Filtered Vector Search: What ACORN Fixes, and What Fixes ACORN
Summary
Qdrant’s article explains ACORN variants (ACORN-1 and ACORN-gamma) and the concept of Filterable HNSW to repair and augment nearest-neighbor graphs when metadata filters are applied. It compares four strategies across single and double filters on a one-million-point dataset, showing how additional index-time edges and search-time ACORN processing affect recall and latency. The piece provides practical guidance on when to enable ACORN, how the planner routes queries, and how to measure recall and latency for your own collection.