PouchDB 基础

GUIDES

http://pouchdb.com/guides/

1.建立couchDB环境

• 下载并安装CouchDB：
  
  
  https://couchdb.apache.org/#download

• 测试：

  • 于CMD下，执行 curl localhost:5984
  • 打开 http://localhost:5984/_utils/fauxton/ 或 http://localhost:5984/_utils/ 以进入 CouchDB界面

• Set _utilsp CORS （用于跨域）

  • 安装：于CMD下，执行 npm install -g add-cors-to-couchdb
  • 运行：于CMD下，执行 add-cors-to-couchdb

2.建立PouchDB环境

• 下载
  • https://pouchdb.com/download.html
• 在html页面引入
  • <script src="pouchdb-3.4.0.min.js"></script>

3.使用pouchdb数据库

本地数据库

	//创建数据库:
	var db = new PouchDB('kittens');

远程数据库

	//创建数据库:
	var db = new PouchDB('http://localhost:5984/kittens');

打开http://localhost:5984/kittens可以预览数据库信息

地址解析:
	http://     localhost:5984     /kittens
	|_____|     |____________|      |_____|
	   |              |                |
	Protocol     Where CouchDB       database
	(https if    itself is           name
	Cloudant)    hosted

使用info获取数据库信息

	db.info().then(function (info) {
	  console.log(info);
	})

删除本地的所有数据库（Chrome）

• 使用ClearBrowserData
• 清除浏览器缓存

4.使用文档数据

文档数据结构：

	SQL concept			PouchDB concept
	table		<=>		no equivalent(不存在表格)
	row			<=>		document(相当于doc)
	column		<=>		field（值域）
	primary 	<=>		key	primary key (_id)
	index		<=>		view

定义一个doc结构对象，*doc对象必须要有_id属性

	var doc = {
	  "_id": "mittens",
	  "name": "Mittens",
	  "occupation": "kitten",
	  "age": 3,
	  "hobbies": [
	    "playing with balls of yarn",
	    "chasing laser pointers",
	    "lookin' hella cute"
	  ]
	};

使用put方法存储到数据库

	db.put(doc);

获取数据:（根据_id获取）

	db.get('mittens').then(function (doc) {
	  console.log(doc);
	});

数据版本 (_rev)

_rev:

• 版本标志位
• 操作数据时，需要设置该属性

更新数据方法:

手动设置该属性

	doc.age = 4;
	doc._rev = "1-bea5fa18e06522d12026f4aee6b15ee4";//（传入当前的_rev属性）
	db.put(doc);

获取当前数据，此时即包含_rev属性

	db.get('mittens').then(function (doc) {
	  // update his age
	  doc.age = 4;
	  // put him back
	  return db.put(doc);
	}).then(function () {
	  // fetch mittens again
	  return db.get('mittens');
	}).then(function (doc) {
	  console.log(doc);
	});

更新数据时，需要传入当前的_rev属性，若不输入_rev属性，会报错如下：

	{
	  "status": 409,
	  "name": "conflict",
	  "message": "Document update conflict"
	}

5.异步处理数据

callback:

	db.get('mittens', function (error, doc) {
	  if (error) {
	    // oh noes! we got an error
	  } else {
	    // okay, doc contains our document
	  }
	});

promises:

	db.get('charlie').then(function (charlie) {
	  // Within this function, you can do
	  // try/catch/return like you normally would,
	  // and it will be handled asynchronously!
	}).then(function (result) {
	  // If the previous function returned something
	  // (or returned undefined), it will show up here
	  // as "result".
	}).catch(function (err) {
	  // If the previous function threw an error,
	  // it will show up here as "err".
	});

