ALTER TAG

Modifies an existing tag definition in the catalog.

Syntax

ALTER TAG <name> SET [DESCRIPTION '<desc>'] [CATEGORY <cat>]
  [ALLOWED VALUES ('<v1>', '<v2>', ...)] [PROPAGATE ON|OFF]

Description

## Overview Modifies one or more properties of an existing tag definition. Tags are governance primitives stored in the control plane catalog. They classify and annotate tables, views, and columns for policy enforcement, data discovery, and compliance reporting. Only the properties specified in the statement are changed; unmentioned properties retain their current values. ## Behavior - The SET keyword is optional but recommended for readability. - If the named tag does not exist, the command returns an error. Use DESCRIBE TAG to verify existence before altering. - Changing ALLOWED VALUES replaces the entire allowed-values list. Existing tag assignments whose values are no longer in the new list are not automatically removed; they become non-conformant until re-assigned. - Setting PROPAGATE ON causes future SET TAG assignments on a table to cascade to all columns of that table. Existing assignments are not retroactively propagated. - The command routes through the control plane catalog API. A valid control plane connection is required. ## Compatibility ALTER TAG is a DeltaForge extension. There is no ANSI SQL equivalent. The tag system provides governance metadata similar to classification labels in enterprise data catalog products.

Examples

-- Update the description of an existing tag
ALTER TAG pii_type SET DESCRIPTION 'Personally identifiable information classifier';

-- Change the category and add new allowed values
ALTER TAG sensitivity SET CATEGORY compliance ALLOWED VALUES ('public', 'internal', 'confidential', 'restricted');

-- Enable propagation so the tag cascades to child columns
ALTER TAG data_domain SET PROPAGATE ON;

-- Clear the allowed-values restriction to permit any value
ALTER TAG custom_label SET ALLOWED VALUES;

-- Combine multiple changes in a single statement
ALTER TAG retention_policy SET DESCRIPTION 'Data retention period' CATEGORY compliance ALLOWED VALUES ('30d', '90d', '1y', '7y') PROPAGATE OFF;

Pitfalls

• Changing ALLOWED VALUES does not validate or remove existing tag assignments that use values outside the new list. Audit assignments after narrowing allowed values.
• PROPAGATE ON only affects future SET TAG operations. To propagate an existing tag to child columns, unset and re-set it after enabling propagation.
• Omitting ON or OFF after PROPAGATE defaults to ON. If the intent is to leave propagation unchanged, omit the PROPAGATE clause entirely.

See Also

• CREATE_TAG
• DROP_TAG
• DESCRIBE_TAG
• SET_TAG
• SHOW_TAGS