CODEWITHSUNDEEP
vespaapproximate-nn-searching
tourism
tourism

Reputation: 155

How filtered document list look up work in nearest neighbour search prefiltering

In pre-filter based ANN, once we have list of documents after applying pre-filter, vespa starts hsnw algorithm to find nearest neighbours. In hsnw algorithm, vespa starts with a node and look for the neighbours which are present in pre-filter list, How search of neighbour in document list is implemented in vespa ? it's linear search or hashing ?

Upvotes: 2

Views: 313

Answers (1)

Jo Kristian Bergum
Jo Kristian Bergum

Reputation: 3184

This blog post has an excellent overview of how Vespa combines filters with HNSW search https://blog.vespa.ai/constrained-approximate-nearest-neighbor-search/.

In pre-filter case, the resulting "allow" document list is a bitvector, and the lookup is O(1).

Upvotes: 2

Related Questions