIN cd ON artist.id = cd.artist |
649 | # LEFT JOIN liner_notes ON cd.id = liner_notes.cd |
650 | # LEFT JOIN concert ON artist.id = concert.artist |
651 | |
897342e4 |
652 | =head2 Multi-step prefetch |
653 | |
d76788de |
654 | C<prefetch> can be nested more than one relationship |
897342e4 |
655 | deep using the same syntax as a multi-step join: |
656 | |
657 | my $rs = $schema->resultset('Tag')->search( |
ac2803ef |
658 | {}, |
897342e4 |
659 | { |
660 | prefetch => { |
661 | cd => 'artist' |
662 | } |
663 | } |
664 | ); |
665 | |
666 | # Equivalent SQL: |
667 | # SELECT tag.*, cd.*, artist.* FROM tag |
51458a6a |
668 | # JOIN cd ON tag.cd = cd.id |
669 | # JOIN artist ON cd.artist = artist.id |
897342e4 |
670 | |
671 | Now accessing our C<cd> and C<artist> relationships does not need additional |
672 | SQL statements: |
673 | |
674 | my $tag = $rs->first; |
675 | print $tag->cd->artist->name; |
676 | |
d2f3e87b |
677 | =head1 ROW-LEVEL OPERATIONS |
678 | |
679 | =head2 Retrieving a row object's Schema |
680 | |
681 | It is possible to get a Schema object from a row object like so: |
682 | |
683 | my $schema = $cd->result_source->schema; |
684 | # use the schema as normal: |
0132e136 |
685 | my $artist_rs = $schema->resultset('Artist'); |
d2f3e87b |
686 | |
687 | This can be useful when you don't want to pass around a Schema object to every |
688 | method. |
689 | |
690 | =head2 Getting the value of the primary key for the last database insert |
691 | |
692 | AKA getting last_insert_id |
693 | |
d76788de |
694 | Thanks to the core component PK::Auto, this is straightforward: |
d2f3e87b |
695 | |
696 | my $foo = $rs->create(\%blah); |
697 | # do more stuff |
698 | my $id = $foo->id; # foo->my_primary_key_field will also work. |
699 | |
700 | If you are not using autoincrementing primary keys, this will probably |
701 | not work, but then you already know the value of the last primary key anyway. |
702 | |
703 | =head2 Stringification |
704 | |
0132e136 |
705 | Employ the standard stringification technique by using the L<overload> |
d2f3e87b |
706 | module. |
707 | |
708 | To make an object stringify itself as a single column, use something |
b24d86a1 |
709 | like this (replace C<name> with the column/method of your choice): |
d2f3e87b |
710 | |
711 | use overload '""' => sub { shift->name}, fallback => 1; |
712 | |
713 | For more complex stringification, you can use an anonymous subroutine: |
714 | |
715 | use overload '""' => sub { $_[0]->name . ", " . |
716 | $_[0]->address }, fallback => 1; |
717 | |
718 | =head3 Stringification Example |
719 | |
720 | Suppose we have two tables: C<Product> and C<Category>. The table |
721 | specifications are: |
722 | |
723 | Product(id, Description, category) |
724 | Category(id, Description) |
725 | |
726 | C<category> is a foreign key into the Category table. |
727 | |
728 | If you have a Product object C<$obj> and write something like |
729 | |
730 | print $obj->category |
731 | |
732 | things will not work as expected. |
733 | |
734 | To obtain, for example, the category description, you should add this |
735 | method to the class defining the Category table: |
736 | |
737 | use overload "" => sub { |
738 | my $self = shift; |
739 | |
740 | return $self->Description; |
741 | }, fallback => 1; |
742 | |
743 | =head2 Want to know if find_or_create found or created a row? |
744 | |
745 | Just use C<find_or_new> instead, then check C<in_storage>: |
746 | |
747 | my $obj = $rs->find_or_new({ blah => 'blarg' }); |
748 | unless ($obj->in_storage) { |
749 | $obj->insert; |
750 | # do whatever else you wanted if it was a new row |
751 | } |
752 | |
0132e136 |
753 | =head2 Static sub-classing DBIx::Class result classes |
6fc80947 |
754 | |
755 | AKA adding additional relationships/methods/etc. to a model for a |
756 | specific usage of the (shared) model. |
757 | |
0132e136 |
758 | B<Schema definition> |
759 | |
760 | package My::App::Schema; |
761 | |
762 | use base DBIx::Class::Schema; |
6fc80947 |
763 | |
764 | # load subclassed classes from My::App::Schema::Result/ResultSet |
765 | __PACKAGE__->load_namespaces; |
766 | |
767 | # load classes from shared model |
768 | load_classes({ |
769 | 'My::Shared::Model::Result' => [qw/ |
770 | Foo |
771 | Bar |
772 | /]}); |
773 | |
774 | 1; |
0132e136 |
775 | |
776 | B<Result-Subclass definition> |
777 | |
6fc80947 |
778 | package My::App::Schema::Result::Baz; |
0132e136 |
779 | |
780 | use strict; |
781 | use warnings; |
782 | use base My::Shared::Model::Result::Baz; |
783 | |
6fc80947 |
784 | # WARNING: Make sure you call table() again in your subclass, |
785 | # otherwise DBIx::Class::ResultSourceProxy::Table will not be called |
786 | # and the class name is not correctly registered as a source |
0132e136 |
787 | __PACKAGE__->table('baz'); |
788 | |
789 | sub additional_method { |
790 | return "I'm an additional method only needed by this app"; |
6fc80947 |
791 | } |
792 | |
793 | 1; |
0132e136 |
794 | |
795 | =head2 Dynamic Sub-classing DBIx::Class proxy classes |
d2f3e87b |
796 | |
797 | AKA multi-class object inflation from one table |
0132e136 |
798 | |
d2f3e87b |
799 | L<DBIx::Class> classes are proxy classes, therefore some different |
800 | techniques need to be employed for more than basic subclassing. In |
801 | this example we have a single user table that carries a boolean bit |
802 | for admin. We would like like to give the admin users |
0132e136 |
803 | objects (L<DBIx::Class::Row>) the same methods as a regular user but |
d2f3e87b |
804 | also special admin only methods. It doesn't make sense to create two |
805 | seperate proxy-class files for this. We would be copying all the user |
806 | methods into the Admin class. There is a cleaner way to accomplish |
807 | this. |
808 | |
809 | Overriding the C<inflate_result> method within the User proxy-class |
810 | gives us the effect we want. This method is called by |
811 | L<DBIx::Class::ResultSet> when inflating a result from storage. So we |
812 | grab the object being returned, inspect the values we are looking for, |
813 | bless it if it's an admin object, and then return it. See the example |
814 | below: |
0132e136 |
815 | |
816 | B<Schema Definition> |
817 | |
818 | package My::Schema; |
819 | |
820 | use base qw/DBIx::Class::Schema/; |
821 | |
6fc80947 |
822 | __PACKAGE__->load_namespaces; |
823 | |
824 | 1; |
0132e136 |
825 | |
826 | |
827 | B<Proxy-Class definitions> |
828 | |
829 | package My::Schema::Result::User; |
