.alter column policy encoding command
Applies to: ✅ Azure Data Explorer
Alters the encoding policy. For an overview of the encoding policy, see Encoding policy.
Note
Encoding policy changes do not affect data that has already been ingested. Only new ingestion operations will be performed according to the new policy.
Permissions
You must have at least Table Admin permissions to run this command.
Syntax
.alter column EntityIdentifier policy encoding [type = EncodingPolicyType]
Note
If you omit the type, the existing encoding policy profile is cleared reset to the default value.
Learn more about syntax conventions.
Parameters
| Name | Type | Required | Description |
|---|---|---|---|
| EntityIdentifier | string |
✔️ | The identifier for the column. |
| EncodingPolicyType | string |
The type of the encoding policy to apply to the specified column. See encoding policy types for the possible values. |
Encoding policy types
The following table contains the possible values for the EncodingPolicyType parameter.
| Encoding Policy Profile | Description |
|---|---|
Identifier |
Suitable for columns that have data that represents ID-like information (for example, guids). This policy applies the required index for this column to gain both query performance and reduce size in the storage. |
BigObject |
Suitable for columns of dynamic or string type, which holds large objects. For example, the output of hll aggregate function. This policy disables the index of this column and overrides MaxValueSize property in the encoding Policy to 2 MB. |
BigObject32 |
Similar to BigObject in terms of target scenarios. Overrides MaxValueSize property in the encoding Policy to 32 MB. |
Vector16 |
This profile is designed for storing vectors of floating-point numbers in 16 bits precision utilizing the Bfloat16 instead of the default 64 bits. It is highly recommended for storing ML vector embeddings as it reduces storage requirements by a factor of 4 and accelerates vector processing functions such as series_dot_product() and series_cosine_similarity(), by orders of magnitude. |
Null |
Sets the current default encoding policy to the column and clears the previous encoding policy profile. |
Example
.alter column Logs.ActivityId policy encoding type='identifier'