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1 persistence.js
2 ==============
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3 `persistence.js` is a asynchronous Javascript object-relational
4 mapper library. It can be used both in the web browser and on
5 the server using [node.js](http://nodejs.org). It currently
6 supports 4 types of data stores:
7
8 * [HTML5 WebSQL database](http://dev.w3.org/html5/webdatabase/), a
9 somewhat controversial part of HTML5 that is supported in Webkit
10 browsers, specifically on mobile devices, including iPhone, Android
11 and Palm's WebOS.
12 * [Google Gears](http://gears.google.com), a browser plug-in that adds
13 a number of feature to the browser, including a in-browser database.
14 * [MySQL](http://www.mysql.com), using the
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15 [node-mysql](http://github.com/felixge/node-mysql), node.js module
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16 on the server.
17 * In-memory, as a fallback. Keeps the database in memory and is cleaned
18 upon a page refresh (or server restart).
19
20 There is also an experimental support for [Qt 4.7 Declarative UI
21 framework
22 (QML)](http://doc.trolltech.org/4.7-snapshot/declarativeui.html) which
23 is an extension to JavaScript.
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24
25 For browser use, `persistence.js` has no dependencies on any other
26 frameworks, other than the Google Gears [initialization
27 script](http://code.google.com/apis/gears/gears_init.js), in case you
28 want to enable Gears support.
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29
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30 Plug-ins
31 --------
32
33 There are a few `persistence.js` plug-ins available that add functionality:
34
35 * `persistence.search.js`, adds simple full-text search capabilities,
36 see `docs/search.md` for more information.
37 * `persistence.migrations.js`, supports data migrations (changes to
38 the database schema), see `docs/migrations.md` for more information.
39 * `persistence.sync.js`, supports database synchronization with a
40 remote server, see `docs/sync.md` for more information.
41
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42 A Brief Intro to Async Programming
43 ----------------------------------
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44
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45 In browsers, Javascript and the web page's rendering engine share
46 a single thread. The result of this is that only one thing can happen
47 at a time. If a database query would be performed _synchronously_,
48 like in many other programming environments like Java and PHP the
49 browser would freeze from the moment the query was issued until the
50 results came back. Therefore, many APIs in Javascript are defined as
51 _asynchronous_ APIs, which mean that they do not block when an
52 "expensive" computation is performed, but instead provide the call
53 with a function that will be invoked once the result is known. In the
54 meantime, the browser can perform other duties.
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55
56 For instance, a synchronous database call call would look as follows:
57
58 var results = db.query("SELECT * FROM Table");
59 for(...) { ... }
60
61 The execution of the first statement could take half a second, during
62 which the browser doesn't do anything else. By contrast, the
63 asynchronous version looks as follows:
64
65 db.query("SELECT * FROM Table", function(results) {
66 for(...) { ... }
67 });
68
69 Note that there will be a delay between the `db.query` call and the
70 result being available and that while the database is processing the
71 query, the execution of the Javascript continues. To make this clear,
72 consider the following program:
73
74 db.query("SELECT * FROM Table", function(results) {
75 console.log("hello");
76 });
77 console.log("world");
78
79 Although one could assume this would print "hello", followed by
80 "world", the result will likely be that "world" is printed before
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81 "hello", because "hello" is only printed when the results from the
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82 query are available. This is a tricky thing about asynchronous
83 programming that a Javascript developer will have to get used to.
84
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85 Using persistence.js in the browser
86 ===================================
87
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88 Browser support
89 ---------------
90
91 * Modern webkit browsers (Google Chrome and Safari)
92 * Firefox (through Google Gears)
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93 * Android browser (tested on 1.6 and 2.x)
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94 * iPhone browser (iPhone OS 3+)
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95 * Palm WebOS (tested on 1.4.0)
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96
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97 (The following is being worked on:)
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98 Internet Explorer is likely not supported (untested) because it
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99 lacks `__defineGetter__` and `__defineSetter__` support, which
100 `persistence.js` uses heavily. This may change in IE 8.
