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With the growth of business, MongoDB can change a collection that was not sharded into a sharding collection, but it is important to note that once shard key is specified, it cannot be changed directly. Here are the specific steps from adding shard server to shard key

1) add shard server

Add context:

1.1) insufficient data storage directory 1.2) unable to meet the current production write operations 1.3) too many chunk

3) change the collection into a fragmented collection

The key to add a part needs to create an index, otherwise an error please create an index that starts with the shard key before sharding will be reported.

According to the above error, you need to create an index on the shard key. The index should be built under the corresponding library. If you build it under the admin library of mongos, you will get an error: "errmsg": "{configs1/10.9.33.70:26017,10.9.161.65:26017:\" result without error message returned: {}\ "}".

4) migrate data manually

If balance is enabled, the data will be broken up automatically. If it is not enabled, you need to manually move the data for the first time:

5) Delete the sharding of the sharding collection

Sh.setBalancerState (true); ensure that balance is enabled before the data on the deleted shard is automatically migrated to other shards. Draining ": true,-- data is being migrated.

This command can be repeated to see the status of the migration, and the remaining field indicates the number of blocks remaining

6) delete the main shard that is not sliced

If the database is not shredded, the database will select a shard as the primary shard. The "primary": "mg-test-shard01" display in Db.collection.stats () is the main shard. To delete this master shard, you need to change the collection master shard to another shard before deleting the master shard.

Click (here) to collapse or open

Db.runCommand ({movePrimary: "db_name", to: "new_shard"}) db.runCommand ({removeshard: "mg-test-shard01/10.9.161.65:27019,10.9.33.70:27019"})

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