in my experience it’s pretty common to find big inverted indexes for text directly in the database - not necessarily large docs but certainly free text records in volume. using bm25 and unicode’s breakiterator is a very good way to build it. like putting lucene in the database basically - makes a lot of sense when the database is already large. places that bend over backwards to move search out of the db are usually trying to avoid having a very large db (and often end up with one anyway, getting the worst of both worlds)
They also end up with all the infrastructure and processes necessary to keep the external search system in sync, resync/reindex, pkey shipping back to their source of truth in queries, application-side joins and enrichment between both sources. It’s brutal.
Having everything in one place eliminates entire classes of development and especially operational problems.