830 | |
831 | use strict; |
832 | use warnings; |
833 | use base qw/DBIx::Class/; |
834 | |
835 | ### Define what our admin class is, for ensure_class_loaded() |
836 | my $admin_class = __PACKAGE__ . '::Admin'; |
837 | |
838 | __PACKAGE__->load_components(qw/Core/); |
839 | |
840 | __PACKAGE__->table('users'); |
841 | |
842 | __PACKAGE__->add_columns(qw/user_id email password |
843 | firstname lastname active |
844 | admin/); |
845 | |
846 | __PACKAGE__->set_primary_key('user_id'); |
847 | |
848 | sub inflate_result { |
849 | my $self = shift; |
850 | my $ret = $self->next::method(@_); |
851 | if( $ret->admin ) {### If this is an admin, rebless for extra functions |
852 | $self->ensure_class_loaded( $admin_class ); |
853 | bless $ret, $admin_class; |
854 | } |
855 | return $ret; |
856 | } |
857 | |
858 | sub hello { |
859 | print "I am a regular user.\n"; |
860 | return ; |
861 | } |
862 | |
6fc80947 |
863 | 1; |
864 | |
0132e136 |
865 | |
866 | package My::Schema::Result::User::Admin; |
867 | |
868 | use strict; |
869 | use warnings; |
870 | use base qw/My::Schema::Result::User/; |
04d29efe |
871 | |
872 | # This line is important |
873 | __PACKAGE__->table('users'); |
0132e136 |
874 | |
875 | sub hello |
876 | { |
877 | print "I am an admin.\n"; |
878 | return; |
879 | } |
880 | |
881 | sub do_admin_stuff |
882 | { |
883 | print "I am doing admin stuff\n"; |
884 | return ; |
6fc80947 |
885 | } |
886 | |
887 | 1; |
0132e136 |
888 | |
889 | B<Test File> test.pl |
890 | |
891 | use warnings; |
892 | use strict; |
893 | use My::Schema; |
894 | |
895 | my $user_data = { email => 'someguy@place.com', |
896 | password => 'pass1', |
897 | admin => 0 }; |
898 | |
899 | my $admin_data = { email => 'someadmin@adminplace.com', |
900 | password => 'pass2', |
901 | admin => 1 }; |
902 | |
903 | my $schema = My::Schema->connection('dbi:Pg:dbname=test'); |
904 | |
905 | $schema->resultset('User')->create( $user_data ); |
906 | $schema->resultset('User')->create( $admin_data ); |
907 | |
908 | ### Now we search for them |
909 | my $user = $schema->resultset('User')->single( $user_data ); |
910 | my $admin = $schema->resultset('User')->single( $admin_data ); |
911 | |
912 | print ref $user, "\n"; |
913 | print ref $admin, "\n"; |
914 | |
915 | print $user->password , "\n"; # pass1 |
916 | print $admin->password , "\n";# pass2; inherited from User |
917 | print $user->hello , "\n";# I am a regular user. |
918 | print $admin->hello, "\n";# I am an admin. |
919 | |
920 | ### The statement below will NOT print |
921 | print "I can do admin stuff\n" if $user->can('do_admin_stuff'); |
922 | ### The statement below will print |
923 | print "I can do admin stuff\n" if $admin->can('do_admin_stuff'); |
d2f3e87b |
924 | |
a5b29361 |
925 | =head2 Skip row object creation for faster results |
d2f3e87b |
926 | |
927 | DBIx::Class is not built for speed, it's built for convenience and |
928 | ease of use, but sometimes you just need to get the data, and skip the |
929 | fancy objects. |
0132e136 |
930 | |
d2f3e87b |
931 | To do this simply use L<DBIx::Class::ResultClass::HashRefInflator>. |
0132e136 |
932 | |
d2f3e87b |
933 | my $rs = $schema->resultset('CD'); |
0132e136 |
934 | |
d2f3e87b |
935 | $rs->result_class('DBIx::Class::ResultClass::HashRefInflator'); |
0132e136 |
936 | |
d2f3e87b |
937 | my $hash_ref = $rs->find(1); |
a5b29361 |
938 | |
d2f3e87b |
939 | Wasn't that easy? |
bc96f260 |
940 | |
db2b2eb6 |
941 | Beware, changing the Result class using |
942 | L<DBIx::Class::ResultSet/result_class> will replace any existing class |
943 | completely including any special components loaded using |
944 | load_components, eg L<DBIx::Class::InflateColumn::DateTime>. |
945 | |
d2f3e87b |
946 | =head2 Get raw data for blindingly fast results |
947 | |
948 | If the L<HashRefInflator|DBIx::Class::ResultClass::HashRefInflator> solution |
949 | above is not fast enough for you, you can use a DBIx::Class to return values |
db2b2eb6 |
950 | exactly as they come out of the database with none of the convenience methods |
d2f3e87b |
951 | wrapped round them. |
952 | |
2d7d8459 |
953 | This is used like so: |
d2f3e87b |
954 | |
955 | my $cursor = $rs->cursor |
956 | while (my @vals = $cursor->next) { |
957 | # use $val[0..n] here |
958 | } |
959 | |
960 | You will need to map the array offsets to particular columns (you can |
db2b2eb6 |
961 | use the L<DBIx::Class::ResultSet/select> attribute of L<DBIx::Class::ResultSet/search> to force ordering). |
d2f3e87b |
962 | |
963 | =head1 RESULTSET OPERATIONS |
964 | |
965 | =head2 Getting Schema from a ResultSet |
966 | |
db2b2eb6 |
967 | To get the L<DBIx::Class::Schema> object from a ResultSet, do the following: |
d2f3e87b |
968 | |
969 | $rs->result_source->schema |
970 | |
971 | =head2 Getting Columns Of Data |
972 | |
973 | AKA Aggregating Data |
ac2803ef |
974 | |
975 | If you want to find the sum of a particular column there are several |
976 | ways, the obvious one is to use search: |
977 | |
978 | my $rs = $schema->resultset('Items')->search( |
979 | {}, |
0132e136 |
980 | { |
ac2803ef |
981 | select => [ { sum => 'Cost' } ], |
d676881f |
982 | as => [ 'total_cost' ], # remember this 'as' is for DBIx::Class::ResultSet not SQL |
ac2803ef |
983 | } |
984 | ); |
985 | my $tc = $rs->first->get_column('total_cost'); |
986 | |
987 | Or, you can use the L<DBIx::Class::ResultSetColumn>, which gets |
988 | returned when you ask the C<ResultSet> for a column using |
989 | C<get_column>: |
990 | |
991 | my $cost = $schema->resultset('Items')->get_column('Cost'); |
992 | my $tc = $cost->sum; |
993 | |
994 | With this you can also do: |
995 | |
996 | my $minvalue = $cost->min; |
997 | my $maxvalue = $cost->max; |
998 | |
999 | Or just iterate through the values of this column only: |
1000 | |
1001 | while ( my $c = $cost->next ) { |
1002 | print $c; |
1003 | } |
1004 | |
1005 | foreach my $c ($cost->all) { |
1006 | print $c; |
1007 | } |
1008 | |
0132e136 |
1009 | C<ResultSetColumn> only has a limited number of built-in functions. If |
709353af |
1010 | you need one that it doesn't have, then you can use the C<func> method |
1011 | instead: |
1012 | |
1013 | my $avg = $cost->func('AVERAGE'); |
1014 | |
1015 | This will cause the following SQL statement to be run: |
1016 | |
1017 | SELECT AVERAGE(Cost) FROM Items me |
1018 | |
1019 | Which will of course only work if your database supports this function. |
ac2803ef |
1020 | See L<DBIx::Class::ResultSetColumn> for more documentation. |
1021 | |
204e5c03 |
1022 | =head2 Creating a result set from a set of rows |
1023 | |
0132e136 |
1024 | Sometimes you have a (set of) row objects that you want to put into a |
204e5c03 |
1025 | resultset without the need to hit the DB again. You can do that by using the |
1026 | L<set_cache|DBIx::Class::Resultset/set_cache> method: |
1027 | |
2d7a4e46 |
1028 | my @uploadable_groups; |
204e5c03 |
1029 | while (my $group = $groups->next) { |
1030 | if ($group->can_upload($self)) { |
1031 | push @uploadable_groups, $group; |
1032 | } |
1033 | } |
1034 | my $new_rs = $self->result_source->resultset; |
1035 | $new_rs->set_cache(\@uploadable_groups); |
1036 | return $new_rs; |
1037 | |
1038 | |
d2f3e87b |
1039 | =head1 USING RELATIONSHIPS |
acee4e4d |
1040 | |
d2f3e87b |
1041 | =head2 Create a new row in a related table |
acee4e4d |
1042 | |
6f1434fd |
1043 | my $author = $book->create_related('author', { name => 'Fred'}); |
acee4e4d |
1044 | |
d2f3e87b |
1045 | =head2 Search in a related table |
acee4e4d |
1046 | |
1047 | Only searches for books named 'Titanic' by the author in $author. |
1048 | |
6f1434fd |
1049 | my $books_rs = $author->search_related('books', { name => 'Titanic' }); |
acee4e4d |
1050 | |
d2f3e87b |
1051 | =head2 Delete data in a related table |
acee4e4d |
1052 | |
1053 | Deletes only the book named Titanic by the author in $author. |
1054 | |
6f1434fd |
1055 | $author->delete_related('books', { name => 'Titanic' }); |
acee4e4d |
1056 | |
d2f3e87b |
1057 | =head2 Ordering a relationship result set |
f8bad769 |
1058 | |
0132e136 |
1059 | If you always want a relation to be ordered, you can specify this when you |
f8bad769 |
1060 | create the relationship. |
1061 | |
6f1434fd |
1062 | To order C<< $book->pages >> by descending page_number, create the relation |
1063 | as follows: |
f8bad769 |
1064 | |
6f1434fd |
1065 | __PACKAGE__->has_many('pages' => 'Page', 'book', { order_by => \'page_number DESC'} ); |
f8bad769 |
1066 | |
7c0825ab |
1067 | =head2 Filtering a relationship result set |
1068 | |
1069 | If you want to get a filtered result set, you can just add add to $attr as follows: |
1070 | |
1071 | __PACKAGE__->has_many('pages' => 'Page', 'book', { where => { scrap => 0 } } ); |
1072 | |
d2f3e87b |
1073 | =head2 Many-to-many relationships |
f8bad769 |
1074 | |
d2f3e87b |
1075 | This is straightforward using L<ManyToMany|DBIx::Class::Relationship/many_to_many>: |
f8bad769 |
1076 | |
d2f3e87b |
1077 | package My::User; |
6f1434fd |
1078 | use base 'DBIx::Class'; |
1079 | __PACKAGE__->load_components('Core'); |
d2f3e87b |
1080 | __PACKAGE__->table('user'); |
1081 | __PACKAGE__->add_columns(qw/id name/); |
1082 | __PACKAGE__->set_primary_key('id'); |
1083 | __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'user'); |
1084 | __PACKAGE__->many_to_many('addresses' => 'user_address', 'address'); |
87980de7 |
1085 | |
d2f3e87b |
1086 | package My::UserAddress; |
6f1434fd |
1087 | use base 'DBIx::Class'; |
1088 | __PACKAGE__->load_components('Core'); |
d2f3e87b |
1089 | __PACKAGE__->table('user_address'); |
1090 | __PACKAGE__->add_columns(qw/user address/); |
1091 | __PACKAGE__->set_primary_key(qw/user address/); |
1092 | __PACKAGE__->belongs_to('user' => 'My::User'); |
1093 | __PACKAGE__->belongs_to('address' => 'My::Address'); |
181a28f4 |
1094 | |
d2f3e87b |
1095 | package My::Address; |
6f1434fd |
1096 | use base 'DBIx::Class'; |
1097 | __PACKAGE__->load_components('Core'); |
d2f3e87b |
1098 | __PACKAGE__->table('address'); |
1099 | __PACKAGE__->add_columns(qw/id street town area_code country/); |
1100 | __PACKAGE__->set_primary_key('id'); |
1101 | __PACKAGE__->has_many('user_address' => 'My::UserAddress', 'address'); |
1102 | __PACKAGE__->many_to_many('users' => 'user_address', 'user'); |
1103 | |
1104 | $rs = $user->addresses(); # get all addresses for a user |
1105 | $rs = $address->users(); # get all users for an address |
1106 | |
db2b2eb6 |
1107 | =head2 Relationships across DB schemas |
1108 | |
1109 | Mapping relationships across L<DB schemas|DBIx::Class::Manual::Glossary/DB schema> |
1110 | is easy as long as the schemas themselves are all accessible via the same DBI |
1111 | connection. In most cases, this means that they are on the same database host |
1112 | as each other and your connecting database user has the proper permissions to them. |
1113 | |
1114 | To accomplish this one only needs to specify the DB schema name in the table |
1115 | declaration, like so... |
1116 | |
1117 | package MyDatabase::Main::Artist; |
1118 | use base qw/DBIx::Class/; |
1119 | __PACKAGE__->load_components(qw/PK::Auto Core/); |
0132e136 |
1120 | |
db2b2eb6 |
1121 | __PACKAGE__->table('database1.artist'); # will use "database1.artist" in FROM clause |
0132e136 |
1122 | |
cd87b928 |
1123 | __PACKAGE__->add_columns(qw/ artist_id name /); |
1124 | __PACKAGE__->set_primary_key('artist_id'); |
db2b2eb6 |
1125 | __PACKAGE__->has_many('cds' => 'MyDatabase::Main::Cd'); |
1126 | |
1127 | 1; |
1128 | |
1129 | Whatever string you specify there will be used to build the "FROM" clause in SQL |
1130 | queries. |
1131 | |
1132 | The big drawback to this is you now have DB schema names hardcoded in your |
1133 | class files. This becomes especially troublesome if you have multiple instances |
1134 | of your application to support a change lifecycle (e.g. DEV, TEST, PROD) and |
1135 | the DB schemas are named based on the environment (e.g. database1_dev). |
1136 | |
1137 | However, one can dynamically "map" to the proper DB schema by overriding the |
1138 | L<connection|DBIx::Class::Schama/connection> method in your Schema class and |
1139 | building a renaming facility, like so: |
1140 | |
1141 | package MyDatabase::Schema; |
1142 | use Moose; |
0132e136 |
1143 | |
db2b2eb6 |
1144 | extends 'DBIx::Class::Schema'; |
0132e136 |
1145 | |
db2b2eb6 |
1146 | around connection => sub { |
1147 | my ( $inner, $self, $dsn, $username, $pass, $attr ) = ( shift, @_ ); |
0132e136 |
1148 | |
db2b2eb6 |
1149 | my $postfix = delete $attr->{schema_name_postfix}; |
0132e136 |
1150 | |
db2b2eb6 |
1151 | $inner->(@_); |
0132e136 |
1152 | |
db2b2eb6 |
1153 | if ( $postfix ) { |
1154 | $self->append_db_name($postfix); |
1155 | } |
1156 | }; |
1157 | |
1158 | sub append_db_name { |
1159 | my ( $self, $postfix ) = @_; |
0132e136 |
1160 | |
1161 | my @sources_with_db |
1162 | = grep |
1163 | { $_->name =~ /^\w+\./mx } |
1164 | map |
1165 | { $self->source($_) } |
db2b2eb6 |
1166 | $self->sources; |
