Score Variation Between Exact Search and ANN Search with PQ Index in Faiss Engine

[heemin32]

With the Faiss engine, if the number of filtered document IDs is less than k or the search results are fewer than k, it falls back to exact search. The scores obtained from exact search differ from those derived using the PQ index. As a result, the same document might have different scores depending on the segment it belongs to and the filter applied when the document is indexed with the PQ technique.

The variation in scores is typically minimal, which likely explains why no users have reported any issues related to this so far.