The idea is to define a cutoff date that determines which historian is used for queries. Any history request that goes older than the cutoff would be served from the legacy historian (e.g., the SQL historian), while requests newer than the cutoff would be served from the new historian (e.g., Ignition Core historian).

This would make it much easier to migrate to a new historian while maintaining continuity, without needing to backfill all historical data immediately.

Example:

Query range ends before cutoff → read from legacy historian

Query range starts after cutoff → read from new historian

Query range spans the cutoff → automatically split and merge results from both historians