0132e136 |
1167 | |
db2b2eb6 |
1168 | foreach my $source (@sources_with_db) { |
1169 | my $name = $source->name; |
1170 | $name =~ s{^(\w+)\.}{${1}${postfix}\.}mx; |
0132e136 |
1171 | |
db2b2eb6 |
1172 | $source->name($name); |
1173 | } |
1174 | } |
1175 | |
1176 | 1; |
1177 | |
1178 | By overridding the L<connection|DBIx::Class::Schama/connection> |
1179 | method and extracting a custom option from the provided \%attr hashref one can |
1180 | then simply iterate over all the Schema's ResultSources, renaming them as |
1181 | needed. |
1182 | |
0132e136 |
1183 | To use this facility, simply add or modify the \%attr hashref that is passed to |
db2b2eb6 |
1184 | L<connection|DBIx::Class::Schama/connect>, as follows: |
1185 | |
0132e136 |
1186 | my $schema |
db2b2eb6 |
1187 | = MyDatabase::Schema->connect( |
0132e136 |
1188 | $dsn, |
1189 | $user, |
db2b2eb6 |
1190 | $pass, |
1191 | { |
1192 | schema_name_postfix => '_dev' |
0132e136 |
1193 | # ... Other options as desired ... |
db2b2eb6 |
1194 | }) |
1195 | |
1196 | Obviously, one could accomplish even more advanced mapping via a hash map or a |
1197 | callback routine. |
1198 | |
d2f3e87b |
1199 | =head1 TRANSACTIONS |
1200 | |
1201 | As of version 0.04001, there is improved transaction support in |
1202 | L<DBIx::Class::Storage> and L<DBIx::Class::Schema>. Here is an |
1203 | example of the recommended way to use it: |
1204 | |
1205 | my $genus = $schema->resultset('Genus')->find(12); |
1206 | |
1207 | my $coderef2 = sub { |
1208 | $genus->extinct(1); |
1209 | $genus->update; |
1210 | }; |
70634260 |
1211 | |
181a28f4 |
1212 | my $coderef1 = sub { |
35d4fe78 |
1213 | $genus->add_to_species({ name => 'troglodyte' }); |
1214 | $genus->wings(2); |
1215 | $genus->update; |
6f1434fd |
1216 | $schema->txn_do($coderef2); # Can have a nested transaction. Only the outer will actualy commit |
181a28f4 |
1217 | return $genus->species; |
1218 | }; |
1219 | |
181a28f4 |
1220 | my $rs; |
1221 | eval { |
70634260 |
1222 | $rs = $schema->txn_do($coderef1); |
181a28f4 |
1223 | }; |
1224 | |
1225 | if ($@) { # Transaction failed |
1226 | die "the sky is falling!" # |
1227 | if ($@ =~ /Rollback failed/); # Rollback failed |
1228 | |
1229 | deal_with_failed_transaction(); |
35d4fe78 |
1230 | } |
87980de7 |
1231 | |
181a28f4 |
1232 | Nested transactions will work as expected. That is, only the outermost |
1233 | transaction will actually issue a commit to the $dbh, and a rollback |
1234 | at any level of any transaction will cause the entire nested |
1235 | transaction to fail. Support for savepoints and for true nested |
40dbc108 |
1236 | transactions (for databases that support them) will hopefully be added |
1237 | in the future. |
ee38fa40 |
1238 | |
0132e136 |
1239 | =head1 SQL |
ee38fa40 |
1240 | |
d2f3e87b |
1241 | =head2 Creating Schemas From An Existing Database |
ea6309e2 |
1242 | |
0132e136 |
1243 | L<DBIx::Class::Schema::Loader> will connect to a database and create a |
d2f3e87b |
1244 | L<DBIx::Class::Schema> and associated sources by examining the database. |
bade79c4 |
1245 | |
0132e136 |
1246 | The recommend way of achieving this is to use the |
d2f3e87b |
1247 | L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> method: |
bade79c4 |
1248 | |
6f1434fd |
1249 | perl -MDBIx::Class::Schema::Loader=make_schema_at,dump_to_dir:./lib \ |
1250 | -e 'make_schema_at("My::Schema", { debug => 1 }, [ "dbi:Pg:dbname=foo","postgres" ])' |
362500af |
1251 | |
d2f3e87b |
1252 | This will create a tree of files rooted at C<./lib/My/Schema/> containing |
1253 | source definitions for all the tables found in the C<foo> database. |
362500af |
1254 | |
d2f3e87b |
1255 | =head2 Creating DDL SQL |
362500af |
1256 | |
264f1571 |
1257 | The following functionality requires you to have L<SQL::Translator> |
1258 | (also known as "SQL Fairy") installed. |
362500af |
1259 | |
264f1571 |
1260 | To create a set of database-specific .sql files for the above schema: |
362500af |
1261 | |
264f1571 |
1262 | my $schema = My::Schema->connect($dsn); |
1263 | $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'], |
1264 | '0.1', |
d2f3e87b |
1265 | './dbscriptdir/' |
264f1571 |
1266 | ); |
1267 | |
1268 | By default this will create schema files in the current directory, for |
1269 | MySQL, SQLite and PostgreSQL, using the $VERSION from your Schema.pm. |
1270 | |
1271 | To create a new database using the schema: |
1272 | |
1273 | my $schema = My::Schema->connect($dsn); |
1274 | $schema->deploy({ add_drop_tables => 1}); |
1275 | |
1276 | To import created .sql files using the mysql client: |
1277 | |
1278 | mysql -h "host" -D "database" -u "user" -p < My_Schema_1.0_MySQL.sql |
1279 | |
1280 | To create C<ALTER TABLE> conversion scripts to update a database to a |
1281 | newer version of your schema at a later point, first set a new |
d2f3e87b |
1282 | C<$VERSION> in your Schema file, then: |
264f1571 |
1283 | |
1284 | my $schema = My::Schema->connect($dsn); |
1285 | $schema->create_ddl_dir(['MySQL', 'SQLite', 'PostgreSQL'], |
1286 | '0.2', |
1287 | '/dbscriptdir/', |
1288 | '0.1' |
1289 | ); |
1290 | |
1291 | This will produce new database-specific .sql files for the new version |
1292 | of the schema, plus scripts to convert from version 0.1 to 0.2. This |
1293 | requires that the files for 0.1 as created above are available in the |
1294 | given directory to diff against. |
362500af |
1295 | |
6f1434fd |
1296 | =head2 Select from dual |
16cd5b28 |
1297 | |
1298 | Dummy tables are needed by some databases to allow calling functions |
1299 | or expressions that aren't based on table content, for examples of how |
1300 | this applies to various database types, see: |
1301 | L<http://troels.arvin.dk/db/rdbms/#other-dummy_table>. |
1302 | |
1303 | Note: If you're using Oracles dual table don't B<ever> do anything |
1304 | other than a select, if you CRUD on your dual table you *will* break |
1305 | your database. |
1306 | |
1307 | Make a table class as you would for any other table |
0132e136 |
1308 | |
16cd5b28 |
1309 | package MyAppDB::Dual; |
1310 | use strict; |
1311 | use warnings; |
1312 | use base 'DBIx::Class'; |
1313 | __PACKAGE__->load_components("Core"); |
1314 | __PACKAGE__->table("Dual"); |
1315 | __PACKAGE__->add_columns( |
1316 | "dummy", |
1317 | { data_type => "VARCHAR2", is_nullable => 0, size => 1 }, |
1318 | ); |
0132e136 |
1319 | |
16cd5b28 |
1320 | Once you've loaded your table class select from it using C<select> |
