configureCollectionBalancing
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Definition
Syntax
The command has the following syntax:
db.adminCommand( { configureCollectionBalancing: "<db>.<collection>", chunkSize: <num>, defragmentCollection: <bool> enableAutoMerger: <bool> } )
Command Fields
configureCollectionBalancing has the following fields:
Field | Type | Necessity | Description |
|---|---|---|---|
configureCollectionBalancing | string | Required | The name of the database and sharded collection to configure. |
chunkSize | integer | Optional | Sets the chunk size in MiB for the collection. The
recommended size is 256, 512, or larger. For details on default
behavior, see Default Behavior When chunkSize Is Not Specified. |
defragmentCollection | boolean | Optional | Causes the balancer to defragment the collection.
Defaults to false. |
enableAutoMerger | boolean | Optional | Whether or not the AutoMerger takes this collection into account.
Defaults to true. |
For more information, see Data Partitioning with Chunks.
To configure the chunk defragmentation throttling time parameter, see
chunkDefragmentationThrottlingMS.
To learn about defragmenting sharded collections, see Defragment Sharded Collections.
Behavior
Default Behavior When chunkSize Is Not Specified
If you do not specify chunkSize for a collection and no custom size
has been set previously, the global default chunkSize is
used for balancing.
Specifying chunkSize: 0
If you use configureCollectionBalancing with
chunkSize: 0, the per-collection chunkSize is reset and the
global default chunkSize is used for balancing.
For more information on configuring default chunkSize,
see Modify Range Size in a Sharded Cluster.
Default Behavior When enableAutoMerger Is Not Specified
If you do not specify enableAutoMerger for a collection and no
custom automerging behavior has been previously set, it
defaults to true and will be taken into account by the
AutoMerger.
Examples
Configure Chunk Size
To change the chunk size for a sharded collection, use
the chunkSize option:
db.adminCommand( { configureCollectionBalancing: "test.students", chunkSize: 256 } )
Use this command to change the chunk size for the given collection.
Warning
By default, MongoDB cannot move a chunk if the number of documents in the chunk is greater than 1.3 times the result of dividing the configured chunk size by the average document size.
To find the average document size, see the avgObjSize field in the
output of the db.collection.stats() method.
For more information, see Range Size.
Defragment Collections
Warning
We do not recommend using defragmentCollection to defragment sharded
collections for MongoDB 6.0.0 to 6.0.3 and MongoDB 6.1.0 to 6.1.1, as the
defragmentation process on these releases can make databases and collections
unavailable for extended periods of time.
To tell the balancer to defragment a sharded collection, use the
defragmentCollection option:
db.adminCommand( { configureCollectionBalancing: "test.students", defragmentCollection: true } )
Use this command to have the balancer defragment a sharded collection.
To monitor the chunk defragmentation process, use the
balancerCollectionStatus command.
To learn more about defragmenting sharded collections, see Defragment Sharded Collections.
Reconfigure and Defragment Collections
To defragment a sharded collection while updating the chunk size, use
the defragmentCollection option and the chunkSize option
together:
db.adminCommand( { configureCollectionBalancing: "test.students", chunkSize: 512, defragmentCollection: true } )
Disable the AutoMerger on a Collection
To explicitly disable the AutoMerger on a collection,
set the enableAutoMerger option to false:
db.adminCommand( { configureCollectionBalancing: "test.students", enableAutoMerger: false } )