查询索引

1. 索引存放在system.indexes集合中
2. > show tables
3. address
4. data
5. person
6. system.indexes
7. 默认会为所有的ID建上索引 而且无法删除
8. > db.system.indexes.find()
9. { "v" : 1, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "mydb.person" }
10. { "v" : 1, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "mydb.address" }
11. { "v" : 1, "key" : { "_id" : 1 }, "name" : "_id_", "ns" : "mydb.data" }
12. 单独查询一个集合的索引
13. > db.person.getIndexes();
14. [
15.    {
16.       "v" : 1,
17.       "key" : {
18.          "_id" : 1
19.       },
20.       "name" : "_id_",
21.       "ns" : "mydb.person"
22.    }
23. ]
24. >

创建索引

1. > db.person.find();
2. { "_id" : ObjectId("593011c8a92497992cdfac10"), "name" : "xhj", "age" : 30, "address" : DBRef("address", ObjectId("59314b07e693aae7a5eb72ab")) }
3. { "_id" : ObjectId("59301270a92497992cdfac11"), "name" : "zzj", "age" : 2 }
4. { "_id" : ObjectId("593015fda92497992cdfac12"), "name" : "my second child", "age" : "i do not know" }
5. { "_id" : ObjectId("592ffd872108e8e79ea902b0"), "name" : "zjf", "age" : 30, "address" : { "province" : "河南省", "city" : "南阳市", "building" : "桐柏县" } }
6. 1升序 -1降序
7. > db.person.ensureIndex({age:1});
8. {
9.    "createdCollectionAutomatically" : false,
10.    "numIndexesBefore" : 1,
11.    "numIndexesAfter" : 2,
12.    "ok" : 1
13. }
14. 可以在集合上创建索引
15. > db.person.ensureIndex({address:1});
16. {
17.    "createdCollectionAutomatically" : false,
18.    "numIndexesBefore" : 2,
19.    "numIndexesAfter" : 3,
20.    "ok" : 1
21. }
22. 复合索引
23. > db.person.ensureIndex({name:1,address:1});
24. {
25.    "createdCollectionAutomatically" : false,
26.    "numIndexesBefore" : 3,
27.    "numIndexesAfter" : 4,
28.    "ok" : 1
29. }
30. 唯一索引：
31. > db.person.ensureIndex({name:1},{unique:true});
32. {
33.    "createdCollectionAutomatically" : false,
34.    "numIndexesBefore" : 4,
35.    "numIndexesAfter" : 5,
36.    "ok" : 1
37. }

删除索引：

1. 删除一个索引
2. > db.person.dropIndex({name:1});
3. { "nIndexesWas" : 5, "ok" : 1 }
4. 删除所有索引
5. > db.person.dropIndexes();
6. {
7.    "nIndexesWas" : 4,
8.    "msg" : "non-_id indexes dropped for collection",
9.    "ok" : 1
10. }

Mongodb索引