This impact is most severe in our Integration tests, which now take twice as long to run as before the PR was merged.
Prior to the merger of PR#2612, Travis CI builds/tests used to take roughly 25-30mins to complete. After the merger, Travis CI builds/tests consistently take over 45+mins to complete. As Travis CI kills any builds that take longer than 50mins, this means that some builds are killed before completion.
The Travis CI behaviors can be seen at: https://travis-ci.org/DSpace/DSpace/builds
PR#2612 was merged during Travis build #7495 (the first build that took much longer than 40mins). All prior Travis builds took <30mins.
I'm not sure myself why the performance is so much worse after this refactor. It could be the code itself, or it might be related to the change to the Solr Schema (changing resource type from int to String). Needs investigation.