Large number of options in Multi Select Custom Field hangs browser in Create Issue popup when changing projects

Summary

This issue has the same context and root cause as JRASERVER-44588 : Multi Select Custom Field loads options in a suboptimal way, but describes a different performance implication. JRASERVER-44588 discusses REST and DB performance on the JIRA server backend. This describes browser frontend performance.

In an environment which has a Multi Select Custom Field with very many options (at least 1000, but performance implications are more visible at larger numbers, such as 10,000), if said custom field is added to the Create Issue screen for a project, it is possible for the Create Issue popup dialog to become unresponsive when switching projects from said project associated with the custom field, to a different project.

Environment

Performance seems to be substantially worse in Google Chrome than in Firefox. (~17 seconds in Chrome vs ~2 seconds in Firefox in a fresh environment with a Multi Select Custom Field with 10,000 options)

Steps to Reproduce

1. Create a new Select List (multiple choice) custom field
2. Add at least 1000 options, but recommended 10000 options to the field
3. Associate the custom field to at least one project's Create Issue screen
4. Navigate to a Dashboard
5. Click the Create button at the top of JIRA to bring up the Create Issue popup box
6. If not currently on a project with the custom field on it's Create Issue screen, change to one of those projects first.
7. Change projects away from the project associated with the custom field

Expected Results

There will be no unresponsiveness, and the projects can be switched within a short period of time.

Actual Results

The browser will be unresponsive while scripting is occurring, with the duration depending on the number of options being loaded and the performance of the browser's physical machine.

See JRASERVER-66086.mp4 for a demonstration of unresponsiveness in Google Chrome, along with Chrome's Performance Profiler results.

Notes

The performance issue does not occur if trying to create an issue via $JIRA_URL/secure/CreateIssue!default.jspa; only when using the popup window (i.e. when creating an issue from a Dashboard).

Workaround

Use Firefox, as the performance issue appears to be either much less significant, or outright nonexistent.