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101
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102 Setting up
103 ----------
104
105 To use `persistence.js` you need to clone the git repository:
106
107 git clone git://github.com/zefhemel/persistencejs.git
108
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109 To use it you need to copy `lib/persistence.js` to your web directory,
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110 as well as any data stores you want to use. Note that the `mysql` and
111 `websql` stores both depend on the `sql` store. A typical setup
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112 requires you to copy at least `lib/persistence.js`,
113 `lib/persistence.store.sql.js` and `lib/persistence.store.websql.js` to your
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114 web directory. You can then load them as follows:
115
116 <script src="persistence.js" type="application/javascript"></script>
117 <script src="persistence.store.sql.js" type="application/javascript"></script>
118 <script src="persistence.store.websql.js" type="application/javascript"></script>
119
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120
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121 Setup your database
122 -------------------
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123
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124 You need to explicitly configure the data store you want to use,
125 configuration of the data store is store-specific. The WebSQL store
126 (which includes Google Gears support) is configured as follows:
127
128 persistence.store.websql.config(persistence, 'yourdbname', 'A database description', 5 * 1024 * 1024);
129
130 The first argument is always supposed to be `persistence`. The second
131 in your database name (it will create it if it does not already exist,
132 the third is a description for you database, the last argument is the
133 maximum size of your database in bytes (5MB in this example).
134
135 If you're using the in-memory store, you can configure it as follows:
136
137 persistence.store.memory.config(persistence);
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138
139 Schema definition
140 -----------------
141
142 A data model is declared using `persistence.define`. The following two
143 definitions define a `Task` and `Category` entity with a few simple
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144 properties. The property types are based on [SQLite
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145 types](http://www.sqlite.org/datatype3.html), specifically supported
146 types are (but any SQLite type is supported):
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147
148 * `TEXT`: for textual data
149 * `INT`: for numeric values
150 * `BOOL`: for boolean values (`true` or `false`)
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151 * `DATE`: for date/time value (with precision of 1 second)
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152 * `JSON`: a special type that can be used to store arbitrary
153 [JSON](http://www.json.org) data. Note that this data can not be used
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154 to filter or sort in any sensible way. If internal changes are made to a `JSON`
155 property, `persistence.js` may not register them. Therefore, a manual
156 call to `anObj.markDirty('jsonPropertyName')` is required before calling
157 `persistence.flush`.
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158
159 Example use:
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160
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161 var Task = persistence.define('Task', {
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162 name: "TEXT",
163 description: "TEXT",
164 done: "BOOL"
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165 });
166
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167 var Category = persistence.define('Category', {
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168 name: "TEXT",
169 metaData: "JSON"
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170 });
171
172 var Tag = persistence.define('Task', {
173 name: "TEXT"
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174 });
175
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176 The returned values are constructor functions and can be used to
177 create new instances of these entities later:
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178
179
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180 Relationships between entities are defined using the constructor
181 function's `hasMany` call:
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182
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183 // This defines a one-to-many relationship:
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184 Category.hasMany('tasks', Task, 'category');
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185 // These two definitions define a many-to-many relationship
186 Task.hasMany('tags', Tag, 'tasks');
187 Tag.hasMany('tasks', Task, 'tags');
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188
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189 The first statement defines a `tasks` relationship on category objects
190 containing a `QueryCollection` (see the section on query collections
191 later) of `Task`s, it also defines an inverse relationship on `Task`
192 objects with the name `category`. The last two statements define a
193 many-to-many relationships between `Task` and `Tag`. `Task` gets a
194 `tags` property (a `QueryCollection`) containing all its tags and vice
195 versa, `Tag` gets a `tasks` property containing all of its tasks.
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196
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197 The defined entity definitions are synchronized (activated) with the
198 database using a `persistence.schemaSync` call, which takes a callback
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199 function (with a newly created transaction as an argument), that is called
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200 when the schema synchronization has completed, the callback is
201 optional.
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202
203 persistence.schemaSync();
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204 // or
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205 persistence.schemaSync(function(tx) {
206 // tx is the transaction object of the transaction that was
207 // automatically started
208 });
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209
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210 There is also a migrations plugin you can check out, documentation can be found
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211 in [persistence.migrations.docs.md](migrations/persistence.migrations.docs.md) file.
