Disable approximate search in nearest neighbor blueprint

when ratio of candidates in the global filter is too low.

2 files changed, 3 insertions, 5 deletions

diff --git a/searchlib/src/vespa/searchlib/queryeval/nearest_neighbor_blueprint.cpp b/searchlib/src/vespa/searchlib/queryeval/nearest_neighbor_blueprint.cpp
index 3da20603e06..2cf6e7e29c4 100644
--- a/searchlib/src/vespa/searchlib/queryeval/nearest_neighbor_blueprint.cpp
+++ b/searchlib/src/vespa/searchlib/queryeval/nearest_neighbor_blueprint.cpp
@@ -59,7 +59,6 @@ NearestNeighborBlueprint::NearestNeighborBlueprint(const queryeval::FieldSpec& f
       _query_tensor(std::move(query_tensor)),
       _target_num_hits(target_num_hits),
       _approximate(approximate),
-      _use_brute_force(false),
       _explore_additional_hits(explore_additional_hits),
       _brute_force_limit(brute_force_limit),
       _fallback_dist_fun(),
@@ -101,13 +100,13 @@ NearestNeighborBlueprint::set_global_filter(const GlobalFilter &global_filter)
             LOG(debug, "set_global_filter getNumDocs: %u / max_hits %u", est_hits, max_hits);
             double max_hit_ratio = static_cast<double>(max_hits) / est_hits;
             if (max_hit_ratio < _brute_force_limit) {
-                _use_brute_force = true;
+                _approximate = false;
                 LOG(debug, "too many hits filtered out, using brute force implementation");
             } else {
                 est_hits = std::min(est_hits, max_hits);
             }
         }
-        if (!_use_brute_force) {
+        if (_approximate) {
             est_hits = std::min(est_hits, _target_num_hits);
             setEstimate(HitEstimate(est_hits, false));
             perform_top_k();
diff --git a/searchlib/src/vespa/searchlib/queryeval/nearest_neighbor_blueprint.h b/searchlib/src/vespa/searchlib/queryeval/nearest_neighbor_blueprint.h
index 8050d350af5..8656e5b4bf2 100644
--- a/searchlib/src/vespa/searchlib/queryeval/nearest_neighbor_blueprint.h
+++ b/searchlib/src/vespa/searchlib/queryeval/nearest_neighbor_blueprint.h
@@ -23,7 +23,6 @@ private:
     std::unique_ptr<vespalib::tensor::DenseTensorView> _query_tensor;
     uint32_t _target_num_hits;
     bool _approximate;
-    bool _use_brute_force;
     uint32_t _explore_additional_hits;
     double _brute_force_limit;
     search::tensor::DistanceFunction::UP _fallback_dist_fun;
@@ -45,7 +44,7 @@ public:
     const vespalib::tensor::DenseTensorView& get_query_tensor() const { return *_query_tensor; }
     uint32_t get_target_num_hits() const { return _target_num_hits; }
     void set_global_filter(const GlobalFilter &global_filter) override;
-    bool may_approximate() const { return _approximate && !_use_brute_force; }
+    bool may_approximate() const { return _approximate; }
 
     std::unique_ptr<SearchIterator> createLeafSearch(const search::fef::TermFieldMatchDataArray& tfmda,
                                                      bool strict) const override;