6.更新删除数据

创建一个默认的doc（若存在则获取，不存在则创建）

	db.get('config').catch(function (err) {
	  if (err.status === 404) { // not found!
	    return {
	      _id: 'config',
	      background: 'blue',
	      foreground: 'white',
	      sparkly: 'false'
	    };
	  } else { // hm, some other error
	    throw err;
	  }
	}).then(function (configDoc) {
	  // sweet, here is our configDoc
	}).catch(function (err) {
	  // handle any errors
	});

删除数据

When you remove() a document, it's not really deleted; it just gets a _deleted attribute added to it)

	//1)直接remove doc
	db.get('mydoc').then(function (doc) {
	  return db.remove(doc);
	});

	//2) 使用_id,_rev
	db.get('mydoc').then(function (doc) {
	  return db.remove(doc._id, doc._rev);
	});

	//3) 将_deleted字段设为true
	db.get('mydoc').then(function (doc) {
	  doc._deleted = true;
	  return db.put(doc);
	});

7.Bulk operations (批量操作)

bulkDocs():(批量插入)

	db.bulkDocs([
	  {
	    _id: 'mittens',
	    occupation: 'kitten',
	    cuteness: 9.0
	  },
	  {
	    _id: 'katie',
	    occupation: 'kitten',
	    cuteness: 7.0
	  },
	  {
	    _id: 'felix',
	    occupation: 'kitten',
	    cuteness: 8.0
	  }
	]);

allDocs() 批量查询

	db.put({
	    _id: new Date().toJSON(),
	    name: 'Mittens',
	    occupation: 'kitten',
	    cuteness: 9.0
	}).then(function () {
	  return db.put({
	    _id: new Date().toJSON(),
	    name: 'Katie',
	    occupation: 'kitten',
	    cuteness: 7.0
	  });
	}).then(function () {
	  return db.put({
	    _id: new Date().toJSON(),
	    name: 'Felix',
	    occupation: 'kitten',
	    cuteness: 8.0
	  });
	]).then(function () {
	  return db.allDocs({include_docs: true});
	}).then(function (response) {
	  console.log(response);
	}).catch(function (err) {
	  console.log(err);
	});

8.使用 attachments

base64:

	btoa('hello world')      <=> "aGVsbG8gd29ybGQ="
	atob('aGVsbG8gd29ybGQ=') <=> "hello world"

Image attachments

	db.put({
	  _id: 'meowth',
	  _attachments: {
	    'meowth.png': {
	      content_type: 'image/png',
	      data: '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'
	    }
	  }
	}).then(function () {
	  return db.getAttachment('meowth', 'meowth.png');
	}).then(function (blob) {
	  var url = URL.createObjectURL(blob);
	  var img = document.createElement('img');
	  img.src = url;
	  document.body.appendChild(img);
	}).catch(function (err) {
	  console.log(err);
	});

9.Replication(同步/拷贝 数据)

1.创建本地数据库

	var localDB = new PouchDB('mylocaldb')

2.创建要要远程的数据库

	var remoteDB = new PouchDB('http://localhost:5984/myremotedb')

3.同步本地数据库到远程的数据库

	localDB.replicate.to(remoteDB).on('complete', function () {
	  // yay, we're done!
	}).on('error', function (err) {
	  // boo, something went wrong!
	});

4.双向复制

	localDB.replicate.to(remoteDB);
	localDB.replicate.from(remoteDB);

or

	localDB.sync(remoteDB);

	localDB.sync(remoteDB).on('complete', function () {
	  // yay, we're in sync!
	}).on('error', function (err) {
	  // boo, we hit an error!
	});

5.同步的应答操作

	//1.To enable live replication, you simply specify {live: true}:
	localDB.sync(remoteDB, {
	  live: true
	}).on('change', function (change) {
	  // yo, something changed!
	}).on('error', function (err) {
	  // yo, we got an error! (maybe the user went offline?)
	})));

