Support specifying a distance metric for nearest neighbor search when not having a hnsw index.

This also changes the syntax in the sd file to specifying the distance metric in the attribute tag.

3 files changed, 12 insertions, 0 deletions

diff --git a/searchcommon/src/vespa/searchcommon/attribute/config.cpp b/searchcommon/src/vespa/searchcommon/attribute/config.cpp
index b4e05875820..7752baa603a 100644
--- a/searchcommon/src/vespa/searchcommon/attribute/config.cpp
+++ b/searchcommon/src/vespa/searchcommon/attribute/config.cpp
@@ -18,6 +18,7 @@ Config::Config() :
     _compactionStrategy(),
     _predicateParams(),
     _tensorType(vespalib::eval::ValueType::error_type()),
+    _distance_metric(DistanceMetric::Euclidean),
     _hnsw_index_params()
 {
 }
@@ -36,6 +37,7 @@ Config::Config(BasicType bt, CollectionType ct, bool fastSearch_, bool huge_)
       _compactionStrategy(),
       _predicateParams(),
       _tensorType(vespalib::eval::ValueType::error_type()),
+      _distance_metric(DistanceMetric::Euclidean),
       _hnsw_index_params()
 {
 }
@@ -63,6 +65,7 @@ Config::operator==(const Config &b) const
            _predicateParams == b._predicateParams &&
            (_basicType.type() != BasicType::Type::TENSOR ||
             _tensorType == b._tensorType) &&
+            _distance_metric == b._distance_metric &&
             _hnsw_index_params == b._hnsw_index_params;
 }
 
diff --git a/searchcommon/src/vespa/searchcommon/attribute/config.h b/searchcommon/src/vespa/searchcommon/attribute/config.h
index df5aa9e217a..822a4e4e028 100644
--- a/searchcommon/src/vespa/searchcommon/attribute/config.h
+++ b/searchcommon/src/vespa/searchcommon/attribute/config.h
@@ -9,6 +9,7 @@
 #include <vespa/searchcommon/common/compaction_strategy.h>
 #include <vespa/searchcommon/common/growstrategy.h>
 #include <vespa/eval/eval/value_type.h>
+#include <cassert>
 #include <optional>
 
 namespace search::attribute {
@@ -35,6 +36,7 @@ public:
     bool huge()                           const { return _huge; }
     const PredicateParams &predicateParams() const { return _predicateParams; }
     vespalib::eval::ValueType tensorType() const { return _tensorType; }
+    DistanceMetric distance_metric() const { return _distance_metric; }
     const std::optional<HnswIndexParams>& hnsw_index_params() const { return _hnsw_index_params; }
 
     /**
@@ -67,7 +69,12 @@ public:
         _tensorType = tensorType_in;
         return *this;
     }
+    Config& set_distance_metric(DistanceMetric value) {
+        _distance_metric = value;
+        return *this;
+    }
     Config& set_hnsw_index_params(const HnswIndexParams& params) {
+        assert(_distance_metric == params.distance_metric());
         _hnsw_index_params = params;
         return *this;
     }
@@ -122,6 +129,7 @@ private:
     CompactionStrategy _compactionStrategy;
     PredicateParams    _predicateParams;
     vespalib::eval::ValueType _tensorType;
+    DistanceMetric _distance_metric;
     std::optional<HnswIndexParams> _hnsw_index_params;
 };
 
diff --git a/searchcommon/src/vespa/searchcommon/attribute/hnsw_index_params.h b/searchcommon/src/vespa/searchcommon/attribute/hnsw_index_params.h
index 94d3fda49f3..3e3683ce60f 100644
--- a/searchcommon/src/vespa/searchcommon/attribute/hnsw_index_params.h
+++ b/searchcommon/src/vespa/searchcommon/attribute/hnsw_index_params.h
@@ -14,6 +14,7 @@ class HnswIndexParams {
 private:
     uint32_t _max_links_per_node;
     uint32_t _neighbors_to_explore_at_insert;
+    // This is always the same as in the attribute config, and is duplicated here to simplify usage.
     DistanceMetric _distance_metric;
 
 public: