mongodb sharding-range分片

范围分片

注：hash分片通常是为了规避单调递增写热点

range分片通常是为了提升范围区间查询，不广播所有分片

也可hash+range结合方式来分片，兼顾写分散，读收敛

如：订单类 {customer_id:“hashed”,order_date:1}

mongo --port 27000 --host 127.0.0.1
use admin
db.auth("admin","Admin@01");
#删除测试collection: testdb.person 
use testdb
db.person.drop()
#启动testdb.person，按省2份分片
sh.enableSharding("testdb")
sh.shardCollection("testdb.person",{province:1})
db.person.getIndexes()
load("/home/mongo/testdb_func.js")
#停平衡器
db.printShardingStatus()
db.person.createIndex({province:1,age:1})
db.adminCommand( {
   refineCollectionShardKey: "testdb.person",
   key: { province: 1, age: 1 }
} )
#启动平衡器

重定义分片键

重定义必须满足如下条件

4.4版本以上或兼容4.4
新分片键必须有相同的前缀，即按已存在的分片键扩展
新字段只能添加做后缀
需要先建立新索引包含新的分片键
重定义分片键需关闭均衡器

具体步骤

1.检查当前库版本

db.version()

2.当前FCV版本需4.4或之后版本

db.adminCommand( { getParameter: 1, featureCompatibilityVersion: 1 } )

3.关闭均衡器 (on mongos)

sh.getBalancerState()      # check state             (assuming “true”)
sh.isBalancerRunning()     # check if running      (assuming “true”)
sh.stopBalancer()          # stop the balancer
sh.getBalancerState()      # check state             (assuming “false”)      
sh.isBalancerRunning()     # check if running      (assuming “false”)

4.如果需要设置FCV

注：除非升级，否则不要轻易修改FCV兼容

db.adminCommand( { setFeatureCompatibilityVersion: "4.4" } )

5创建索引支持新分片键

db.<collection>.createIndex(keys, options)
db.<collection>.getIndexes();

6.运行refineCollectionShardKey 扩展分片键字段

db.adminCommand( {
   refineCollectionShardKey: "<database>.<collection>",
   key: { <existing key specification>, <suffix1>: <1|"hashed">, ... }
} )

7.检查分片状态确保修改生效

sh.status()

8.重启均衡器 (on mongos)

use config
sh.startBalancer()         # start the balancer
sh.getBalancerState()      # check state             (assuming “true”)
sh.isBalancerRunning()     # check if running      (assuming “true”)