Merged 14009:14059 from trunk.
[rails.git] / vendor / gems / composite_primary_keys-1.1.0 / website / index.txt
1 h1. Composite Primary Keys
2
3 h1. → Ruby on Rails
4
5 h1. → ActiveRecords
6
7 h2. What
8
9 Ruby on Rails does not support composite primary keys. This free software is an extension 
10 to the database layer of Rails - "ActiveRecords":http://wiki.rubyonrails.com/rails/pages/ActiveRecord - to support composite primary keys as transparently as possible.
11
12 Any Ruby script using ActiveRecords can use Composite Primary Keys with this library.
13
14 h2. Installing
15
16 <pre syntax="ruby">sudo gem install composite_primary_keys</pre>
17
18 Rails: Add the following to the bottom of your <code>environment.rb</code> file
19
20 <pre syntax="ruby">require 'composite_primary_keys'</pre>
21
22 Ruby scripts: Add the following to the top of your script
23
24 <pre syntax="ruby">require 'rubygems'
25 require 'composite_primary_keys'</pre>
26
27 h2. The basics
28
29 A model with composite primary keys would look like...
30
31 <pre syntax="ruby">class Membership < ActiveRecord::Base
32   # set_primary_keys *keys - turns on composite key functionality
33   set_primary_keys :user_id, :group_id
34   belongs_to :user
35   belongs_to :group
36   has_many :statuses, :class_name => 'MembershipStatus', :foreign_key => [:user_id, :group_id]
37 end</pre>
38
39 A model associated with a composite key model would be defined like...
40
41 <pre syntax="ruby">class MembershipStatus < ActiveRecord::Base
42   belongs_to :membership, :foreign_key => [:user_id, :group_id]
43 end</pre>
44
45 That is, associations can include composite keys too. Nice.
46
47 h2. Demonstration of usage
48
49 Once you've created your models to specify composite primary keys (such as the Membership class) and associations (such as MembershipStatus#membership), you can uses them like any normal model with associations.
50
51 But first, lets check out our primary keys.
52
53 <pre syntax="ruby">MembershipStatus.primary_key # => "id"    # normal single key
54 Membership.primary_key  # => [:user_id, :group_id] # composite keys
55 Membership.primary_key.to_s # => "user_id,group_id"</pre>
56
57 Now we want to be able to find instances using the same syntax we always use for ActiveRecords...
58
59 <pre syntax="ruby">MembershipStatus.find(1)    # single id returns single instance
60 => <MembershipStatus:0x392a8c8 @attributes={"id"=>"1", "status"=>"Active"}>
61 Membership.find(1,1)  # composite ids returns single instance
62 => <Membership:0x39218b0 @attributes={"user_id"=>"1", "group_id"=>"1"}></pre>
63
64 Using "Ruby on Rails":http://www.rubyonrails.org? You'll want to your url_for helpers
65 to convert composite keys into strings and back again...
66
67 <pre syntax="ruby">Membership.find(:first).to_param # => "1,1"</pre>
68
69 And then use the string id within your controller to find the object again
70
71 <pre syntax="ruby">params[:id] # => '1,1'
72 Membership.find(params[:id])
73 => <Membership:0x3904288 @attributes={"user_id"=>"1", "group_id"=>"1"}></pre>
74
75 That is, an ActiveRecord supporting composite keys behaves transparently
76 throughout your application. Just like a normal ActiveRecord.
77
78
79 h2. Other tricks
80
81 h3. Pass a list of composite ids to the <code>#find</code> method
82
83 <pre syntax="ruby">Membership.find [1,1], [2,1]
84 => [
85   <Membership:0x394ade8 @attributes={"user_id"=>"1", "group_id"=>"1"}>, 
86   <Membership:0x394ada0 @attributes={"user_id"=>"2", "group_id"=>"1"}>
87 ]</pre>
88
89 Perform <code>#count</code> operations
90
91 <pre syntax="ruby">MembershipStatus.find(:first).memberships.count # => 1</pre>
92
93 h3. Routes with Rails
94
95 From Pete Sumskas:
96
97 <blockquote>
98         I ran into one problem that I didn't see mentioned on "this list":http://groups.google.com/group/compositekeys - 
99         and I   didn't see any information about what I should do to address it in the
100         documentation (might have missed it).
101
102         The problem was that the urls being generated for a 'show' action (for
103         example) had a syntax like:
104         
105         <pre>/controller/show/123000,Bu70</pre>
106
107         for a two-field composite PK. The default routing would not match that,
108         so after working out how to do the routing I added:
109         
110         <pre syntax="ruby">map.connect ':controller/:action/:id', :id => /\w+(,\w+)*/</pre>
111         
112         to my <code>route.rb</code> file.
