Having a large number of releases causes performance of a plan to become slow

Issue Summary

Having a large number of releases (>500) causes plan performance, especially on load, to drop dramatically.

Steps to Reproduce

1. Have over 500 releases in a plan

Expected Results

Performance is not affected, plan loads at normal speed

Actual Results

Actual Results
Performance can drop quite dramatically as the number of releases grows past 500.

Cases seen:

~500 releases - 1 minute loading time for plan

~700 releases - 2 minute loading time for plan

~5000 releases - 10 minute loading tie for plan

Workaround

1. Go to the Plan settings > Issue sources > Edit issue sources. Then in the wizard - step 2, unselect the COMPLETED releases. 
2. Go to the Plan settings > Issue sources > Edit issue sources. Then in the wizard - step 1, select Filter and select a filter where the completed releases are excluded.