001    /**
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *      http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.kahadb.index;
018    
019    import java.io.DataInput;
020    import java.io.DataOutput;
021    import java.io.IOException;
022    import java.io.PrintWriter;
023    import java.util.Arrays;
024    import java.util.Iterator;
025    import java.util.Map;
026    import java.util.NoSuchElementException;
027    import java.util.Map.Entry;
028    
029    import org.apache.kahadb.index.BTreeIndex.Prefixer;
030    import org.apache.kahadb.page.Page;
031    import org.apache.kahadb.page.Transaction;
032    import org.apache.kahadb.util.VariableMarshaller;
033    
034    
035    /**
036     * The BTreeNode class represents a node in the BTree object graph.  It is stored in 
037     * one Page of a PageFile.
038     */
039    public final class BTreeNode<Key,Value> {
040    
041        // The index that this node is part of.
042        private final BTreeIndex<Key,Value> index;
043        // The parent node or null if this is the root node of the BTree
044        private BTreeNode<Key,Value> parent;
045        // The page associated with this node
046        private Page<BTreeNode<Key,Value>> page;
047        
048        // Order list of keys in the node
049        private Key[] keys;
050        // Values associated with the Keys. Null if this is a branch node.
051        private Value[] values;
052        // nodeId pointers to children BTreeNodes. Null if this is a leaf node.
053        private long[] children;
054        // The next leaf node after this one.  Used for fast iteration of the entries.
055        private long next = -1;
056        
057        private final class KeyValueEntry implements Map.Entry<Key, Value> {
058            private final Key key;
059            private final Value value;
060    
061            public KeyValueEntry(Key key, Value value) {
062                this.key = key;
063                this.value = value;
064            }
065    
066            public Key getKey() {
067                return key;
068            }
069    
070            public Value getValue() {
071                return value;
072            }
073    
074            public Value setValue(Value value) {
075                throw new UnsupportedOperationException();
076            }
077    
078        }
079    
080        private final class BTreeIterator implements Iterator<Map.Entry<Key, Value>> {
081            
082            private final Transaction tx;
083            BTreeNode<Key,Value> current;
084            int nextIndex;
085            Map.Entry<Key,Value> nextEntry;
086    
087            private BTreeIterator(Transaction tx, BTreeNode<Key,Value> current, int nextIndex) {
088                this.tx = tx;
089                this.current = current;
090                this.nextIndex=nextIndex;
091            }
092    
093            synchronized private void findNextPage() {
094                if( nextEntry!=null ) {
095                    return;
096                }
097                
098                try {
099                    while( current!=null ) {
100                        if( nextIndex >= current.keys.length ) {
101                            // we need to roll to the next leaf..
102                            if( current.next >= 0 ) {
103                                current = index.loadNode(tx, current.next, null);
104                                assert !current.isBranch() : "Should have linked to the next leaf node.";
105                                nextIndex=0;
106                            } else {
107                                break;
108                            }
109                        }  else {
110                            nextEntry = new KeyValueEntry(current.keys[nextIndex], current.values[nextIndex]);
111                            nextIndex++;
112                            break;
113                        }
114                        
115                    }
116                } catch (IOException e) {
117                }
118            }
119    
120            public boolean hasNext() {
121                findNextPage();
122                return nextEntry !=null;
123            }
124    
125            public Entry<Key, Value> next() {
126                findNextPage(); 
127                if( nextEntry !=null ) {
128                    Entry<Key, Value> lastEntry = nextEntry;
129                    nextEntry=null;
130                    return lastEntry;
131                } else {
132                    throw new NoSuchElementException();
133                }
134            }
135    
136            public void remove() {
137                throw new UnsupportedOperationException();
138            }
139        }
140    
141        /**
142         * The Marshaller is used to store and load the data in the BTreeNode into a Page.
143         *  
144         * @param <Key>
145         * @param <Value>
146         */
147        static public class Marshaller<Key,Value> extends VariableMarshaller<BTreeNode<Key,Value>> {
148            private final BTreeIndex<Key,Value> index;
149            
150            public Marshaller(BTreeIndex<Key,Value> index) {
151                this.index = index;
152            }
153    
154            public void writePayload(BTreeNode<Key,Value> node, DataOutput os) throws IOException {
155                // Write the keys
156                short count = (short)node.keys.length; // cast may truncate value...