113         
114 </blockquote>
115
116 <a name="dbs"></a>
117
118 h2. Which databases?
119
120
121 A suite of unit tests have been run on the following databases supported by ActiveRecord:
122
123 |_.Database|_.Test Success|_.User feedback|
124 |mysql     |<span class=success>YES</span>|<span class=success>YES</span> ("Yes!":mailto:compositekeys@googlegroups.com?subject=Mysql+is+working or "No...":mailto:compositekeys@googlegroups.com?subject=Mysql+is+failing)|
125 |sqlite3   |<span class=success>YES</span>|<span class=success>YES</span> ("Yes!":mailto:compositekeys@googlegroups.com?subject=Sqlite3+is+working or "No...":mailto:compositekeys@googlegroups.com?subject=Sqlite3+is+failing)|
126 |postgresql|<span class=success>YES</span>|<span class=success>YES</span> ("Yes!":mailto:compositekeys@googlegroups.com?subject=Postgresql+is+working or "No...":mailto:compositekeys@googlegroups.com?subject=Postgresql+is+failing)|
127 |oracle    |<span class=success>YES</span>|<span class=success>YES</span> ("Yes!":mailto:compositekeys@googlegroups.com?subject=Oracle+is+working or "No...":mailto:compositekeys@googlegroups.com?subject=Oracle+is+failing)|
128 |sqlserver |<span class=unknown>???</span> ("I can help":mailto:compositekeys@googlegroups.com?subject=Help+with+SQLServer)|<span class=unknown>???</span> ("Yes!":mailto:compositekeys@googlegroups.com?subject=SQLServer+is+working or "No...":mailto:compositekeys@googlegroups.com?subject=SQLServer+is+failing)|
129 |db2       |<span class=unknown>???</span> ("I can help":mailto:compositekeys@googlegroups.com?subject=Help+with+DB2)|<span class=unknown>???</span> ("Yes!":mailto:compositekeys@googlegroups.com?subject=DB2+is+working or "No...":mailto:compositekeys@googlegroups.com?subject=DB2+is+failing)|
130 |firebird  |<span class=unknown>???</span> ("I can help":mailto:compositekeys@googlegroups.com?subject=Help+with+Firebird)|<span class=unknown>???</span> ("Yes!":mailto:compositekeys@googlegroups.com?subject=Firebird+is+working or "No...":mailto:compositekeys@googlegroups.com?subject=Firebird+is+failing)|
131 |sybase    |<span class=unknown>???</span> ("I can help":mailto:compositekeys@googlegroups.com?subject=Help+with+Sybase)|<span class=unknown>???</span> ("Yes!":mailto:compositekeys@googlegroups.com?subject=Sybase+is+working or "No...":mailto:compositekeys@googlegroups.com?subject=Sybase+is+failing)|
132 |openbase  |<span class=unknown>???</span> ("I can help":mailto:compositekeys@googlegroups.com?subject=Help+with+Openbase)|<span class=unknown>???</span> ("Yes!":mailto:compositekeys@googlegroups.com?subject=Openbase+is+working or "No...":mailto:compositekeys@googlegroups.com?subject=Openbase+is+failing)|
133 |frontbase |<span class=unknown>???</span> ("I can help":mailto:compositekeys@googlegroups.com?subject=Help+with+Frontbase)|<span class=unknown>???</span> ("Yes!":mailto:compositekeys@googlegroups.com?subject=Frontbase+is+working or "No...":mailto:compositekeys@googlegroups.com?subject=Frontbase+is+failing)|
134
135 h2. Dr Nic's Blog
136
137 "http://www.drnicwilliams.com":http://www.drnicwilliams.com - for future announcements and
138 other stories and things.
139
140 h2. Forum
141
142 "http://groups.google.com/group/compositekeys":http://groups.google.com/group/compositekeys
143
144 h2. How to submit patches
145
146 Read the "8 steps for fixing other people's code":http://drnicwilliams.com/2007/06/01/8-steps-for-fixing-other-peoples-code/ and for section "8b: Submit patch to Google Groups":http://drnicwilliams.com/2007/06/01/8-steps-for-fixing-other-peoples-code/#8b-google-groups, use the Google Group above.
147
148
149 The source for this project is available via git. You can "browse and/or fork the source":http://github.com/drnic/composite_primary_keys/tree/master, or to clone the project locally:
150   
151 <pre>git clone git://github.com/drnic/composite_primary_keys.git</pre>
152
153 h2. Licence
154
155 This code is free to use under the terms of the MIT licence. 
156
157 h2. Contact
158
159 Comments are welcome. Send an email to "Dr Nic Williams":mailto:drnicwilliams@gmail.com.