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212
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213 Creating and manipulating objects
214 ---------------------------------
215
216 New objects can be instantiated with the constructor functions.
217 Optionally, an object with initial property values can be passed as
218 well, or the properties may be set later:
219
220 var task = new Task();
221 var category = new Category({name: "My category"});
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222 category.metaData = {rating: 5};
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223 var tag = new Tag();
224 tag.name = "work";
225
226 Many-to-one relationships are accessed using their specified name, e.g.:
227 task.category = category;
228
229 One-to-many and many-to-many relationships are access and manipulated
230 through the `QueryCollection` API that will be discussed later:
231
232 task.tags.add(tag);
233 tasks.tags.remove(tag)l
234 tasks.tags.list(tx, function(allTags) { console.log(allTags); });
235
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236 Persisting/removing objects
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237 ---------------------------
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238
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239 Similar to [hibernate](http://www.hibernate.org), `persistence.js`
240 uses a tracking mechanism to determine which objects' changes have to
241 be persisted to the datase. All objects retrieved from the database
242 are automatically tracked for changes. New entities can be tracked to
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243 be persisted using the `persistence.add` function:
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244
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245 var c = new Category({name: "Main category"});
246 persistence.add(c);
247 for ( var i = 0; i < 5; i++) {
248 var t = new Task();
249 t.name = 'Task ' + i;
250 t.done = i % 2 == 0;
251 t.category = c;
252 persistence.add(t);
253 }
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254
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255 Objects can also be removed from the database:
256
257 persistence.remove(c);
258
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259 All changes made to tracked objects can be flushed to the database by
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260 using `persistence.flush`, which takes a transaction object and
261 callback function as arguments. A new transaction can be started using
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262 `persistence.transaction`:
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263
264 persistence.transaction(function(tx) {
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265 persistence.flush(tx, function() {
266 alert('Done flushing!');
267 });
268 });
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269
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270 For convenience, it is also possible to not specify a transaction or
271 callback, in that case a new transaction will be started
272 automatically. For instance:
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273
274 persistence.flush();
275 // or, with callback
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276 persistence.flush(function() {
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277 alert('Done flushing');
278 });
279
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280 Note that when no callback is defined, the flushing still happens
281 asynchronously.
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282
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283 __Important__: Changes and new objects will not be persisted until you
284 explicitly call `persistence.flush()`. The exception to this rule is
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285 using the `list(...)` method on a database `QueryCollection`, which also
286 flushes first, although this behavior may change in the future.
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287
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288 Dumping and restoring data
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289 --------------------------
290
291 The library supports two kinds of dumping and restoring data.
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292
293 `persistence.dump` can be used to create an object containing a full
294 dump of a database. Naturally, it is adviced to only do this with
295 smaller databases. Example:
296
297 persistence.dump(tx, [Task, Category], function(dump) {
298 console.log(dump);
299 });
300
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301 The `tx` is left out, a new transaction will be started for the
302 operation. If the second argument is left out, `dump` defaults
303 to dumping _all_ defined entities.
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304
305 The dump format is:
306
307 {"entity-name": [list of instances],
308 ...}
309
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310 `persistence.load` is used to restore the dump produced by
311 `persistence.dump`. Usage:
312
313 persistence.load(tx, dumpObj, function() {
314 alert('Dump restored!');
315 });
316
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317 The `tx` argument can be left out to automatically start a new
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318 transaction. Note that `persistence.load` does not empty the database
319 first, it simply attempts to add all objects to the database. If
320 objects with, e.g. the same ID already exist, this will fail.
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321
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322 Similarly, `persistence.loadFromJson` and `persistence.dumpToJson`
323 respectively load and dump all the database's data as JSON strings.
324
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325 Entity constructor functions
326 ----------------------------
327
328 The constructor function returned by a `persistence.define` call
329 cannot only be used to instantiate new objects, it also has some
330 useful methods of its own:
331
332 * `EntityName.all([session])` returns a query collection containing
333 all
334 persisted instances of that object. The `session` argument is
335 optional and only required when `persistence.js` is used in
336 multi-session mode.
337 * `EntityName.load([session], [tx], id, callback)` loads an particular
338 object from the database by id or returns `null` if it has not been
339 found.
340 * `EntityName.findBy([session], [tx], property, value, callback)` searches
341 for a particular object based on a property value (this is assumed to
342 be unique), the callback function is called with the found object or
343 `null` if it has not been found.
