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learn-build-service-prod merged 5 commits into from
Nov 30, 2025
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Repo sync for protected branch #2790

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KUS: update management command
ktalmor Nov 30, 2025
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changes from PR#2785
ktalmor Nov 30, 2025
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Merge pull request #7232 from ktalmor/KUS-update-management-command
prmerger-automator[bot] Nov 30, 2025
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Merge pull request #7233 from MicrosoftDocs/main
learn-build-service-prod[bot] Nov 30, 2025
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17 changes: 15 additions & 2 deletions data-explorer/kusto/management/alter-query-acceleration-policy-command.md
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Expand Up @@ -3,7 +3,7 @@ title: .alter query acceleration policy command
description: Learn how to use the .alter query acceleration policy command to accelerate queries over external delta tables.
ms.reviewer: sharmaanshul
ms.topic: reference
ms.date: 09/16/2025
ms.date: 11/30/2025
---

# `.alter query acceleration policy` command
Expand All @@ -30,17 +30,21 @@ You must have at least [Database Admin](../access-control/role-based-access-cont
| _JSON-serialized policy_ | `string` | :heavy_check_mark: | String literal holding a [JSON property bag](#json-property-bag). |

### JSON property bag

::: moniker range="microsoft-fabric"

| Property | Type | Required | Description |
| ------------------- | ---------- | ------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
| IsEnabled | `Boolean` | :heavy_check_mark: | Indicates whether the policy is enabled. |
| Hot | `Timespan` | :heavy_check_mark: | The hot period defined in the query acceleration policy. Minimum value = 1 d. |
| HotWindows | `DateTime` | | One or more optional time windows. Delta data files created within these time windows are accelerated. |
| MaxAge | `Timespan` | | The external table returns accelerated data if the last index refresh time is greater than @now - MaxAge. Otherwise, the external table operates in non-accelerated mode. Default is 5 minutes. Minimum is 1 minute. This property can also be overridden at query time by using the [`external_table()` function's](../query/external-table-function.md) `MaxAgeOverride` parameter. |
| HotDateTimeColumn | `String` | | Optional. The name of a datetime column in the Delta table whose values will be used to determine hot-cache eligibility. When set, data files whose rows have values within the configured Hot period (and/or HotWindows) are selected for caching. |

::: moniker-end

::: moniker range="azure-data-explorer"

| Property | Type | Required | Description |
| ------------------- | ---------- | ------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| IsEnabled | `Boolean` | :heavy_check_mark: | Indicates whether the policy is enabled. |
Expand All @@ -49,9 +53,12 @@ You must have at least [Database Admin](../access-control/role-based-access-cont
| MaxAge | `Timespan` | | The external table returns accelerated data if the last index refresh time is greater than @now - MaxAge. Otherwise, the external table operates in non-accelerated mode. Default is 5 minutes. Minimum is 1 minute. This property can also be overridden at query time by using the [`external_table()` function's](../query/external-table-function.md) `MaxAgeOverride` parameter. |
| ManagedIdentity | `string` | | Optional managed identity for which the query acceleration background operations are executed. This identity must have relevant delta table permissions and must be enabled for AutomatedFlows in the cluster / database managed identity policy. For more information, see [Managed identities overview](/azure/data-explorer/managed-identities-overview). |
| HotDateTimeColumn | `String` | | Optional. The name of a datetime column in the Delta table whose values will be used to determine hot-cache eligibility. When set, data files whose rows have values within the configured Hot period (and/or HotWindows) are selected for caching. |

::: moniker-end

> [!NOTE]
> Query acceleration is applied to data within a specific time period, defined as `timespan`, starting from the `modificationTime` as stated for each file in the [delta log](https://github.com/delta-io/delta/blob/master/PROTOCOL.md#add-file-and-remove-file).
>
> Query acceleration is applied to data within a specific time period, based on the `modificationTime` as stated for each file in the [delta log](https://github.com/delta-io/delta/blob/master/PROTOCOL.md#add-file-and-remove-file) by default. You can override the default behavior, by specifying the _HotDateTimeColumn_ property in the policy.

### Example

Expand All @@ -72,17 +79,23 @@ The command returns a table with one record that includes the modified policy ob
| EntityType | `string` | The type of the entity the policy applies to - `ExternalTable` |

## Example

::: moniker range="microsoft-fabric"

```Kusto
.alter external table MyExternalTable policy query_acceleration '{"IsEnabled": true, "Hot": "1.00:00:00", "HotWindows":[{"MinValue":"2025-07-07 07:00:00","MaxValue":"2025-07-09 07:00:00"}], "MaxAge": "00:05:00", "HotDateTimeColumn":"dt1"}'
```

::: moniker-end

::: moniker range="azure-data-explorer"

```Kusto
.alter external table MyExternalTable policy query_acceleration '{"IsEnabled": true, "Hot": "1.00:00:00", "HotWindows":[{"MinValue":"2025-07-07 07:00:00","MaxValue":"2025-07-09 07:00:00"}], "MaxAge": "00:05:00", "ManagedIdentity": "12345678-1234-1234-1234-1234567890ab", "HotDateTimeColumn":"dt1"}'
```

::: moniker-end

## Related content

- [Query acceleration policy](query-acceleration-policy.md)
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