Most of the attention on full-text search goes to BM25. Query a part number, get that part number back first.
A query like "why does PROD-001 overheat under load" has a literal string and a question in it though. That's where text-match filtering comes in. It narrows results to the documents that contain the literal string, and semantic search ranks what's left, all from one index.
Full-text search is GA in Pinecone Database, text-match filtering included.
đ