第五章 MongoDb索引优化 5.4

5、唯一索引

先看看之前创建的，rsc索引：

index ---------

{ "name" : "rsc_1" , "ns" : "ms_basic.schedule" , "key" : { "rsc" : 1}}

在rsc字段上，创建唯一索引：

coll.dropIndex(new BasicDBObject("rsc", 1));

coll.ensureIndex(new BasicDBObject("rsc", 1).append("unique", true));

显示结果：

index ---------

{ "name" : "rsc_1_unique_" , "ns" : "ms_basic.schedule" , "key" : { "rsc" : 1 , "unique" : true}}

存在如下rsc=的数据：

{ "_id" : { "$oid" : "4c2fe764dd969674cb31a0be"} , "liveStatus" : 0 , "startDate" : "2010-11-12" , "isList" : 0 , "location" : "CAG" , "posttime" : "2010-04-01 15:04:57.0" , "rsc" : "WRM160513" , "noliveTvName" : "" , "endDate" : "2010-11-12" , "endTime" : "09:30" , "isGold" : 0 , "version" : 0 , "startTime" : "09:30" , "disciplineName" : "摔跤" , "event" : "160" , "gender" : "M" , "isMedal" : 0 , "discipline" : "WR" , "venueId" : "CAG" , "phaseName" : "资格赛" , "isRecommend" : 0 , "isData" : 0 , "eventUnitType" : "HATH" , "chatroomStatus" : 0 , "isChina" : 0 , "isStartTime" : 0 , "competitionStatus" : 0 , "unit" : "13" , "tvName" : "男子古典式 - 60公斤级资格赛" , "flag" : 0 , "scheduleName" : "资格赛" , "isEndTime" : 0 , "rid" : "" , "eventName" : "男子古典式 - 60公斤级" , "phase" : "5" , "isResult" : 0}

往表data中插入一条记录。

System.out.println("-----------华丽分隔线---------------");

Schedule schedule = new Schedule();

schedule.setRsc("WRM160513");

schedule.setScheduleName("重复值");

BasicDBObject val = new BasicDBObject();

val.put("rsc","WRM160513");

val.put("scheuleName","kaokao");

coll.insert(val);

没有报错，查询结果：

{ "_id" : { "$oid" : "4c2fe764dd969674cb31a0be"} , "liveStatus" : 0 , "startDate" : "2010-11-12" , "isList" : 0 , "location" : "CAG" , "posttime" : "2010-04-01 15:04:57.0" , "rsc" : "WRM160513" , "noliveTvName" : "" , "endDate" : "2010-11-12" , "endTime" : "09:30" , "isGold" : 0 , "version" : 0 , "startTime" : "09:30" , "disciplineName" : "摔跤" , "event" : "160" , "gender" : "M" , "isMedal" : 0 , "discipline" : "WR" , "venueId" : "CAG" , "phaseName" : "资格赛" , "isRecommend" : 0 , "isData" : 0 , "eventUnitType" : "HATH" , "chatroomStatus" : 0 , "isChina" : 0 , "isStartTime" : 0 , "competitionStatus" : 0 , "unit" : "13" , "tvName" : "男子古典式 - 60公斤级资格赛" , "flag" : 0 , "scheduleName" : "资格赛" , "isEndTime" : 0 , "rid" : "" , "eventName" : "男子古典式 - 60公斤级" , "phase" : "5" , "isResult" : 0}

注意：java应用中，有个问题，如果数据已经重复了，那么使用：

coll.ensureIndex(new BasicDBObject("rsc", 1).append("unique", true));

是没有错误提示的，此时继续执行插入操作，是成功的。

{ "_id" : { "$oid" : "4c2fe764dd969674cb31a0be"} , "liveStatus" : 0 , "startDate" : "2010-11-12" , "isList" : 0 , "location" : "CAG" , "posttime" : "2010-04-01 15:04:57.0" , "rsc" : "WRM160513" , "noliveTvName" : "" , "endDate" : "2010-11-12" , "endTime" : "09:30" , "isGold" : 0 , "version" : 0 , "startTime" : "09:30" , "disciplineName" : "摔跤" , "event" : "160" , "gender" : "M" , "isMedal" : 0 , "discipline" : "WR" , "venueId" : "CAG" , "phaseName" : "资格赛" , "isRecommend" : 0 , "isData" : 0 , "eventUnitType" : "HATH" , "chatroomStatus" : 0 , "isChina" : 0 , "isStartTime" : 0 , "competitionStatus" : 0 , "unit" : "13" , "tvName" : "男子古典式 - 60公斤级资格赛" , "flag" : 0 , "scheduleName" : "资格赛" , "isEndTime" : 0 , "rid" : "" , "eventName" : "男子古典式 - 60公斤级" , "phase" : "5" , "isResult" : 0}

{ "_id" : { "$oid" : "4c3334ea76c7eebe35fb1f81"} , "rsc" : "WRM160513" , "scheduleName" : "kaokao"}

java中，生成索引结果：

> db.schedule.getIndexes();

[

{

"name" : "_id_",

"ns" : "ms_basic.schedule",

"key" : {

"_id" : 1

}

},

{

"name" : "rsc_1_unique_",

"ns" : "ms_basic.schedule",

"key" : {

"rsc" : 1,

"unique" : true

}

}

]

命令行结果：

> db.schedule.ensureIndex({rsc:1},{unique: true});

> db.schedule.getIndexes();

[

{

"name" : "_id_",

"ns" : "ms_basic.schedule",

"key" : {

"_id" : 1

}

},

{

"_id" : ObjectId("4c3335de22090000000065d5"),

"ns" : "ms_basic.schedule",

"key" : {

"rsc" : 1

},

"name" : "rsc_1",

"unique" : true

}

]

后来检查发现：

应该使用：coll.ensureIndex(new BasicDBObject("rsc", 1),"rsc",true);

而不是：coll.ensureIndex(new BasicDBObject("rsc", 1).append("unique", true));

这种方式相当于创建了组合索引：rsc_unique，是错误的

认真看看API文档说明即可发现。

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