提升数据库检索性能的手段
通过getIndexes()来获取已经存在的索引内容
db.students.getIndexes();
/* 1 */[ { "v" : 1, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "mldn.students" }] 创建自己的索引
范例：创建一个索引，在age列加一个将序索引
db.students.ensureIndex({"age":-1}); /* 1 */[ { "v" : 1, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "mldn.students" }, { "v" : 1, "key" : { "age" : -1.0 }, "name" : "age_-1", "ns" : "mldn.students" }] 使用解释来分析索引
db.students.find({"age":19}).explain(); /* 1 */{ "queryPlanner" : { "plannerVersion" : 1, "namespace" : "mldn.students", "indexFilterSet" : false, "parsedQuery" : { "age" : { "$eq" : 19.0 } }, "winningPlan" : { "stage" : "FETCH", "inputStage" : { "stage" : "IXSCAN", "keyPattern" : { "age" : -1.0 }, "indexName" : "age_-1", "isMultiKey" : false, "isUnique" : false, "isSparse" : false, "isPartial" : false, "indexVersion" : 1, "direction" : "forward", "indexBounds" : { "age" : [ "[19.0, 19.0]" ] } } }, "rejectedPlans" : [] }, "serverInfo" : { "host" : "jiqing", "port" : 27017, "version" : "3.2.17-25-gae6f04a", "gitVersion" : "ae6f04a7cd143132fb3185669a8abc5d7c4ab3cc" }, "ok" : 1.0} 再分析一个没有索引的成员
db.students.find({"score":{"$gt":80}}).explain(); /* 1 */{ "queryPlanner" : { "plannerVersion" : 1, "namespace" : "mldn.students", "indexFilterSet" : false, "parsedQuery" : { "score" : { "$gt" : 80.0 } }, "winningPlan" : { "stage" : "COLLSCAN", "filter" : { "score" : { "$gt" : 80.0 } }, "direction" : "forward" }, "rejectedPlans" : [] }, "serverInfo" : { "host" : "jiqing", "port" : 27017, "version" : "3.2.17-25-gae6f04a", "gitVersion" : "ae6f04a7cd143132fb3185669a8abc5d7c4ab3cc" }, "ok" : 1.0} 有索引和没索引的成员一起使用呢？
db.students.find({"$and":[ {"age":{"$gt":19}}, {"score":{"$gt":80}} ]}).explain(); and的时候用到了索引，or的时候没有用到。
可以定义复合索引
db.students.ensureIndex({"age":-1,"score":-1},{"name":"age_score_index"}); /* 1 */[ { "v" : 1, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "mldn.students" }, { "v" : 1, "key" : { "age" : -1.0 }, "name" : "age_-1", "ns" : "mldn.students" }, { "v" : 1, "key" : { "age" : -1.0, "score" : -1.0 }, "name" : "age_score_index", "ns" : "mldn.students" }] 强制使用索引
db.students.find({"$or":[ {"age":{"$gt":19}}, {"score":{"$gt":80}} ]}).hint({"age":-1,"score":-1}).explain(); 删除索引
db.students.dropIndex({"age":-1,"score":-1}); 删除全部索引，但是不会删除主键索引
db.students.dropIndexes();
唯一索引
主要的目的是使得某个字段上的内容不重复。
范例：创建一个唯一索引
db.students.ensureIndex({"name":1},{"unique":true}); /* 1 */[ { "v" : 1, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "mldn.students" }, { "v" : 1, "unique" : true, "key" : { "name" : 1.0 }, "name" : "name_1", "ns" : "mldn.students" }] 这个时候如果插入的姓名已存在，将会报错。
E11000 duplicate key error collection: mldn.students index: name_1 dup key: { : "张三" } 过期索引
用于手机验证码之类的与时间期限的数据。
db.phones.ensureIndex({"time":1},{expireAfterSeconds:10});db.phones.insert({"tel":"110","code":"110","time":new Date()});db.phones.insert({"tel":"111","code":"111","time":new Date()});db.phones.insert({"tel":"112","code":"112","time":new Date()});db.phones.insert({"tel":"113","code":"113","time":new Date()});db.phones.insert({"tel":"114","code":"114","time":new Date()});db.phones.insert({"tel":"115","code":"115","time":new Date()});db.phones.insert({"tel":"116","code":"116","time":new Date()});db.phones.insert({"tel":"117","code":"117","time":new Date()}); 设置过期时间10秒，但是会有延迟。时间到了后，会删除。
全文索引
db.news.insert({"title":"aaa","content":"啦啦啦"});db.news.insert({"title":"bbb","content":"乐乐乐"});db.news.insert({"title":"ccc","content":"咕咕咕"});db.news.insert({"title":"ddd","content":"噜噜噜"});db.news.insert({"title":"eee","content":"驴驴驴"});db.news.insert({"title":"abc","content":"啦乐噜"}); db.news.ensureIndex({"title":"text","content":"text"}); 地理索引
插入数据
db.shop.insert({loc:[10,10]});db.shop.insert({loc:[11,10]});db.shop.insert({loc:[10,11]});db.shop.insert({loc:[12,15]});db.shop.insert({loc:[16,17]});db.shop.insert({loc:[90,90]});db.shop.insert({loc:[120,130]}); 范例: 为shop的集合定义2D索引
db.shop.ensureIndex({"loc":"2d"}); near,geoWithin
范例：查询[11,11]附近的点
db.shop.find({"loc":{"$near":[11,11]}}); 默认返回100条
db.shop.find({"loc":{"$near":[11,11],"$maxDistance":5}});