1321 | and C<as> instead of C<columns> |
0132e136 |
1322 | |
16cd5b28 |
1323 | my $rs = $schema->resultset('Dual')->search(undef, |
1324 | { select => [ 'sydate' ], |
1325 | as => [ 'now' ] |
1326 | }, |
1327 | ); |
0132e136 |
1328 | |
16cd5b28 |
1329 | All you have to do now is be careful how you access your resultset, the below |
1330 | will not work because there is no column called 'now' in the Dual table class |
0132e136 |
1331 | |
16cd5b28 |
1332 | while (my $dual = $rs->next) { |
1333 | print $dual->now."\n"; |
1334 | } |
6f1434fd |
1335 | # Can't locate object method "now" via package "MyAppDB::Dual" at headshot.pl line 23. |
0132e136 |
1336 | |
16cd5b28 |
1337 | You could of course use 'dummy' in C<as> instead of 'now', or C<add_columns> to |
1338 | your Dual class for whatever you wanted to select from dual, but that's just |
1339 | silly, instead use C<get_column> |
0132e136 |
1340 | |
16cd5b28 |
1341 | while (my $dual = $rs->next) { |
1342 | print $dual->get_column('now')."\n"; |
1343 | } |
0132e136 |
1344 | |
16cd5b28 |
1345 | Or use C<cursor> |
0132e136 |
1346 | |
16cd5b28 |
1347 | my $cursor = $rs->cursor; |
1348 | while (my @vals = $cursor->next) { |
1349 | print $vals[0]."\n"; |
1350 | } |
336256bc |
1351 | |
1352 | In case you're going to use this "trick" together with L<DBIx::Class::Schema/deploy> or |
1353 | L<DBIx::Class::Schema/create_ddl_dir> a table called "dual" will be created in your |
1354 | current schema. This would overlap "sys.dual" and you could not fetch "sysdate" or |
1355 | "sequence.nextval" anymore from dual. To avoid this problem, just tell |
1356 | L<SQL::Translator> to not create table dual: |
1357 | |
1358 | my $sqlt_args = { |
1359 | add_drop_table => 1, |
1360 | parser_args => { sources => [ grep $_ ne 'Dual', schema->sources ] }, |
1361 | }; |
1362 | $schema->create_ddl_dir( [qw/Oracle/], undef, './sql', undef, $sqlt_args ); |
0132e136 |
1363 | |
16cd5b28 |
1364 | Or use L<DBIx::Class::ResultClass::HashRefInflator> |
0132e136 |
1365 | |
16cd5b28 |
1366 | $rs->result_class('DBIx::Class::ResultClass::HashRefInflator'); |
1367 | while ( my $dual = $rs->next ) { |
1368 | print $dual->{now}."\n"; |
1369 | } |
0132e136 |
1370 | |
16cd5b28 |
1371 | Here are some example C<select> conditions to illustrate the different syntax |
0132e136 |
1372 | you could use for doing stuff like |
16cd5b28 |
1373 | C<oracles.heavily(nested(functions_can('take', 'lots'), OF), 'args')> |
0132e136 |
1374 | |
16cd5b28 |
1375 | # get a sequence value |
1376 | select => [ 'A_SEQ.nextval' ], |
0132e136 |
1377 | |
16cd5b28 |
1378 | # get create table sql |
1379 | select => [ { 'dbms_metadata.get_ddl' => [ "'TABLE'", "'ARTIST'" ]} ], |
0132e136 |
1380 | |
16cd5b28 |
1381 | # get a random num between 0 and 100 |
1382 | select => [ { "trunc" => [ { "dbms_random.value" => [0,100] } ]} ], |
0132e136 |
1383 | |
16cd5b28 |
1384 | # what year is it? |
1385 | select => [ { 'extract' => [ \'year from sysdate' ] } ], |
0132e136 |
1386 | |
16cd5b28 |
1387 | # do some math |
1388 | select => [ {'round' => [{'cos' => [ \'180 * 3.14159265359/180' ]}]}], |
0132e136 |
1389 | |
16cd5b28 |
1390 | # which day of the week were you born on? |
6f1434fd |
1391 | select => [{'to_char' => [{'to_date' => [ "'25-DEC-1980'", "'dd-mon-yyyy'" ]}, "'day'"]}], |
0132e136 |
1392 | |
16cd5b28 |
1393 | # select 16 rows from dual |
1394 | select => [ "'hello'" ], |
1395 | as => [ 'world' ], |
1396 | group_by => [ 'cube( 1, 2, 3, 4 )' ], |
0132e136 |
1397 | |
1398 | |
16cd5b28 |
1399 | |
d2f3e87b |
1400 | =head2 Adding Indexes And Functions To Your SQL |
362500af |
1401 | |
d2f3e87b |
1402 | Often you will want indexes on columns on your table to speed up searching. To |
0132e136 |
1403 | do this, create a method called C<sqlt_deploy_hook> in the relevant source |
1404 | class (refer to the advanced |
2d7d8459 |
1405 | L<callback system|DBIx::Class::ResultSource/sqlt_deploy_callback> if you wish |
1406 | to share a hook between multiple sources): |
b0a20454 |
1407 | |
23471103 |
1408 | package My::Schema::Result::Artist; |
b0a20454 |
1409 | |
d2f3e87b |
1410 | __PACKAGE__->table('artist'); |
1411 | __PACKAGE__->add_columns(id => { ... }, name => { ... }) |
b0a20454 |
1412 | |
d2f3e87b |
1413 | sub sqlt_deploy_hook { |
1414 | my ($self, $sqlt_table) = @_; |
1415 | |
1416 | $sqlt_table->add_index(name => 'idx_name', fields => ['name']); |
1417 | } |
1418 | |
1419 | 1; |
1420 | |
0132e136 |
1421 | Sometimes you might want to change the index depending on the type of the |
d2f3e87b |
1422 | database for which SQL is being generated: |
1423 | |
1424 | my ($db_type = $sqlt_table->schema->translator->producer_type) |
1425 | =~ s/^SQL::Translator::Producer:://; |
1426 | |
0132e136 |
1427 | You can also add hooks to the schema level to stop certain tables being |
d2f3e87b |
1428 | created: |
1429 | |
1430 | package My::Schema; |
1431 | |
1432 | ... |
1433 | |
1434 | sub sqlt_deploy_hook { |
1435 | my ($self, $sqlt_schema) = @_; |
1436 | |
1437 | $sqlt_schema->drop_table('table_name'); |
1438 | } |
1439 | |
2d7d8459 |
1440 | You could also add views, procedures or triggers to the output using |
1441 | L<SQL::Translator::Schema/add_view>, |
1442 | L<SQL::Translator::Schema/add_procedure> or |
1443 | L<SQL::Translator::Schema/add_trigger>. |
1444 | |
b0a20454 |
1445 | |
362500af |
1446 | =head2 Schema versioning |
1447 | |
1448 | The following example shows simplistically how you might use DBIx::Class to |
1449 | deploy versioned schemas to your customers. The basic process is as follows: |
1450 | |
da4779ad |
1451 | =over 4 |
1452 | |
1453 | =item 1. |
1454 | |
1455 | Create a DBIx::Class schema |
1456 | |
1457 | =item 2. |
1458 | |
1459 | Save the schema |
1460 | |
1461 | =item 3. |
1462 | |
1463 | Deploy to customers |
1464 | |
1465 | =item 4. |
1466 | |
1467 | Modify schema to change functionality |
1468 | |
1469 | =item 5. |
1470 | |
1471 | Deploy update to customers |
1472 | |
1473 | =back |
362500af |
1474 | |
d2f3e87b |
1475 | B<Create a DBIx::Class schema> |
362500af |
1476 | |
1477 | This can either be done manually, or generated from an existing database as |
d2f3e87b |
1478 | described under L</Creating Schemas From An Existing Database> |
362500af |
1479 | |
d2f3e87b |
1480 | B<Save the schema> |
362500af |
1481 | |
d2f3e87b |
1482 | Call L<DBIx::Class::Schema/create_ddl_dir> as above under L</Creating DDL SQL>. |
362500af |
1483 | |
d2f3e87b |
1484 | B<Deploy to customers> |
362500af |
1485 | |
