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configureCollectionBalancing

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Definition

Syntax

The command has the following syntax:

copy 
db.adminCommand(
   {
     configureCollectionBalancing: "<collection>",
     chunkSize: <num>,
     defragmentCollection: <bool>
   }
)

Command Fields

:dbcommand:`configureCollectionBalancing` has the following fields:

Field Type 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.
defragmentCollection boolean Optional: Causes the balancer to defragment the collection.

For more information, see Data Partitioning with Chunks.

Behavior

No Collection chunkSize 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 :dbcommand:`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 Chunk Size in a Sharded Cluster.

Examples

Configure Chunk Size

To change the chunk size for a sharded collection, use the chunkSize option:

copy 
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 :method:`db.collection.stats()` method.

For more information, see Chunk Size.

Defragment Collections

To tell the balancer to defragment a sharded collection, use the defragmentCollection option:

copy 
db.adminCommand( {
   configureCollectionBalancing: "test.students",
   defragmentCollection: true
} )

Use this command to have the balancer defragment a sharded collection.

Reconfigure and Defragment Collections

To defragment a sharded collection while updating the chunk size, use the defragmentCollection option and the chunkSize option together:

copy 
db.adminCommand( {
   configureCollectionBalancing: "test.students",
   chunkSize: 512,
   defragmentCollection: true
} )

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