Summary
Keychain - Delegation for Jira custom fields will respond to JQL searches but these fields should not be used directly by JQL.
The values in these fields are calculated dynamically based on delegation definitions and current date. Jira field values for an issue are normally indexed only when the issue is updated. On the other hand, field values in Keychain fields can change when delegation configurations change or simply when the current date progresses. In either case the issue and its index values are not updated.
These fields might return inaccurate results if queried by JQL directly. So we recommend NOT TO USE Keychain custom fields in JQL searches.
Searching
We recommend using the JQL functions described in JQL Functions for searches.
Disabling Search
Jira admins can set the Search Template for a custom field to None. This effectively prevents the field from being indexed and searched by JQL.
You will need to set an indexer and enable search on Keychain fields in cases where you want to use these fields in permission schemes, as described in the case Using Keychain Custom Fields in Permission Schemes.
To set an indexer or remove it, use the Edit option in the custom field's context menu in Custom Fields admin screen.
Change the Search Template in the Edit page to User Picker & Group Searcher to make it searchable and so usable in permission schemes.
If you don't plan to use that field in permission schemes, you can make it unsearchable by changing the Search Template to None.