Attempt to optimize ghost generating code.

Summary: Ref T8394, Attempt to optimize ghost generating code.

Test Plan: Open Upcoming, cancelled only, list view query. Should not hang.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Maniphest Tasks: T8394

Differential Revision: https://secure.phabricator.com/D13141