Improve D&D registry normalization efficiency

internal/modules/dnd/normalize/locationregistry/normalizer.go

@@ -3,6 +3,7 @@ package locationregistry
 
 import (
 	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"reflect"
@@ -228,24 +229,44 @@ func normalizeRecord(input dnd.Location, order shared.SourceRefOrder) (dnd.Locat
 
 func exactDuplicateGroups(records []normalizedRecord) [][]int {
 	groups := make([][]int, 0, len(records))
+	groupPositions := make(map[string][]int, len(records))
 	for index, record := range records {
-		key := identity.ComparisonKey(record.location.Name)
-		found := false
-		for groupIndex, members := range groups {
-			first := records[members[0]]
-			if identity.ComparisonKey(first.location.Name) == key && reflect.DeepEqual(first.location.SourceRefs, record.location.SourceRefs) {
+		key := exactDuplicateKey(record.location)
+		comparisonName := identity.ComparisonKey(record.location.Name)
+		matched := false
+		for _, groupIndex := range groupPositions[key] {
+			first := records[groups[groupIndex][0]]
+			if identity.ComparisonKey(first.location.Name) == comparisonName && reflect.DeepEqual(first.location.SourceRefs, record.location.SourceRefs) {
 				groups[groupIndex] = append(groups[groupIndex], index)
-				found = true
+				matched = true
 				break
 			}
 		}
-		if !found {
-			groups = append(groups, []int{index})
+		if matched {
+			continue
 		}
+		groupPositions[key] = append(groupPositions[key], len(groups))
+		groups = append(groups, []int{index})
 	}
 	return groups
 }
 
+type duplicateKey struct {
+	ComparisonName string             `json:"comparison_name"`
+	SourceRefs     []source.SourceRef `json:"source_refs"`
+}
+
+func exactDuplicateKey(location dnd.Location) string {
+	encoded, err := json.Marshal(duplicateKey{
+		ComparisonName: identity.ComparisonKey(location.Name),
+		SourceRefs:     location.SourceRefs,
+	})
+	if err != nil {
+		panic("encode location duplicate key")
+	}
+	return string(encoded)
+}
+
 func cloneLocation(input dnd.Location) dnd.Location {
 	input.SourceRefs = cloneSourceRefs(input.SourceRefs)
 	return input