extent_id()

Learn how to use the extent_id() function to return an identifier of the current record’s data shard

Provides a unique identifier for the data shard (“extent”) containing the current record at the time the query was run.

Applying this function to calculated data that isn’t attached to a data shard returns an empty guid (all zeros).

Syntax

extent_id()

Returns

Returns a value of type guid that identifies the current record’s data shard at the time the query was run, or an empty guid (all zeros).

Examples

The following example shows how to get a list of all the data shards that currently have records from an hour ago with a specific value for the column ActivityId. It demonstrates that some query operators (here, the where operator, and also extend and project) preserve the information about the data shard hosting the record.

T
| where Timestamp > ago(1h)
| where ActivityId == 'dd0595d4-183e-494e-b88e-54c52fe90e5a'
| extend eid=extent_id()
| summarize by eid