1486 | There are several ways you could deploy your schema. These are probably |
1487 | beyond the scope of this recipe, but might include: |
1488 | |
da4779ad |
1489 | =over 4 |
1490 | |
1491 | =item 1. |
1492 | |
1493 | Require customer to apply manually using their RDBMS. |
1494 | |
1495 | =item 2. |
1496 | |
1497 | Package along with your app, making database dump/schema update/tests |
362500af |
1498 | all part of your install. |
1499 | |
da4779ad |
1500 | =back |
1501 | |
d2f3e87b |
1502 | B<Modify the schema to change functionality> |
362500af |
1503 | |
264f1571 |
1504 | As your application evolves, it may be necessary to modify your schema |
1505 | to change functionality. Once the changes are made to your schema in |
1506 | DBIx::Class, export the modified schema and the conversion scripts as |
d2f3e87b |
1507 | in L</Creating DDL SQL>. |
362500af |
1508 | |
d2f3e87b |
1509 | B<Deploy update to customers> |
362500af |
1510 | |
264f1571 |
1511 | Add the L<DBIx::Class::Schema::Versioned> schema component to your |
1512 | Schema class. This will add a new table to your database called |
ecea7937 |
1513 | C<dbix_class_schema_vesion> which will keep track of which version is installed |
264f1571 |
1514 | and warn if the user trys to run a newer schema version than the |
1515 | database thinks it has. |
1516 | |
1517 | Alternatively, you can send the conversion sql scripts to your |
1518 | customers as above. |
362500af |
1519 | |
0132e136 |
1520 | =head2 Setting quoting for the generated SQL. |
d2f3e87b |
1521 | |
1522 | If the database contains column names with spaces and/or reserved words, they |
1523 | need to be quoted in the SQL queries. This is done using: |
1524 | |
1525 | __PACKAGE__->storage->sql_maker->quote_char([ qw/[ ]/] ); |
1526 | __PACKAGE__->storage->sql_maker->name_sep('.'); |
1527 | |
1528 | The first sets the quote characters. Either a pair of matching |
1529 | brackets, or a C<"> or C<'>: |
0132e136 |
1530 | |
d2f3e87b |
1531 | __PACKAGE__->storage->sql_maker->quote_char('"'); |
1532 | |
1533 | Check the documentation of your database for the correct quote |
1534 | characters to use. C<name_sep> needs to be set to allow the SQL |
1535 | generator to put the quotes the correct place. |
1536 | |
0132e136 |
1537 | In most cases you should set these as part of the arguments passed to |
d68b0c69 |
1538 | L<DBIx::Class::Schema/connect>: |
d2f3e87b |
1539 | |
1540 | my $schema = My::Schema->connect( |
1541 | 'dbi:mysql:my_db', |
1542 | 'db_user', |
1543 | 'db_password', |
1544 | { |
1545 | quote_char => '"', |
1546 | name_sep => '.' |
1547 | } |
1548 | ) |
1549 | |
7be93b07 |
1550 | =head2 Setting limit dialect for SQL::Abstract::Limit |
1551 | |
324572ca |
1552 | In some cases, SQL::Abstract::Limit cannot determine the dialect of |
1553 | the remote SQL server by looking at the database handle. This is a |
1554 | common problem when using the DBD::JDBC, since the DBD-driver only |
1555 | know that in has a Java-driver available, not which JDBC driver the |
1556 | Java component has loaded. This specifically sets the limit_dialect |
1557 | to Microsoft SQL-server (See more names in SQL::Abstract::Limit |
1558 | -documentation. |
7be93b07 |
1559 | |
1560 | __PACKAGE__->storage->sql_maker->limit_dialect('mssql'); |
1561 | |
324572ca |
1562 | The JDBC bridge is one way of getting access to a MSSQL server from a platform |
7be93b07 |
1563 | that Microsoft doesn't deliver native client libraries for. (e.g. Linux) |
1564 | |
0132e136 |
1565 | The limit dialect can also be set at connect time by specifying a |
d2f3e87b |
1566 | C<limit_dialect> key in the final hash as shown above. |
2437a1e3 |
1567 | |
05697a49 |
1568 | =head2 Working with PostgreSQL array types |
1569 | |
20ea616f |
1570 | You can also assign values to PostgreSQL array columns by passing array |
1571 | references in the C<\%columns> (C<\%vals>) hashref of the |
1572 | L<DBIx::Class::ResultSet/create> and L<DBIx::Class::Row/update> family of |
1573 | methods: |
05697a49 |
1574 | |
1575 | $resultset->create({ |
1576 | numbers => [1, 2, 3] |
1577 | }); |
1578 | |
1579 | $row->update( |
1580 | { |
1581 | numbers => [1, 2, 3] |
1582 | }, |
1583 | { |
1584 | day => '2008-11-24' |
1585 | } |
1586 | ); |
1587 | |
1588 | In conditions (eg. C<\%cond> in the L<DBIx::Class::ResultSet/search> family of |
1589 | methods) you cannot directly use array references (since this is interpreted as |
1590 | a list of values to be C<OR>ed), but you can use the following syntax to force |
1591 | passing them as bind values: |
1592 | |
1593 | $resultset->search( |
1594 | { |
31eb3263 |
1595 | numbers => \[ '= ?', [numbers => [1, 2, 3]] ] |
05697a49 |
1596 | } |
1597 | ); |
1598 | |
1599 | See L<SQL::Abstract/array_datatypes> and L<SQL::Abstract/Literal SQL with |
31eb3263 |
1600 | placeholders and bind values (subqueries)> for more explanation. Note that |
1601 | L<DBIx::Class> sets L<SQL::Abstract/bindtype> to C<columns>, so you must pass |
1602 | the bind values (the C<[1, 2, 3]> arrayref in the above example) wrapped in |
1603 | arrayrefs together with the column name, like this: C<< [column_name => value] |
1604 | >>. |
05697a49 |
1605 | |
0132e136 |
1606 | =head1 BOOTSTRAPPING/MIGRATING |
2437a1e3 |
1607 | |
d2f3e87b |
1608 | =head2 Easy migration from class-based to schema-based setup |
2437a1e3 |
1609 | |
d2f3e87b |
1610 | You want to start using the schema-based approach to L<DBIx::Class> |
1611 | (see L<SchemaIntro.pod>), but have an established class-based setup with lots |
1612 | of existing classes that you don't want to move by hand. Try this nifty script |
1613 | instead: |
1614 | |
1615 | use MyDB; |
1616 | use SQL::Translator; |
0132e136 |
1617 | |
d2f3e87b |
1618 | my $schema = MyDB->schema_instance; |
0132e136 |
1619 | |
1620 | my $translator = SQL::Translator->new( |
d2f3e87b |
1621 | debug => $debug || 0, |
1622 | trace => $trace || 0, |
1623 | no_comments => $no_comments || 0, |
1624 | show_warnings => $show_warnings || 0, |
1625 | add_drop_table => $add_drop_table || 0, |
1626 | validate => $validate || 0, |
1627 | parser_args => { |
1628 | 'DBIx::Schema' => $schema, |
1629 | }, |
1630 | producer_args => { |
1631 | 'prefix' => 'My::Schema', |
1632 | }, |
1633 | ); |
0132e136 |
1634 | |
d2f3e87b |
1635 | $translator->parser('SQL::Translator::Parser::DBIx::Class'); |
1636 | $translator->producer('SQL::Translator::Producer::DBIx::Class::File'); |
0132e136 |
1637 | |
d2f3e87b |
