metabib_field_virtual_map

Maps between real (physically extracted) index definitions and virtual (target sync, no required extraction of its own) index definitions.

The virtual side may not extract any data of its own, but will collect data from all of the real fields. This reduces extraction (ingest) overhead by eliminating duplcated extraction, and allows for searching across novel combinations of fields, such as names used as either subjects or authors. By preserving this mapping rather than defining duplicate extractions, information about the originating, “real” index definitions can be used in interesting ways, such as highlighting in search results.