Index: src/main/java/org/apache/jackrabbit/oak/plugins/index/property/PropertyIndexEditor.java
===================================================================
--- src/main/java/org/apache/jackrabbit/oak/plugins/index/property/PropertyIndexEditor.java	(revision 1668276)
+++ src/main/java/org/apache/jackrabbit/oak/plugins/index/property/PropertyIndexEditor.java	(working copy)
@@ -258,35 +258,49 @@
             if (!beforeKeys.isEmpty() || !afterKeys.isEmpty()) {
                 updateCallback.indexUpdate();
                 NodeBuilder index = definition.child(INDEX_CONTENT_NODE_NAME);
-                getStrategy(keysToCheckForUniqueness != null).update(
-                        index, getPath(), beforeKeys, afterKeys);
                 if (keysToCheckForUniqueness != null) {
-                    keysToCheckForUniqueness.addAll(afterKeys);
+                    keysToCheckForUniqueness
+                    .addAll(filterFailingUniques(afterKeys, index, false));
                 }
+                getStrategy(keysToCheckForUniqueness != null).update(
+                        index, getPath(), beforeKeys, afterKeys);
             }
         }
 
         if (parent == null) {
             // make sure that the index node exist, even with no content
-            definition.child(INDEX_CONTENT_NODE_NAME);
+            NodeBuilder index = definition.child(INDEX_CONTENT_NODE_NAME);
 
             // check uniqueness constraints when leaving the root
             if (keysToCheckForUniqueness != null
                     && !keysToCheckForUniqueness.isEmpty()) {
-                NodeState indexMeta = definition.getNodeState();
-                IndexStoreStrategy s = getStrategy(true);
-                for (String key : keysToCheckForUniqueness) {
-                    if (s.count(indexMeta, singleton(key), 2) > 1) {
-                        String msg = String.format("Uniqueness constraint violated at path [%s] for one of the " +
-                                        "property in %s having value %s", getPath(), propertyNames, key);
-                        throw new CommitFailedException(
-                                CONSTRAINT, 30, msg);
-                    }
+                Set<String> failed = filterFailingUniques(
+                        keysToCheckForUniqueness, index, true);
+                if (!failed.isEmpty()) {
+                    String msg = String.format(
+                            "Uniqueness constraint violated at path [%s] for one of the "
+                                    + "property in %s having value %s",
+                            getPath(), propertyNames, failed.iterator().next());
+                    throw new CommitFailedException(CONSTRAINT, 30, msg);
                 }
             }
         }
     }
 
+    private Set<String> filterFailingUniques(Set<String> keys, NodeBuilder index, boolean fastStop) {
+        Set<String> doubles = newHashSet();
+        IndexStoreStrategy s = getStrategy(true);
+        for (String key : keys) {
+            if (s.exists(index, key)) {
+                doubles.add(key);
+                if (fastStop) {
+                    return doubles;
+                }
+            }
+        }
+        return doubles;
+    }
+
     private static boolean isTypeProperty(String name) {
         return JCR_PRIMARYTYPE.equals(name) || JCR_MIXINTYPES.equals(name);
     }
Index: src/main/java/org/apache/jackrabbit/oak/plugins/index/property/strategy/ContentMirrorStoreStrategy.java
===================================================================
--- src/main/java/org/apache/jackrabbit/oak/plugins/index/property/strategy/ContentMirrorStoreStrategy.java	(revision 1668276)
+++ src/main/java/org/apache/jackrabbit/oak/plugins/index/property/strategy/ContentMirrorStoreStrategy.java	(working copy)
@@ -460,4 +460,35 @@
             }
         }
     }
+
+    @Override
+    public boolean exists(NodeBuilder index, String key) {
+        NodeBuilder builder = index.getChildNode(key);
+        if (builder.exists()) {
+            // check for empty leaves
+
+            // Collect all builders along the given path
+            Deque<NodeBuilder> builders = newArrayDeque();
+            builders.addFirst(builder);
+
+            while (true) {
+                NodeBuilder b = builders.poll();
+                if (b == null) {
+                    return false;
+                }
+
+                for (String n : b.getChildNodeNames()) {
+                    NodeBuilder c = b.getChildNode(n);
+                    if (c.hasProperty("match")) {
+                        return true;
+                    } else {
+                        builders.push(c);
+                    }
+                }
+            }
+
+        } else {
+            return false;
+        }
+    }
 }
\ No newline at end of file
Index: src/main/java/org/apache/jackrabbit/oak/plugins/index/property/strategy/IndexStoreStrategy.java
===================================================================
--- src/main/java/org/apache/jackrabbit/oak/plugins/index/property/strategy/IndexStoreStrategy.java	(revision 1668276)
+++ src/main/java/org/apache/jackrabbit/oak/plugins/index/property/strategy/IndexStoreStrategy.java	(working copy)
@@ -39,7 +39,9 @@
     void update(
         NodeBuilder index, String path,
         Set<String> beforeKeys, Set<String> afterKeys);
-    
+
+    boolean exists(NodeBuilder index, String key);
+
     /**
      * Search for a given set of values.
      * 
Index: src/main/java/org/apache/jackrabbit/oak/plugins/index/property/strategy/UniqueEntryStoreStrategy.java
===================================================================
--- src/main/java/org/apache/jackrabbit/oak/plugins/index/property/strategy/UniqueEntryStoreStrategy.java	(revision 1668276)
+++ src/main/java/org/apache/jackrabbit/oak/plugins/index/property/strategy/UniqueEntryStoreStrategy.java	(working copy)
@@ -166,4 +166,9 @@
         return count;
     }
 
+    @Override
+    public boolean exists(NodeBuilder index, String key) {
+        return index.hasChildNode(key);
+    }
+
 }