3.0 dev convert l2sq score to l2 score for hnsw and ivfflat (#22543)

convert l2sq score to l2 score for hnsw and ivfflat

Approved by: @XuPeng-SH, @fengttt

Author: cpegeric

pkg/vectorindex/hnsw/search.go

@@ -18,6 +18,7 @@ import (
 	"errors"
 	"fmt"
 	"io"
+	"math"
 	"os"
 	"sync"
 	"sync/atomic"
@@ -265,6 +266,10 @@ func (s *HnswSearch) Search(proc *process.Process, anyquery any, rt vectorindex.
 			return nil, nil, moerr.NewInternalError(proc.Ctx, "heap return key is not int64")
 		}
 		reskeys = append(reskeys, sr.Id)
+		if s.Idxcfg.Usearch.Metric == usearch.L2sq {
+			// distance functino of L2Distance is l2sq so sqrt at the end
+			sr.Distance = math.Sqrt(sr.Distance)
+		}
 		resdistances = append(resdistances, sr.Distance)
 	}
 

pkg/vectorindex/ivfflat/search.go

@@ -17,6 +17,7 @@ package ivfflat
 import (
 	"context"
 	"fmt"
+	"math"
 	"strconv"
 	"sync"
 
@@ -284,6 +285,10 @@ func (idx *IvfflatSearchIndex[T]) Search(proc *process.Process, idxcfg vectorind
 			return nil, nil, moerr.NewInternalError(proc.Ctx, "ivf search: heap return key is not any")
 		}
 		resid = append(resid, sr.Id)
+		if metric.MetricType(idxcfg.Ivfflat.Metric) == metric.Metric_L2Distance {
+			// distance functino of L2Distance is l2sq so sqrt at the end
+			sr.Distance = math.Sqrt(sr.Distance)
+		}
 		resdist = append(resdist, sr.Distance)
 	}