1638 | my $output = $translator->translate(@args) or die |
1639 | "Error: " . $translator->error; |
0132e136 |
1640 | |
d2f3e87b |
1641 | print $output; |
2437a1e3 |
1642 | |
d2f3e87b |
1643 | You could use L<Module::Find> to search for all subclasses in the MyDB::* |
1644 | namespace, which is currently left as an exercise for the reader. |
2437a1e3 |
1645 | |
d2f3e87b |
1646 | =head1 OVERLOADING METHODS |
086b93a2 |
1647 | |
ab872312 |
1648 | L<DBIx::Class> uses the L<Class::C3> package, which provides for redispatch of |
1649 | method calls, useful for things like default values and triggers. You have to |
1650 | use calls to C<next::method> to overload methods. More information on using |
1651 | L<Class::C3> with L<DBIx::Class> can be found in |
086b93a2 |
1652 | L<DBIx::Class::Manual::Component>. |
1653 | |
d2f3e87b |
1654 | =head2 Setting default values for a row |
1655 | |
1656 | It's as simple as overriding the C<new> method. Note the use of |
1657 | C<next::method>. |
1658 | |
1659 | sub new { |
1660 | my ( $class, $attrs ) = @_; |
1661 | |
1662 | $attrs->{foo} = 'bar' unless defined $attrs->{foo}; |
1663 | |
1664 | my $new = $class->next::method($attrs); |
1665 | |
1666 | return $new; |
1667 | } |
1668 | |
0132e136 |
1669 | For more information about C<next::method>, look in the L<Class::C3> |
d2f3e87b |
1670 | documentation. See also L<DBIx::Class::Manual::Component> for more |
1671 | ways to write your own base classes to do this. |
1672 | |
1673 | People looking for ways to do "triggers" with DBIx::Class are probably |
0132e136 |
1674 | just looking for this. |
d2f3e87b |
1675 | |
1676 | =head2 Changing one field whenever another changes |
086b93a2 |
1677 | |
0132e136 |
1678 | For example, say that you have three columns, C<id>, C<number>, and |
086b93a2 |
1679 | C<squared>. You would like to make changes to C<number> and have |
1680 | C<squared> be automagically set to the value of C<number> squared. |
1681 | You can accomplish this by overriding C<store_column>: |
1682 | |
1683 | sub store_column { |
1684 | my ( $self, $name, $value ) = @_; |
1685 | if ($name eq 'number') { |
1686 | $self->squared($value * $value); |
1687 | } |
1688 | $self->next::method($name, $value); |
1689 | } |
1690 | |
1691 | Note that the hard work is done by the call to C<next::method>, which |
324572ca |
1692 | redispatches your call to store_column in the superclass(es). |
086b93a2 |
1693 | |
d2f3e87b |
1694 | =head2 Automatically creating related objects |
086b93a2 |
1695 | |
0132e136 |
1696 | You might have a class C<Artist> which has many C<CD>s. Further, you |
086b93a2 |
1697 | want to create a C<CD> object every time you insert an C<Artist> object. |
ccbebdbc |
1698 | You can accomplish this by overriding C<insert> on your objects: |
086b93a2 |
1699 | |
1700 | sub insert { |
ccbebdbc |
1701 | my ( $self, @args ) = @_; |
1702 | $self->next::method(@args); |
086b93a2 |
1703 | $self->cds->new({})->fill_from_artist($self)->insert; |
1704 | return $self; |
1705 | } |
1706 | |
1707 | where C<fill_from_artist> is a method you specify in C<CD> which sets |
1708 | values in C<CD> based on the data in the C<Artist> object you pass in. |
1709 | |
d2f3e87b |
1710 | =head2 Wrapping/overloading a column accessor |
1711 | |
1712 | B<Problem:> |
1713 | |
1714 | Say you have a table "Camera" and want to associate a description |
1715 | with each camera. For most cameras, you'll be able to generate the description from |
1716 | the other columns. However, in a few special cases you may want to associate a |
1717 | custom description with a camera. |
1718 | |
1719 | B<Solution:> |
1720 | |
1721 | In your database schema, define a description field in the "Camera" table that |
1722 | can contain text and null values. |
1723 | |
1724 | In DBIC, we'll overload the column accessor to provide a sane default if no |
1725 | custom description is defined. The accessor will either return or generate the |
1726 | description, depending on whether the field is null or not. |
1727 | |
1728 | First, in your "Camera" schema class, define the description field as follows: |
1729 | |
1730 | __PACKAGE__->add_columns(description => { accessor => '_description' }); |
1731 | |
1732 | Next, we'll define the accessor-wrapper subroutine: |
1733 | |
1734 | sub description { |
1735 | my $self = shift; |
1736 | |
1737 | # If there is an update to the column, we'll let the original accessor |
1738 | # deal with it. |
1739 | return $self->_description(@_) if @_; |
1740 | |
1741 | # Fetch the column value. |
1742 | my $description = $self->_description; |
1743 | |
1744 | # If there's something in the description field, then just return that. |
1745 | return $description if defined $description && length $descripton; |
1746 | |
1747 | # Otherwise, generate a description. |
1748 | return $self->generate_description; |
1749 | } |
1750 | |
1751 | =head1 DEBUGGING AND PROFILING |
1752 | |
1753 | =head2 DBIx::Class objects with Data::Dumper |
1def3451 |
1754 | |
1755 | L<Data::Dumper> can be a very useful tool for debugging, but sometimes it can |
1756 | be hard to find the pertinent data in all the data it can generate. |
1757 | Specifically, if one naively tries to use it like so, |
1758 | |
1759 | use Data::Dumper; |
1760 | |
1761 | my $cd = $schema->resultset('CD')->find(1); |
1762 | print Dumper($cd); |
1763 | |
1764 | several pages worth of data from the CD object's schema and result source will |
1765 | be dumped to the screen. Since usually one is only interested in a few column |
1766 | values of the object, this is not very helpful. |
1767 | |
1768 | Luckily, it is possible to modify the data before L<Data::Dumper> outputs |
1769 | it. Simply define a hook that L<Data::Dumper> will call on the object before |
1770 | dumping it. For example, |
1771 | |
1772 | package My::DB::CD; |
1773 | |
1774 | sub _dumper_hook { |
99fb1058 |
1775 | $_[0] = bless { |
1776 | %{ $_[0] }, |
1def3451 |
1777 | result_source => undef, |
99fb1058 |
1778 | }, ref($_[0]); |
1def3451 |
1779 | } |
1780 | |
1781 | [...] |
1782 | |
1783 | use Data::Dumper; |
1784 | |
22139027 |
1785 | local $Data::Dumper::Freezer = '_dumper_hook'; |
1def3451 |
1786 | |
1787 | my $cd = $schema->resultset('CD')->find(1); |
1788 | print Dumper($cd); |
1789 | # dumps $cd without its ResultSource |
1790 | |
1791 | If the structure of your schema is such that there is a common base class for |
1792 | all your table classes, simply put a method similar to C<_dumper_hook> in the |
