Data sharding policy

The sharding policy defines if and how extents (data shards) in the Azure Data Explorer cluster are created. You can only query data in an extent once it's created.


The data sharding policy contains the following properties:

  • MaxRowCount:

    • Maximum row count for an extent created by an ingestion or rebuild operation.
    • Defaults to 750,000.
    • Not in effect for merge operations.
      • If you must limit the number of rows in extents created by merge operations, adjust the RowCountUpperBoundForMerge property in the entity's extents merge policy.
  • MaxExtentSizeInMb:

    • Maximum allowed compressed data size (in megabytes) for an extent created by a merge operation.
    • In effect only for merge operations.
    • Defaults to 1,024 (1GB).
  • MaxOriginalSizeInMb:

    • Maximum allowed original data size (in megabytes) for an extent created by a rebuild operation.
    • In effect only for rebuild operations.
    • Defaults to 2,048 (2GB).


Consult with the Azure Data Explorer team before altering a data sharding policy.

When a database is created, it contains the default data sharding policy. This policy is inherited by all tables created in the database (unless the policy is explicitly overridden at the table level).

Use the sharding policy control commands to manage data sharding policies for databases and tables.