How to reassign JIRA issues/comments with SQL

below is touching JIRA db directry, apparently not supported by Atlassian

• replace old_username, new_username and project_id appropriately

Update issues - jiraissues

update public.jiraissue set assignee = 'new_username' where assignee = 'old_username'

Update comments - jiraactions

update jiraaction set author = 'new_username' where author = 'old_username_here'
 and actiontype = 'comment' and issueid in (select id from jiraissue where project='project_id');

update public.jiraaction set author = 'new_username' where author = 'old_username'

update public.jiraaction set updateauthor = 'new_username' where updateauthor = 'old_username'

Need to re-index

Done