MongoDB索引管理——創建索引，查看索引，刪除索引，重建索引
阿新 • • 發佈：2018-02-12
大小 exsi ngs 索引 mongodb reat 新建 mon 集合 先給users集合插入兩條記錄，然後用users集合來進行索引管理的演示：
> user1={"name":"liming","age":20,"gender":"F"} { "name" : "liming", "age" : 20, "gender" : "F" } > db.users.insert(user1) WriteResult({ "nInserted" : 1 }) > user2={"name":"zhangsan","age":25,"gender":"F"} { "name" : "zhangsan", "age" : 25, "gender" : "F" } > db.users.insert(user1) WriteResult({ "nInserted" : 1 }) > db.users.count() 2
創建索引：
mongodb使用createIndex()和ensureIndex()方法來創建索引，前者用於3.0及以上版本，後者用於3.0以下版本。
例1：給name字段創建正序索引
> db.users.createIndex({"name":1})
{
"createdCollectionAutomatically" : false,
"numIndexesBefore" : 1,
"numIndexesAfter" : 2,
"ok" : 1
}例2：給name字段創建倒序索引
> db.users.createIndex({"name":-1}) { "createdCollectionAutomatically" : false, "numIndexesBefore" : 2, "numIndexesAfter" : 3, "ok" : 1 }
例3：給name，age字段創建組合索引
> db.users.createIndex({"name":1,"age":1})
{
"createdCollectionAutomatically" : false,
"numIndexesBefore" : 3,
"numIndexesAfter" : 4,
"ok" : 1
}例4：在後臺給age字段創建索引
> db.users.createIndex({age:1},{background:1}) { "createdCollectionAutomatically" : false, "numIndexesBefore" : 4, "numIndexesAfter" : 5, "ok" : 1 }
在後臺創建索引的原因：
在前臺創建索引期間會鎖定數據庫，會導致其它操作無法進行數據讀寫，在後臺創建索引是，會定期釋放寫鎖，從而保證其它操作的運行，但是後臺操作會在耗時更長，尤其是在頻繁進行寫入的服務器上。
查看索引：
MongoDB提供的查看索引信息的方法：
getIndexes()方法可以用來查看集合的所有索引，
getIndexKeys()方法查看索引鍵。
totalIndexSize()查看集合索引的總大小，
getIndexSpecs()方法查看集合各索引的詳細信息
例1： getIndexes()的用法
> db.users.getIndexes()
[
{
"v" : 1,
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "test1.users"
},
{
"v" : 1,
"key" : {
"name" : 1
},
"name" : "name_1",
"ns" : "test1.users"
},
{
"v" : 1,
"key" : {
"name" : -1
},
"name" : "name_-1",
"ns" : "test1.users"
},
{
"v" : 1,
"key" : {
"name" : 1,
"age" : 1
},
"name" : "name_1_age_1",
"ns" : "test1.users"
},
{
"v" : 1,
"key" : {
"age" : 1
},
"name" : "age_1",
"ns" : "test1.users",
"background" : 1
}
]例2：getIndexKeys()的用法
> db.users.getIndexKeys()
[
{
"_id" : 1
},
{
"name" : 1
},
{
"name" : -1
},
{
"name" : 1,
"age" : 1
},
{
"age" : 1
}
]例3：totalIndexSize()的用法
> db.users.totalIndexSize()
81920例4：getIndexSpecs()的用法
> db.users.getIndexSpecs()
[
{
"v" : 1,
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "test1.users"
},
{
"v" : 1,
"key" : {
"name" : 1
},
"name" : "name_1",
"ns" : "test1.users"
},
{
"v" : 1,
"key" : {
"name" : -1
},
"name" : "name_-1",
"ns" : "test1.users"
},
{
"v" : 1,
"key" : {
"name" : 1,
"age" : 1
},
"name" : "name_1_age_1",
"ns" : "test1.users"
},
{
"v" : 1,
"key" : {
"age" : 1
},
"name" : "age_1",
"ns" : "test1.users",
"background" : 1
}
]刪除索引：
不再需要的索引，我們可以將其刪除，mongodb提供兩種刪除索引的方法：
dropIndex()方法用於刪除指定的索引
dropIndexes()方法用於刪除全部的索引
例1:dropIndex()的用法
> db.users.dropIndex("name_1")
{ "nIndexesWas" : 5, "ok" : 1 }
> db.users.dropIndex("name_1_age_1")
{ "nIndexesWas" : 4, "ok" : 1 }
> db.users.getIndexSpecs()
[
{
"v" : 1,
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "test1.users"
},
{
"v" : 1,
"key" : {
"name" : -1
},
"name" : "name_-1",
"ns" : "test1.users"
},
{
"v" : 1,
"key" : {
"age" : 1
},
"name" : "age_1",
"ns" : "test1.users",
"background" : 1
}
]我們可以看到,name字段的索引和name與age字段的組合索引皆被刪除
例2:dropIndexes()的用法
> db.users.dropIndexes()
{
"nIndexesWas" : 3,
"msg" : "non-_id indexes dropped for collection",
"ok" : 1
}
> db.users.getIndexSpecs()
[
{
"v" : 1,
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "test1.users"
}
]在使用了dropIndexes()方法後,我們之前建的所有索引都被刪除掉了
索引重建:
我們之前把users的索引全部刪除了,現在在name字段上建立一個正序索引,然後在name字段上重建倒序索引,可以看到重建索引是把之前name字段的索引刪掉再新建一個索引的,重建之前name字段還是只有一個索引.
> db.users.createIndex({name:1})
{
"createdCollectionAutomatically" : false,
"numIndexesBefore" : 1,
"numIndexesAfter" : 2,
"ok" : 1
}
> db.users.getIndexSpecs()
[
{
"v" : 1,
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "test1.users"
},
{
"v" : 1,
"key" : {
"name" : 1
},
"name" : "name_1",
"ns" : "test1.users"
}
]
> db.users.reIndex({name:-1})
{
"nIndexesWas" : 2,
"nIndexes" : 2,
"indexes" : [
{
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "test1.users"
},
{
"key" : {
"name" : 1
},
"name" : "name_1",
"ns" : "test1.users"
}
],
"ok" : 1
}
> db.users.getIndexSpecs()
[
{
"v" : 1,
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "test1.users"
},
{
"v" : 1,
"key" : {
"name" : 1
},
"name" : "name_1",
"ns" : "test1.users"
}
]MongoDB索引管理——創建索引，查看索引，刪除索引，重建索引