mongodb实践 4
#存入数据
#基于document的数据
*定义一个文档对象@
---
> doc = { author: 'joe',created : new Date('03/28/2009'),title : 'Yet another blog post',text : 'Here is the text...',tags : [ 'example', 'joe' ],comments : [ { author: 'jim', comment: 'I disagree' }, { author: 'nancy', comment: 'Good post' }]} *保存该文档@
> db.posts.insert(doc); *检索该文档@
> db.posts.find({"comments.author":"jim"});{ "_id" : ObjectId("4ee9550cbd3e00000000337e"), "author" : "joe", "created" : "Sat Mar 28 2009 00:00:00 GMT+0800", "title" : "Yet another blog post", "text" : "Here is the text...", "tags" : [ "example", "joe" ], "comments" : [{"author" : "jim","comment" : "I disagree"},{"author" : "nancy","comment" : "Good post"}] }
ps:在使用java driver 的时候，可以通过WriteConcern来返回异常信息，如@
db.test.insert(obj, WriteConcern.SAFE);
#mongodb优化
*使用索引@
db.things.ensureIndex({i:1});
*限制返回数据条数@
db.things.find().sort({i:1}).limit(10);
*只返回需要的列@
db.things.find({},{i2:true}).sort({i:-1}).limit(10); 返回i2域
db.things.find({},{i2:false}).sort({i:-1}).limit(10); 返回除i2的域，即i,i3
db.things.find({},{i2:false,_id:0}).sort({i:-1}).limit(10); 返回除i2、_id的剩余域
*还可以这么写（照搬官网示例）@
db.posts.find({}, {comments:{$slice: 5}}) // first 5 commentsdb.posts.find({}, {comments:{$slice: -5}}) // last 5 commentsdb.posts.find({}, {comments:{$slice: }}) // skip 20, limit 10db.posts.find({}, {comments:{$slice: [-20, 10]}}) // 20 from end, limit 10
*使用mongodb profiler（剖面测量仪，性能监视）@
> db.commandHelp("profile");help for: profile enable or disable performance profiling{ profile : <n> }0=off 1=log slow ops 2=log allhttp://www.mongodb.org/display/DOCS/Database+Profiler> db.setProfilingLevel(2);{ "was" : 0, "slowms" : 100, "ok" : 1 } 首选查一下帮助信息，然后将profillingLevel设置为2，was表示以前的设置。查看当前设置@
> db.getProfilingLevel();2 slowms值>100ms即被认为慢，可以通过如下命令修改默认值@
> db.setProfilingLevel(2,20){ "was" : 2, "slowms" : 20, "ok" : 1 }
*明确的指明需要使用的索引@
> db.things.find({i:4}).hint({i:1});{ "_id" : ObjectId("4ee8510a0c16000000006ec9"), "i" : 4, "i2" : 16 }{ "_id" : ObjectId("4ee8514d0c16000000006edd"), "i" : 4, "i2" : 16, "i3" : 64 }
PS:贴一段使用索引的性能测试代码：（测试环境：window7 64 4G RAM）
import com.mongodb.BasicDBObject;import com.mongodb.DB;import com.mongodb.DBCollection;import com.mongodb.DBCursor;import com.mongodb.DBObject;import com.mongodb.Mongo;import com.mongodb.MongoException;public class PerformanceTest {private Mongo mongo = null;public PerformanceTest() {}private Mongo getInstance() {if (mongo == null)try {mongo = new Mongo();} catch (UnknownHostException e) {e.printStackTrace();} catch (MongoException e) {e.printStackTrace();}return mongo;}/** * 插入简单数据 */public static void Performance() {PerformanceTest pt = new PerformanceTest();Mongo mongo = pt.getInstance();DB db = mongo.getDB("mytest");/*// make a document and insert itBasicDBObject doc = new BasicDBObject();doc.put("name", "MongoDB");doc.put("type", "database");doc.put("count", 1);BasicDBObject info = new BasicDBObject();info.put("x", 203);info.put("y", 102);doc.put("info", info);Set<String> colls = db.getCollectionNames();for (String s : colls) {System.out.println(s);}*/DBCollection coll = db.getCollection("testCollection");int i = 0;DBObject myDoc = coll.findOne();//System.out.println(myDoc);for (i = 0; i < 6000000; i++) {coll.insert(new BasicDBObject().append("i", i).append("j", i).append("k", i));}/*DBCursor cur = coll.find();while (cur.hasNext()) {System.out.println(cur.next());}coll.drop();*/System.out.println(coll.count());}public static void creatIndex(){PerformanceTest pt = new PerformanceTest();Mongo mongo = pt.getInstance();DB db = mongo.getDB("mytest");DBCollection coll = db.getCollection("testCollection");coll.createIndex(new BasicDBObject("i", 1));}public static void query(){PerformanceTest pt = new PerformanceTest();Mongo mongo = pt.getInstance();DB db = mongo.getDB("mytest");BasicDBObject query = new BasicDBObject(); query.put("i", new BasicDBObject("$gt", 1234).append("$lte", 1240));// i.e. 20 < i <= 30 DBCollection coll = db.getCollection("testCollection"); DBCursor cur = coll.find(query); while(cur.hasNext()) { System.out.println(cur.next()); }}public static void main(String[] args) {Long cost = System.currentTimeMillis();PerformanceTest pt = new PerformanceTest();Mongo mongo = pt.getInstance();DB db = mongo.getDB("mytest");DBCollection coll = db.getCollection("testCollection");System.out.println("count:"+coll.count());System.out.println(Integer.MAX_VALUE);System.out.println(Long.MAX_VALUE);//创建索引后，效率有大幅度的提升，6000000条数据(仅有一列)没有索引时查询耗时2865毫秒，//创建索引后，查询耗时111毫秒。//creatIndex();query();//Performance();cost = System.currentTimeMillis() - cost;System.out.println("cost:"+cost);/*coll.dropIndexes();coll.drop();db.dropDatabase();*/}}
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