### Eclipse Workspace Patch 1.0
#P oak-core
Index: src/test/java/org/apache/jackrabbit/oak/plugins/index/nodetype/NodeTypeIndexTest.java
===================================================================
--- src/test/java/org/apache/jackrabbit/oak/plugins/index/nodetype/NodeTypeIndexTest.java	(revision 1604905)
+++ src/test/java/org/apache/jackrabbit/oak/plugins/index/nodetype/NodeTypeIndexTest.java	(working copy)
@@ -72,6 +72,9 @@
 
         // remove "rep:security" as it interferes with tests
         root.getChildNode("rep:security").remove();
+        
+        // remove "entryCount", so the node type index cost is not fixed
+        root.getChildNode("oak:index").getChildNode("nodetype").removeProperty("entryCount");
 
         addFolder(root, "folder-1");
         addFolder(root, "folder-2");
Index: src/main/java/org/apache/jackrabbit/oak/plugins/index/IndexConstants.java
===================================================================
--- src/main/java/org/apache/jackrabbit/oak/plugins/index/IndexConstants.java	(revision 1604905)
+++ src/main/java/org/apache/jackrabbit/oak/plugins/index/IndexConstants.java	(working copy)
@@ -39,6 +39,8 @@
 
     String ENTRY_COUNT_PROPERTY_NAME = "entryCount";
 
+    String KEY_COUNT_PROPERTY_NAME = "keyCount";
+
     /**
      * Marks a unique property index.
      */
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 1604905)
+++ src/main/java/org/apache/jackrabbit/oak/plugins/index/property/strategy/ContentMirrorStoreStrategy.java	(working copy)
@@ -19,6 +19,7 @@
 import static com.google.common.collect.Queues.newArrayDeque;
 import static org.apache.jackrabbit.oak.plugins.index.IndexConstants.INDEX_CONTENT_NODE_NAME;
 import static org.apache.jackrabbit.oak.plugins.index.IndexConstants.ENTRY_COUNT_PROPERTY_NAME;
+import static org.apache.jackrabbit.oak.plugins.index.IndexConstants.KEY_COUNT_PROPERTY_NAME;
 
 import java.util.Deque;
 import java.util.Iterator;
@@ -177,6 +178,20 @@
             if (size == 0) {
                 return 0;
             }
+            PropertyState ec = indexMeta.getProperty(ENTRY_COUNT_PROPERTY_NAME);       
+            if (ec != null) {
+                long entryCount = ec.getValue(Type.LONG);
+                long keyCount = entryCount / 10000;
+                ec = indexMeta.getProperty(KEY_COUNT_PROPERTY_NAME);
+                if (ec != null) {
+                    keyCount = ec.getValue(Type.LONG);
+                }
+                // cast to double to avoid overflow 
+                // (entryCount could be Long.MAX_VALUE)
+                // the cost is not multiplied by the size, 
+                // otherwise the traversing index might be used
+                return (long) ((double) entryCount / keyCount) + size;
+            }
             max = Math.max(10, max / size);
             int i = 0;
             for (String p : values) {
#P oak-jcr
Index: src/test/java/org/apache/jackrabbit/oak/jcr/query/QueryPlanTest.java
===================================================================
--- src/test/java/org/apache/jackrabbit/oak/jcr/query/QueryPlanTest.java	(revision 1604905)
+++ src/test/java/org/apache/jackrabbit/oak/jcr/query/QueryPlanTest.java	(working copy)
@@ -46,6 +46,55 @@
     }
     
     @Test
+    // OAK-1902
+    public void propertyIndexVersusNodeTypeIndex() throws Exception {
+        Session session = getAdminSession();
+        Node nt = session.getRootNode().getNode("oak:index").getNode("nodetype");
+        nt.setProperty("entryCount", Long.MAX_VALUE);
+        QueryManager qm = session.getWorkspace().getQueryManager();
+        Node testRootNode = session.getRootNode().addNode("testroot");
+        for (int i = 0; i < 100; i++) {
+            Node n = testRootNode.addNode("n" + i, "oak:Unstructured");
+            n.addMixin("mix:referenceable");
+        }
+        session.save();
+       
+        Query q;
+        QueryResult result;
+        RowIterator it;
+
+        String xpath = "/jcr:root/a/b/c/d/e/f/g/h/i/j/k/element(*, oak:Unstructured)";
+        q = qm.createQuery("explain " + xpath, "xpath");
+        result = q.execute();
+        it = result.getRows();
+        assertTrue(it.hasNext());
+        String plan = it.nextRow().getValue("plan").getString();
+        // System.out.println("plan: " + plan);
+        // should use the node type index
+        assertEquals("[oak:Unstructured] as [a] " + 
+                "/* Filter(query=explain select [jcr:path], [jcr:score], * " + 
+                "from [oak:Unstructured] as a " + 
+                "where ischildnode(a, '/a/b/c/d/e/f/g/h/i/j/k') " + 
+                "/* xpath: /jcr:root/a/b/c/d/e/f/g/h/i/j/k/element(*, oak:Unstructured) */" + 
+                ", path=/a/b/c/d/e/f/g/h/i/j/k/*) where " + 
+                "ischildnode([a], [/a/b/c/d/e/f/g/h/i/j/k]) */", 
+                plan);
+
+        String xpath2 = "/jcr:root/a/b/c/d/e/f/g/h/i/j/k/element(*, oak:Unstructured)[@jcr:uuid]";
+        q = qm.createQuery("explain " + xpath2 + "", "xpath");
+        result = q.execute();
+        it = result.getRows();
+        assertTrue(it.hasNext());
+        plan = it.nextRow().getValue("plan").getString();
+        // System.out.println("plan: " + plan);
+        // should use the index on "jcr:uuid"
+        assertEquals("[oak:Unstructured] as [a] " + 
+                "/* property jcr:uuid where ([a].[jcr:uuid] is not null) " + 
+                "and (ischildnode([a], [/a/b/c/d/e/f/g/h/i/j/k])) */", 
+                plan);
+    }     
+    
+    @Test
     // OAK-1903
     public void propertyEqualsVersusPropertyNotNull() throws Exception {
         Session session = getAdminSession();