344
345 And of course the methods to define relationships to other entities:
346
347 * `EntityName.hasMany(property, Entity, inverseProperty)` defines a
348 1:N or N:M relationship (depending on the inverse property)
349 * `EntityName.hasOne(property, Entity)` defines a 1:1 or N:1
350 relationship
351
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352
353 Entity objects
354 --------------
355
356 Entity instances also have a few predefined properties and methods you
357 should be aware of:
358
359 * `obj.id`, contains the identifier of your entity, this is a
360 automatically generated (approximation of a) UUID. You should
361 never write to this property.
362 * `obj.fetch(prop, callback)`, if an object has a `hasOne`
363 relationship to another which has not yet been fetched from the
364 database (e.g. when `prefetch` wasn't used), you can fetch in manually
365 using `fetch`. When the property object is retrieved the callback function
366 is invoked with the result, the result is also cached in the entity
367 object itself.
368 * `obj.selectJSON([tx], propertySpec, callback)`, sometime you need to extract
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369 a subset of data from an entity. You for instance need to post a
370 JSON representation of your entity, but do not want to include all
371 properties. `selectJSON` allows you to do that. The `propertySpec`
372 arguments expects an array with property names. Some examples:
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373 * `['id', 'name']`, will return an object with the id and name property of this entity
374 * `['*']`, will return an object with all the properties of this entity, not recursive
375 * `['project.name']`, will return an object with a project property which has a name
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376 property containing the project name (hasOne relationship)
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377 * `['project.[id, name]']`, will return an object with a project property which has an
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378 id and name property containing the project name (hasOne relationship)
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379 * `['tags.name']`, will return an object with an array `tags` property containing
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380 objects each with a single property: name
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381
382
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383 Query collections
384 -----------------
385
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386 A core concept of `persistence.js` is the `QueryCollection`. A
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387 `QueryCollection` represents a (sometimes) virtual collection that can
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388 be filtered, ordered or paginated. `QueryCollection`s are somewhate
389 inspired by [Google AppEngine's Query
390 class](http://code.google.com/appengine/docs/python/datastore/queryclass.html).
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391 A `QueryCollection` has the following methods:
392
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393 * `filter(property, operator, value)`
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394 Returns a new `QueryCollection` that adds a filter, filtering a
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395 certain property based on an operator and value. Supported operators
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396 are '=', '!=', '<', '<=', '>', '>=', 'in' and 'not in'. Example:
397 `.filter('done', '=', true)`
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398 * `order(property, ascending)`
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399 Returns a new `QueryCollection` that will order its results by the
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400 property specified in either an ascending (ascending === true) or
401 descending (ascending === false) order.
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402 * `limit(n)`
403 Returns a new `QueryCollection` that limits the size of the result
404 set to `n` items. Useful for pagination.
405 * `skip(n)`
406 Returns a new `QueryCollection` that skips the first `n` results.
407 Useful for pagination.
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408 * `prefetch(rel)`
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409 Returns a new `QueryCollection` that prefetches entities linked
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410 through relationship `rel`, note that this only works for one-to-one
411 and many-to-one relationships.
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412 * `add(obj)`
413 Adds object `obj` to the collection.
414 * `remove(obj)`
415 Removes object `obj` from the collection.
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416 * `list([tx], callback)`
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417 Asynchronously fetches the results matching the formulated query.
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418 Once retrieved, the callback function is invoked with an array of
419 entity objects as argument.
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420 * `each([tx], eachCallback)`
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421 Asynchronously fetches the results matching the formulated query.
422 Once retrieved, the `eachCallback` function is invoked on each
423 element of the result objects.
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424 * `forEach([tx], eachCallback)`
425 Alias for `each`
426 * `one([tx], callback)`
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427 Asynchronously fetches the first element of the collection, or `null` if none.
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428 * `destroyAll([tx], callback)`
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429 Asynchronously removes all the items in the collection. __Important__: this does
430 not only remove the items from the collection, but removes the items themselves!
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431 * `count([tx], callback)`
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432 Asynchronously counts the number of items in the collection. The arguments passed
433 to the `callback` function is the number of items.
