# UNDF: UNDF-2026-000000174
--- a/src/main/java/org/apache/ibatis/builder/ResultMappingConstructorResolver.java
+++ b/src/main/java/org/apache/ibatis/builder/ResultMappingConstructorResolver.java
@@ -268,11 +268,18 @@ class ResultMappingConstructorResolver {

 	private static void sortConstructorMappings(ConstructorMetaInfo matchingConstructorInfo,
 			List<ResultMapping> resultMappings) {
-		final List<String> orderedConstructorParameters =
-				new ArrayList<>(matchingConstructorInfo.constructorArgs.keySet());
+		// mybatis-0001 fix: pre-build an index Map<String,Integer> to replace
+		// ArrayList.indexOf() calls inside the sort comparator.
+		// Previously: orderedConstructorParameters was an ArrayList<String>; the sort
+		// comparator called indexOf(o1.getProperty()) and indexOf(o2.getProperty()), each
+		// O(P) where P = number of constructor parameters.  A comparison sort invokes the
+		// comparator O(N log N) times (N = resultMappings.size()), giving O(N*P*log N)
+		// total.  With a Map<String,Integer> lookup the comparator is O(1), reducing to
+		// O(N log N) — a speedup of O(P) per sort.
+		final Map<String, Integer> paramIndex = new HashMap<>();
+		int idx = 0;
+		for (String paramName : matchingConstructorInfo.constructorArgs.keySet()) {
+			paramIndex.put(paramName, idx++);
+		}
 		resultMappings.sort((o1, o2) -> {
-			int paramIdx1 = orderedConstructorParameters.indexOf(o1.getProperty());
-			int paramIdx2 = orderedConstructorParameters.indexOf(o2.getProperty());
+			int paramIdx1 = paramIndex.getOrDefault(o1.getProperty(), -1);
+			int paramIdx2 = paramIndex.getOrDefault(o2.getProperty(), -1);
 			return paramIdx1 - paramIdx2;
 		});
 	}