Cloud to Server Import will show existing mentions with AccountID rather than name

Issue Summary

Existing mentions are shown with AccountID after backup is imported into Jira Server from Cloud.

Environment

Jira 8.4.1

Steps to Reproduce

1. Mention a user in Jira Cloud, you should see their name on the mention once you save the comment.
2. Generate a backup for Server and restore this to a Server instance
3. Check the same issue you mentioned previously in Cloud

Expected Results

The Users name still present on the issue

Actual Results

The AccountID is shown instead:

Notes

• Related to changes made in Cloud due to GDPR:
  • Say goodbye to usernames in Atlassian Cloud
  • Changes to usernames in Jira Cloud
• We see from the database that the AID is mapped to the username in the external_id column in Jira Server.

Workaround

This should give you a list of update queries to run, we recommend testing this in a lower enviornment and as always backing up the DB before running anything

PostgreSQL:

SELECT ('UPDATE jiraaction SET actionbody = replace(actionbody, ''accountid:' || cu.external_id || ''', ''' || cu.lower_user_name || ''') WHERE actionbody LIKE ''%[~accountid:' || cu.external_id || ']%'';') as "Queries to fix" FROM cwd_user cu WHERE cu.external_id IS NOT NULL; 

MySQL:

SELECT (CONCAT('UPDATE jiraaction SET actionbody = replace(actionbody, ''accountid:' , ifnull(cu.external_id, '') , ''', ''' , ifnull(cu.lower_user_name, '') , ''') WHERE actionbody LIKE ''%[~accountid:' , ifnull(cu.external_id, '') , ']%'';')) as "Queries to fix" FROM cwd_user cu WHERE cu.external_id IS NOT NULL; 

Workaround 2

We noticed that if you desire to change the email accounts of users, the queries above would fail to migrate the mentions correctly.
For the migration to be successful, we need to update the "actionbody" column with the "user_name" value and then change the email account of the user:

1. Use the query below to generate the updates:

   --QUERIES FOR POSTGRES
   SELECT ('UPDATE jiraaction SET actionbody = replace(actionbody, ''accountid:' || cu.external_id || ''', ''' || cu.user_name || ''') WHERE actionbody LIKE ''%[~accountid:' || cu.external_id || ']%'';') as "Queries to fix" FROM cwd_user cu WHERE cu.external_id IS NOT NULL;

2. Run the generated queries.
3. Update the user's email accounts.