A large change history or worklog on an issue can cause an OOME when displaying the History tab

Summary

Having a huge amount of changeitems and changegroups (20,000) will cause the instance to OOME when viewing the History tab.

Steps to Reproduce

1. Create a change log of over 20,000 entries for one issue.
2. View the issue history tab for that issue.

Expected Results

Full change log should be displayed.

Actual Results

The instance will be out of memory and restart.

Notes

• SQL to find large number of changes per issue:

  select concat(p.pkey,'-',ji.issuenum) as issue, count (ji.id) from changeitem ci join changegroup cg on cg.id = ci.groupid join jiraissue ji on cg.issueid = ji.id join project p on p.id = ji.project group by ji.issuenum,p.pkey order by count (ji.id) DESC;
     issue    | count
  ------------+-------
   PRG-5      |    50
   AG-4       |    17
   AG-12      |    14
   AG-16      |    13
  

• SQL to find large number of actions (comments ... ) per issue:

  select concat(p.pkey,'-',i.issuenum) as issue, count(i.id) from jiraaction a, jiraissue i, project p where i.project = p.id and i.id = a.issueid group by p.pkey,i.issuenum order by count (i.id) DESC;
  

• SQL to identify issues with large worklog history:

  select issueid, count(id) from worklog group by issueid having count(id) > 100 order by (count(id)) desc;
  

Workaround

Using the queries above, we can identify the issues with large changeitems and changegroups information.

Next, clone the issue on the list as the case history is not cloned to the new issue.