1793 | base class and set C<$Data::Dumper::Freezer> to its name and L<Data::Dumper> |
1794 | will automagically clean up your data before printing it. See |
1795 | L<Data::Dumper/EXAMPLES> for more information. |
1796 | |
4c248161 |
1797 | =head2 Profiling |
1798 | |
85f78622 |
1799 | When you enable L<DBIx::Class::Storage>'s debugging it prints the SQL |
4c248161 |
1800 | executed as well as notifications of query completion and transaction |
1801 | begin/commit. If you'd like to profile the SQL you can subclass the |
1802 | L<DBIx::Class::Storage::Statistics> class and write your own profiling |
1803 | mechanism: |
1804 | |
1805 | package My::Profiler; |
1806 | use strict; |
1807 | |
1808 | use base 'DBIx::Class::Storage::Statistics'; |
1809 | |
1810 | use Time::HiRes qw(time); |
1811 | |
1812 | my $start; |
1813 | |
1814 | sub query_start { |
1815 | my $self = shift(); |
1816 | my $sql = shift(); |
1817 | my $params = @_; |
1818 | |
70f39278 |
1819 | $self->print("Executing $sql: ".join(', ', @params)."\n"); |
4c248161 |
1820 | $start = time(); |
1821 | } |
1822 | |
1823 | sub query_end { |
1824 | my $self = shift(); |
1825 | my $sql = shift(); |
1826 | my @params = @_; |
1827 | |
70f39278 |
1828 | my $elapsed = sprintf("%0.4f", time() - $start); |
1829 | $self->print("Execution took $elapsed seconds.\n"); |
4c248161 |
1830 | $start = undef; |
1831 | } |
1832 | |
1833 | 1; |
1834 | |
1835 | You can then install that class as the debugging object: |
1836 | |
70f39278 |
1837 | __PACKAGE__->storage->debugobj(new My::Profiler()); |
1838 | __PACKAGE__->storage->debug(1); |
4c248161 |
1839 | |
1840 | A more complicated example might involve storing each execution of SQL in an |
1841 | array: |
1842 | |
1843 | sub query_end { |
1844 | my $self = shift(); |
1845 | my $sql = shift(); |
1846 | my @params = @_; |
1847 | |
1848 | my $elapsed = time() - $start; |
1849 | push(@{ $calls{$sql} }, { |
1850 | params => \@params, |
1851 | elapsed => $elapsed |
1852 | }); |
1853 | } |
1854 | |
1855 | You could then create average, high and low execution times for an SQL |
1856 | statement and dig down to see if certain parameters cause aberrant behavior. |
70f39278 |
1857 | You might want to check out L<DBIx::Class::QueryLog> as well. |
4c248161 |
1858 | |
bc96f260 |
1859 | =head1 STARTUP SPEED |
1860 | |
1861 | L<DBIx::Class|DBIx::Class> programs can have a significant startup delay |
1862 | as the ORM loads all the relevant classes. This section examines |
1863 | techniques for reducing the startup delay. |
1864 | |
1865 | These tips are are listed in order of decreasing effectiveness - so the |
1866 | first tip, if applicable, should have the greatest effect on your |
1867 | application. |
1868 | |
1869 | =head2 Statically Define Your Schema |
1870 | |
1871 | If you are using |
1872 | L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to build the |
1873 | classes dynamically based on the database schema then there will be a |
1874 | significant startup delay. |
1875 | |
1876 | For production use a statically defined schema (which can be generated |
1877 | using L<DBIx::Class::Schema::Loader|DBIx::Class::Schema::Loader> to dump |
1878 | the database schema once - see |
1879 | L<make_schema_at|DBIx::Class::Schema::Loader/make_schema_at> and |
1880 | L<dump_directory|DBIx::Class::Schema::Loader/dump_directory> for more |
1881 | details on creating static schemas from a database). |
1882 | |
1883 | =head2 Move Common Startup into a Base Class |
1884 | |
1885 | Typically L<DBIx::Class> result classes start off with |
1886 | |
1887 | use base qw/DBIx::Class/; |
1888 | __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/); |
1889 | |
1890 | If this preamble is moved into a common base class:- |
1891 | |
1892 | package MyDBICbase; |
0132e136 |
1893 | |
bc96f260 |
1894 | use base qw/DBIx::Class/; |
1895 | __PACKAGE__->load_components(qw/InflateColumn::DateTime Core/); |
1896 | 1; |
1897 | |
1898 | and each result class then uses this as a base:- |
1899 | |
1900 | use base qw/MyDBICbase/; |
1901 | |
1902 | then the load_components is only performed once, which can result in a |
1903 | considerable startup speedup for schemas with many classes. |
1904 | |
1905 | =head2 Explicitly List Schema Result Classes |
1906 | |
1907 | The schema class will normally contain |
1908 | |
1909 | __PACKAGE__->load_classes(); |
1910 | |
1911 | to load the result classes. This will use L<Module::Find|Module::Find> |
1912 | to find and load the appropriate modules. Explicitly defining the |
1913 | classes you wish to load will remove the overhead of |
0132e136 |
1914 | L<Module::Find|Module::Find> and the related directory operations: |
bc96f260 |
1915 | |
1916 | __PACKAGE__->load_classes(qw/ CD Artist Track /); |
1917 | |
1918 | If you are instead using the L<load_namespaces|DBIx::Class::Schema/load_namespaces> |
1919 | syntax to load the appropriate classes there is not a direct alternative |
1920 | avoiding L<Module::Find|Module::Find>. |
7aaec96c |
1921 | |
f4db5947 |
1922 | =head1 MEMORY USAGE |
1923 | |
1924 | =head2 Cached statements |
1925 | |
1926 | L<DBIx::Class> normally caches all statements with L<< prepare_cached()|DBI/prepare_cached >>. |
1927 | This is normally a good idea, but if too many statements are cached, the database may use too much |
1928 | memory and may eventually run out and fail entirely. If you suspect this may be the case, you may want |
1929 | to examine DBI's L<< CachedKids|DBI/CachedKidsCachedKids_(hash_ref) >> hash: |
1930 | |
1931 | # print all currently cached prepared statements |
1932 | print for keys %{$schema->storage->dbh->{CachedKids}}; |
1933 | # get a count of currently cached prepared statements |
1934 | my $count = scalar keys %{$schema->storage->dbh->{CachedKids}}; |
1935 | |
1936 | If it's appropriate, you can simply clear these statements, automatically deallocating them in the |
1937 | database: |
1938 | |
1939 | my $kids = $schema->storage->dbh->{CachedKids}; |
1940 | delete @{$kids}{keys %$kids} if scalar keys %$kids > 100; |
1941 | |
1942 | But what you probably want is to expire unused statements and not those that are used frequently. |
1943 | You can accomplish this with L<Tie::Cache> or L<Tie::Cache::LRU>: |
1944 | |
1945 | use Tie::Cache; |
1946 | use DB::Main; |
1947 | my $schema = DB::Main->connect($dbi_dsn, $user, $pass, { |
1948 | on_connect_do => sub { tie %{shift->_dbh->{CachedKids}}, 'Tie::Cache', 100 }, |
1949 | }); |
1950 | |
40dbc108 |
1951 | =cut |