JIRA performance degrades when a large number of security levels are used

Summary

When a JIRA Instance has many Security Levels the performance of JIRA can degrade significantly.

Steps to Reproduce

1. Configure an environment with many Projects and Issue Security Configuration.
2. Observe a degradation of performance on the instance.
3. Thread dumps from an affected JIRA instance may indicate many threads showing a stack traces involving IssueSecurity.

Expected Results

JIRA should remain performant and cope with the scale in issues or issue security.

Actual Results

JIRA becomes unresponsive with large numbers of issue security levels configured.

Notes

Configuring Issue level Security currently indicates thar setting more than 10 issue security levels can impact performance in JIRA.

Workaround

1. Run the following SQL to check the number of security level:

   select scheme, count(security) from schemeissuesecurities group by scheme;
   scheme | count
   --------+-------
     10000 |  1279
     10030 |    3
     ...
   (7 rows)

2. Reduce the issue security levels.
3. Reduce the number of groups using in each level.