Would love to see a system that blends cheap lexical (Fulltext Search) or semantic/vector search using SQLite and chooses the best approach given the input.
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Having the FTS engine provide a google-style snippet of the most relevant document chunk is the holy grail for RAG applications. Lucene does this kind of thing better than anyone else:
https://lucene.apache.org/core/8_0_0/highlighter/org/apache/...
It is also very easy to customize this engine and align the document tokenization & indexing concerns with your specific retrieval scenarios.