The profile_search table stores recently used searches by the user. When the user starts opening searches in quick succession, this can cause postgres serialization errors to happen. These serialization errors really aren't all that critical for this table and could be safely ignored. In Bugzilla/Search/Recent.pm we should wind the serialization level back to READ COMMITTED where it deletes from the profile_search table.
Test this on build 4.4.10042-7 Before upgrading, QE could get the serialization error when open huge amount tabs of search at once: Red Hat Bugzilla's database reported a query serialization error. Most likely this occurred because another user or process attempted to change the same data that you were attempting to change. Please press Back and retry the transaction. After upgrading, QE couldn't find the serialization error happened anymore.
This change is now live. If there are any issues, do not reopen this bug. Instead, you should create a new bug and reference this bug.