Problem

Whenever an issue is being indexed, Jira retrieves all registered custom field indexers and calls their addIndex() method regardless of whether the custom field is applicable (visible and in the context) for the issue or not. This generates additional overhead and affects indexing time.

Note: The custom field is considered as visible when it is not hidden in Field Configuration menu. Screens are not used to calculate fields visibility - the field may be not assigned to any screen, but still be considered as visible.

Solution

To mitigate it we switched all custom fields to be indexed only when they are applicable for the particular issue.

This feature is only available in Jira Data Center 8.10 and later.
See also: Optimizing custom fields