	//2.You can allow PouchDB to automatically handle this error, and retry until the connection is re-established, by using the retry option:
	localDB.sync(remoteDB, {
	  live: true,
	  retry: true
	}).on('change', function (change) {
	  // yo, something changed!
	}).on('paused', function (info) {
	  // replication was paused, usually because of a lost connection
	}).on('active', function (info) {
	  // replication was resumed
	}).on('error', function (err) {
	  // totally unhandled error (shouldn't happen)
	})));

6.取消同步

	//1.
	var syncHandler = localDB.sync(remoteDB, {
	  live: true,
	  retry: true
	});

	syncHandler.on('complete', function (info) {
	  // replication was canceled!
	});

	syncHandler.cancel(); // <-- this cancels it

	//2.
	var replicationHandler = localDB.replicate.to(remoteDB, {
	  live: true,
	  retry: true
	});

	replicationHandler.on('complete', function (info) {
	  // replication was canceled!
	});

	replicationHandler.cancel(); // <-- this cancels it

10.Map/reduce queries

临时创建:

	//emit()的内容 是 用于查询时的数据(key对应的字段)
	//此处的意思就是创建一个index,查找doc.name 为 'foo'的所有数据
	db.query(function (doc, emit) {
	  	emit(doc.name);
	}, {key: 'foo'}).then(function (result) {
	 	// found docs with name === 'foo'
	}).catch(function (err) {
	 	// handle any errors
	});

持久性创建:

首先创建一个视图(index)

	//注意 _id 命名规范以   _design/  开头
	var ddoc = {
	  _id: '_design/my_index',
	  	views: {
	  		//以name为查找的属性
		    by_name: {
		     	map: function (doc) {
		     		emit(doc.name);
		     	}.toString()
		    }
  		}
	};
	// save it
	pouch.put(ddoc).then(function () {
	  // success!
	}).catch(function (err) {
	  // some error (maybe a 409, because it already exists?)
	});

然后就可以通过id,视图名直接使用

	//查找name 为test的数据
	db.query('my_index/by_name',{
		key:'test'
	}).then(function (res) {
	  // got the query results
	}).catch(function (err) {
	  // some error
	});

	//第一次使用的时候因为要创建视图会相对慢，可以先实行一个空的查询让其先建立视图
	db.query('my_index/by_name', {
	  limit: 0 // don't return any results
	}).then(function (res) {
	  // index was built!
	}).catch(function (err) {
	  // some error
	});

Map functions

	//Map functions:
	function myMapFunction(doc) {
	  if (doc.type === 'pokemon') {
	    if (doc.name === 'Pikachu') {
	      emit('Pika pi!');
	    } else {
	      emit(doc.name);
	    }
	  }
	}

	// find pokemon with name === 'Pika pi!'
	pouch.query(myMapFunction, {
	  key          : 'Pika pi!',
	  include_docs : true
	}).then(function (result) {
	  // handle result
	}).catch(function (err) {
	  // handle errors
	});

	// find the first 5 pokemon whose name starts with 'P'
	pouch.query(myMapFunction, {
		startkey     : 'P',
		endkey       : 'P\uffff',
		limit        : 5,
		include_docs : true
	}).then(function (result) {
	  // handle result
	}).catch(function (err) {
	  // handle errors
	});

	//Reduce functions:
	// emit the first letter of each pokemon's name
	var myMapReduceFun = {
		map: function (doc) {
			emit(doc.name.charAt(0));
		},
	  reduce: '_count'
	};
	// count the pokemon whose names start with 'P'
	pouch.query(myMapReduceFun, {
	  key: 'P', reduce: true, group: true
	}).then(function (result) {
	  // handle result
	}).catch(function (err) {
	  // handle errors
	});

11.压缩，删除数据库

Compacting a database

return db.compact().then(function (info) {
  // compaction complete
}).catch(function (err) {
  // handle errors
});

Auto-compaction

	var db = new PouchDB('mydb', {auto_compaction: true});

Destroying a database

	PouchDB.destroy('mydb').then(function () {
	  // database destroyed
	}).catch(function (err) {
	  // error occurred
	})