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.disable | .enable materialized-view
Applies to: ✅ Microsoft Fabric ✅ Azure Data Explorer
Disables or enables the materialization process for a materialized view.
Note
Because there are some important performance implications associated with disabling/enabling a materialized view, make sure you are familiarized with them before you proceed with the use of this command. For more information, see the Performance implications of enabling/disabling materialized views section.
Permissions
You must have at least Materialized View Admin to run these commands.
Syntax
.enable | disable materialized-view MaterializedViewName
Learn more about syntax conventions.
Parameters
| Name | Type | Required | Description |
|---|---|---|---|
| MaterializedViewName | string |
✔️ | Name of the materialized view. |
Returns
If the materialized view is already in the state in which the command is trying to set it to, the command fails with an error indicating that is the case.
Otherwise, it returns the details about the materialized view whose IsEnabled property has been changed.
Output schema:
| Name | Type | Description |
|---|---|---|
| Name | string |
Name of the materialized view. |
| SourceTable | string |
Name of source table on which the view is defined. |
| Query | string |
Query definition of the materialized view. |
| MaterializedTo | datetime |
Maximum materialized ingestion_time() timestamp in source table. For more information, see how materialized views work. |
| LastRun | datetime |
Last time materialization was run. |
| LastRunResult | string |
Result of last run. Returns Completed for successful runs, otherwise Failed. |
| IsHealthy | bool |
true when view is considered healthy, false otherwise. View is considered healthy if it was successfully materialized up to the last hour (MaterializedTo is greater than ago(1h)). |
| IsEnabled | bool |
true when view is enabled (see Disable or enable materialized view). |
| Folder | string |
Folder under which the materialized view is created. |
| DocString | string |
Description assigned to the materialized view. |
| AutoUpdateSchema | bool |
Whether the view is enabled for auto updates. |
| EffectiveDateTime | datetime |
Effective date time of the view, determined during creation time (see .create materialized-view). |
| Lookback | timespan |
Time span limiting the period of time in which duplicates are expected. |
Examples
Enable a materialized view
The following command enables materialized view ViewName:
.enable materialized-view ViewName
Output
| Name | SourceTable | Query | MaterializedTo | LastRun | LastRunResult | IsHealthy | IsEnabled | Folder | DocString | AutoUpdateSchema | EffectiveDateTime | Lookback |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ViewName | TableName | TableName | summarize arg_max(Column3, *) by Column1 | 2023-02-26T16:40:03.3345704Z | 2023-02-26T16:44:15.9033667Z | Completed | true | true | false | 2023-02-23T14:01:42.5172342Z |
Disable a materialized view
The following command disables materialized view ViewName:
.disable materialized-view ViewName
Output
| Name | SourceTable | Query | MaterializedTo | LastRun | LastRunResult | IsHealthy | IsEnabled | Folder | DocString | AutoUpdateSchema | EffectiveDateTime | Lookback |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| ViewName | TableName | TableName | summarize arg_max(Column3, *) by Column1 | 2023-02-26T16:40:03.3345704Z | 2023-02-26T16:44:15.9033667Z | Completed | true | false | false | 2023-02-23T14:01:42.5172342Z |
Remarks
Disabling materialized views
A materialized view can be disabled in any of the following ways:
- Automatic disable by the system: Materialized view is automatically disabled if materialization fails with a permanent error. This process can occur in the following instances:
- Schema changes that are inconsistent with the view definition.
- Changes to source table that result in the materialized view query being semantically invalid.
- Explicitly disable the materialized view: If the materialized view is negatively impacting the database's health (for example, consuming too much CPU), disable the view using the
.disable materialized-viewcommand.
Materialized views and Row Level Security
If a materialized view is disabled, and while the view is disabled someone defines a row level security policy on the source table of the view, but the materialized view doesn't have a row level security policy defined, then enabling the view fails for security reasons. To mitigate this error, you can:
- Define the row level security policy over the materialized view.
- Choose to ignore the error by adding
allowMaterializedViewsWithoutRowLevelSecurityproperty to the enable policy command. For example:
.enable materialized-view MV with (allowMaterializedViewsWithoutRowLevelSecurity=true)
Performance implications of enabling/disabling materialized views
- When a materialized view is disabled, materializing will be paused and won't consume resources from the database. Querying the materialized view is possible even when disabled, but performance can be poor. Performance on a disabled materialized view depends on the number of records that were ingested to the source table since it was disabled.
- You can enable a materialized view that has previously been disabled. When re-enabled, the materialized view will continue materializing from the point it left off, and no records will be skipped. If the view was disabled for a long time, it may take a long time to catch up.
- Disabling a view is only recommended if you suspect that the view is impacting your database's health.