Once the CheckUserUnionSelectQueryBuilder is implemented as part of T328988 Special:Investigate should use the new builder so that the results can be collected from all three new tables. This builder should only be used when SCHEMA_COMPAT_READ_NEW is set. It functions similarly to the SelectQueryBuilder and the query info can be exported from the builder using the pre-existing method in SelectQueryBuilder.
Progress:
- TimelineService
- CompareService