better control of failure in node seek of kelondroTree

git-svn-id: https://svn.berlios.de/svnroot/repos/yacy/trunk@2686 6c8d7289-2bf4-0310-a012-ef5d649a1542

source/de/anomic/kelondro/kelondroTree.java

@@ -270,7 +270,10 @@ public class kelondroTree extends kelondroRecords implements kelondroIndex {
         private Node thenode, parentnode;
         private boolean found; // property if node was found
         private byte child; // -1: left child; 0: root node; 1: right child
+
+        // temporary variables
         private Handle thisHandle;
+        byte[] keybuffer;
         
         protected Search() {
         }
@@ -282,6 +285,8 @@ public class kelondroTree extends kelondroRecords implements kelondroIndex {
             thisHandle = getHandle(root);
             parentnode = null;
             if (key == null) {
+                throw new kelondroException("startet search process with key == null");
+                /*
                 child = 0;
                 if (thisHandle == null) {
                     thenode = null;
@@ -290,13 +295,15 @@ public class kelondroTree extends kelondroRecords implements kelondroIndex {
                     thenode = getNode(thisHandle, null, 0);
                     found = true;
                 }
-            } else {
+                return;
+                */
+            }
             thenode = null;
             child = 0;
             found = false;
             int c;
-                byte[] k;
-                TreeSet visitedNodeKeys = new TreeSet(loopDetectionOrder); // to detect loops
+            
+            TreeMap visitedNodeKeys = new TreeMap(loopDetectionOrder); // to detect loops
             // System.out.println("Starting Compare Loop in Database " + filename); // debug
             while (thisHandle != null) {
                 try {
@@ -307,15 +314,25 @@ public class kelondroTree extends kelondroRecords implements kelondroIndex {
                     found = false;
                     return;
                 }
-                    if (thenode == null) {
-                        throw new kelondroException(filename, "kelondroTree.Search.process: thenode==null");
-                    }
-                    k = thenode.getKey();
-                    if (k == null) {
+                if (thenode == null) throw new kelondroException(filename, "kelondroTree.Search.process: thenode==null");
+
+                keybuffer = thenode.getKey();
+                if (keybuffer == null) {
+                    // this is an error. distinguish two cases:
+                    // 1. thenode is a leaf node. Then this error can be fixed if we can consider this node as a good node to be replaced with a new value
+                    // 2. thenode is not a leaf node. An exception must be thrown
+                    if ((thenode.getOHHandle(leftchild) == null) && (thenode.getOHHandle(rightchild) == null)) {
+                        // case 1: recover
+                        deleteNode(thisHandle);
+                        thenode = parentnode;
                         found = false;
                         return;
+                    } else {
+                        // case 2: fail
+                        throw new kelondroException("found key during search process with key == null");
                     }
-                    if (visitedNodeKeys.contains(k)) {
+                }
+                if (visitedNodeKeys.containsKey(keybuffer)) {
                     // we have loops in the database.
                     // to fix this, all affected nodes must be patched
                     thenode.setOHByte(magic, (byte) 1);
@@ -329,7 +346,7 @@ public class kelondroTree extends kelondroRecords implements kelondroIndex {
                     return;
                 }
                 // System.out.println("Comparing key = '" + new String(key) + "' with '" + otherkey + "':"); // debug
-                        c = objectOrder.compare(key, k);
+                c = objectOrder.compare(key, keybuffer);
                 // System.out.println(c); // debug
                 if (c == 0) {
                     found = true;
@@ -342,8 +359,7 @@ public class kelondroTree extends kelondroRecords implements kelondroIndex {
                     child = 1;
                     thisHandle = thenode.getOHHandle(rightchild);
                 }
-                        visitedNodeKeys.add(k);
-                }
+                visitedNodeKeys.put(keybuffer, null);
             }
             // System.out.println("DEBUG: search for " + new String(key) + " ended with status=" + ((found) ? "found" : "not-found") + ", node=" + ((thenode == null) ? "NULL" : thenode.toString()) + ", parent=" + ((parentnode == null) ? "NULL" : parentnode.toString()));
             // we reached a node where we must insert the new value
@@ -442,10 +458,10 @@ public class kelondroTree extends kelondroRecords implements kelondroIndex {
                 // check consistency and link new node to parent node
                 byte parentBalance;
                 if (writeSearchObj.isLeft()) {
-                    if (parentNode.getOHHandle(leftchild) != null) throw new kelondroException(filename, "tried to create leftchild node twice");
+                    if (parentNode.getOHHandle(leftchild) != null) throw new kelondroException(filename, "tried to create leftchild node twice. parent=" + new String(parentNode.getKey()) + ", leftchild=" + new String(new Node(parentNode.getOHHandle(leftchild), (Node) null, 0).getKey()));
                     parentNode.setOHHandle(leftchild, theNode.handle());
                 } else if (writeSearchObj.isRight()) {
-                    if (parentNode.getOHHandle(rightchild) != null) throw new kelondroException(filename, "tried to create rightchild node twice");
+                    if (parentNode.getOHHandle(rightchild) != null) throw new kelondroException(filename, "tried to create rightchild node twice. parent=" + new String(parentNode.getKey()) + ", rightchild=" + new String(new Node(parentNode.getOHHandle(rightchild), (Node) null, 0).getKey()));
                     parentNode.setOHHandle(rightchild, theNode.handle());
                 } else {
                     throw new kelondroException(filename, "neither left nor right child");