Nosql Mongodb之旅(28)—MongoDB管理维护Sharding

    1、列出所有的Shard Server

 > db.runCommand({ listshards: 1 }) --列出所有的Shard Server
 {
 "shards" : [
 {
 "_id" : "shard0000",
 "host" : "localhost:20000"
 },
 {
 "_id" : "shard0001",
 "host" : "localhost:20001"
 }
 ],
 "ok" : 1
 }

    2、查看Sharding信息

 > printShardingStatus() --查看Sharding 信息
 --- Sharding Status ---
 sharding version: { "_id" : 1, "version" : 3 }
 shards:
 { "_id" : "shard0000", "host" : "localhost:20000" }
 { "_id" : "shard0001", "host" : "localhost:20001" }
 databases:
 { "_id" : "admin", "partitioned" : false, "primary" : "config" }
 { "_id" : "test", "partitioned" : true, "primary" : "shard0000" }
 test.users chunks:
 shard0000 1
 { "_id" : { $minKey : 1 } } -->> { "_id" : { $maxKey : 1 } } on :
 shard0000 { "t" : 1000, "i" : 0 }
 >

    3、判断是否是Sharding

 > db.runCommand({ isdbgrid:1 })
 { "isdbgrid" : 1, "hostname" : "localhost", "ok" : 1 }
 >

    4、对现有的集合进行分片（实例）

    刚才我们是对表test.users 进行分片了，下面我们将对库中现有的未分片的表test.users_2 进行分片处理。

    表最初状态如下，可以看出他没有被分片过：

 > db.users_2.stats()
 {
 "ns" : "test.users_2",
 "sharded" : false,
 "primary" : "shard0000",
 "ns" : "test.users_2",
 "count" : 500000,
 "size" : 48000016,
 "avgObjSize" : 96.000032,
 "storageSize" : 61875968,
 "numExtents" : 11,
 "nindexes" : 1,
 "lastExtentSize" : 15001856,
 "paddingFactor" : 1,
 "flags" : 1,
 "totalIndexSize" : 20807680,
 "indexSizes" : {
 "_id_" : 20807680
 },
 "ok" : 1
 }

    对其进行分片处理:

 > use admin
 switched to db admin
 > db.runCommand({ shardcollection: "test.users_2", key: { _id:1 }})
 { "collectionsharded" : "test.users_2", "ok" : 1 }

    再次查看分片后的表的状态，可以看到它已经被我们分片了

 > use test
 switched to db test
 > db.users_2.stats()
 {
 "sharded" : true,
 "ns" : "test.users_2",
 "count" : 505462,
 ……
 "shards" : {
 "shard0000" : {
 "ns" : "test.users_2",
 ……
 "ok" : 1
 },
 "shard0001" : {
 "ns" : "test.users_2",
 ……
 "ok" : 1
 }
 },
 "ok" : 1
 }
 >