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434
435 Query collections are returned by:
436
437 * `EntityName.all()`, e.g. `Task.all()`
438 * one-to-many and many-to-many relationships, e.g. `task.tags`
439
440 Example:
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441
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442 var allTasks = Task.all().filter("done", '=', true).prefetch("category").order("name", false).limit(10);
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443
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444 allTasks.list(null, function (results) {
445 results.forEach(function (r) {
446 console.log(r.name)
447 window.task = r;
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448 });
449 });
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450
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451 Using persistence.js on the server
452 ==================================
453
dd1c7c4 @zefhemel Set-up library to be used a node library installable via npm. In fact,
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454 Installing `persistence.js` on node is easy using [npm](http://npmjs.org):
455
456 npm install persistencejs
457
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458 Sadly the node.js server environment requires slight changes to
459 `persistence.js` to make it work with multiple database connections:
460
461 * A `Session` object needs to be passed as an extra argument to
462 certain method calls, typically as a first argument.
463 * Methods previously called on the `persistence` object itself are now
464 called on the `Session` object.
465
466 An example `node.js` application is included in `test/node-blog.js`.
467
468 Setup
469 -----
470 You need to `require` two modules, the `persistence.js` library itself
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471 and the MySQL backend module.
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472
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473 var persistence = require('persistencejs/persistence').persistence;
474 var persistenceStore = require('persistencejs/persistence.store.mysql');
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475
476 Then, you configure the database settings to use:
477
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478 persistenceStore.config(persistence, 'localhost', 3306, 'dbname', 'username', 'password');
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479
480 Subsequently, for every connection you handle (assuming you're
481 building a sever), you call the `persistenceStore.getSession()`
482 method:
483
484 var session = persistenceBackend.getSession();
485
486 This session is what you pass around, typically together with a
487 transaction object. Note that currently you can only have one
488 transaction open per session and transactions cannot be nested.
489
490 session.transaction(function(tx) {
491 ...
492 });
493
494 Defining your data model
495 ------------------------
496
497 Defining your data model is done in exactly the same way as regular `persistence.js`:
498
499 var Task = persistence.define('Task', {
500 name: "TEXT",
501 description: "TEXT",
502 done: "BOOL"
503 });
504
505 A `schemaSync` is typically performed as follows:
506
507 session.schemaSync(tx, function() {
508 ...
509 });
510
511 Creating and manipulating objects
512 ---------------------------------
513
514 Creating and manipulating objects is done much the same way as with
515 regular `persistence.js`, except that in the entity's constructor you
516 need to reference the `Session` again:
517
518 var t = new Task(session);
519 ...
520 session.add(t);
521
522 session.flush(tx, function() {
523 ...
524 });
525
526 Query collections
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527 -----------------
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528
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529 Query collections work the same way as in regular `persistence.js`
530 with the exception of the `Entity.all()` method that now also requires
531 a `Session` to be passed to it:
532
533 Task.all(session).filter('done', '=', true).list(tx, function(tasks) {
534 ...
535 });
536
537 Closing the session
538 -------------------
539
540 After usage, you need to close your session:
541
542 session.close();
543
544 Bugs and Contributions
545 ======================
546
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547 If you find a bug, please [report it](http://yellowgrass.org/project/persistence.js).
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548 or fork the project, fix the problem and send me a pull request. For
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549 a list of planned features and open issues, have a look at the [issue
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550 tracker](http://yellowgrass.org/project/persistence.js).
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551
0302c86 Added link to Google Group
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552 For support and discussion, please join the [persistence.js Google
553 Group](http://groups.google.com/group/persistencejs).
554
0e32d43 @zefhemel Added AUTHORS file
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555 Thanks goes to the people listed in `AUTHORS` for their contributions.
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556
cda1de2 @zefhemel Added link to the persistence.js GWT wrapper.
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557 If you use [GWT](http://code.google.com/webtoolkit/) (the Google Web
558 Toolkit), be sure to have a look at [Dennis Z. Jiang's GWT persistence.js
559 wrapper](http://github.com/dennisjzh/gwt-persistence).
560
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561 License
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562 =======
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563
564 This work is licensed under the [MIT license](http://en.wikipedia.org/wiki/MIT_License).
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565
566 Support this work
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567 -----------------
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568
569 You can support this project by flattering it:
570
571 <a href="http://flattr.com/thing/2510/persistence-js" target="_blank">
572 <img src="http://api.flattr.com/button/button-static-50x60.png" title="Flattr this" border="0" /></a>
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