157                if( count != node.keys.length ) {
158                    throw new IOException("Too many keys");
159                }
160                
161                os.writeShort(count);
162                for (int i = 0; i < node.keys.length; i++) {
163                    index.getKeyMarshaller().writePayload(node.keys[i], os);
164                }
165                
166                if( node.isBranch() ) {
167                    // If this is a branch...
168                    os.writeBoolean(true);
169                    for (int i = 0; i < count+1; i++) {
170                        os.writeLong(node.children[i]);
171                    }
172                    
173                } else {
174                    // If this is a leaf
175                    os.writeBoolean(false);
176                    for (int i = 0; i < count; i++) {
177                        index.getValueMarshaller().writePayload(node.values[i], os);
178                    }
179                    os.writeLong(node.next);
180                }
181            }
182    
183            @SuppressWarnings("unchecked")
184            public BTreeNode<Key,Value> readPayload(DataInput is) throws IOException {
185                BTreeNode<Key,Value>  node = new BTreeNode<Key,Value>(index);
186                int count = is.readShort();
187                
188                node.keys = (Key[])new Object[count];
189                for (int i = 0; i < count; i++) {
190                    node.keys[i] = index.getKeyMarshaller().readPayload(is);
191                }
192                
193                if( is.readBoolean() ) {
194                    node.children = new long[count+1];
195                    for (int i = 0; i < count+1; i++) {
196                        node.children[i] = is.readLong();
197                    }
198                } else {
199                    node.values = (Value[])new Object[count];
200                    for (int i = 0; i < count; i++) {
201                        node.values[i] = index.getValueMarshaller().readPayload(is);
202                    }
203                    node.next = is.readLong();
204                }
205                return node;
206            }
207        }
208    
209        public BTreeNode(BTreeIndex<Key,Value> index) {
210            this.index = index;
211        }
212        
213        public void setEmpty() {
214            setLeafData(createKeyArray(0), createValueArray(0));
215        }
216        
217    
218        /**
219         * Internal (to the BTreeNode) method. Because this method is called only by
220         * BTreeNode itself, no synchronization done inside of this method.
221         * @throws IOException 
222         */
223        private BTreeNode<Key,Value> getChild(Transaction tx, int idx) throws IOException {
224            if (isBranch() && idx >= 0 && idx < children.length) {
225                BTreeNode<Key, Value> result = this.index.loadNode(tx, children[idx], this);
226                return result;
227            } else {
228                return null;
229            }
230        }
231    
232    
233        /**
234         * Returns the right most leaf from the current btree graph.
235         * @throws IOException
236         */
237        private BTreeNode<Key,Value> getRightLeaf(Transaction tx) throws IOException {
238            BTreeNode<Key,Value> cur = this;
239            while(cur.isBranch()) {
240                cur = cur.getChild(tx, cur.keys.length);
241            }
242            return cur;
243        }
244    
245        /**
246         * Returns the left most leaf from the current btree graph.
247         * @throws IOException
248         */
249        private BTreeNode<Key,Value> getLeftLeaf(Transaction tx) throws IOException {
250            BTreeNode<Key,Value> cur = this;
251            while(cur.isBranch()) {
252                cur = cur.getChild(tx, 0);
253            }
254            return cur;
255        }
256    
257        /**
258         * Returns the left most leaf from the current btree graph.
259         * @throws IOException
260         */
261        private BTreeNode<Key,Value> getLeftPeer(Transaction tx, BTreeNode<Key,Value> x) throws IOException {
262            BTreeNode<Key,Value> cur = x;
263            while( cur.parent !=null ) {
264                if( cur.parent.children[0] == cur.getPageId() ) {
265                    cur = cur.parent;
266                } else {
267                    for( int i=0; i < cur.parent.children.length; i ++) {
268                        if( cur.parent.children[i]==cur.getPageId() ) {
269                            return  cur.parent.getChild(tx, i-1);
270                        }
271                    }
272                    throw new AssertionError("page "+x+" was decendent of "+cur.getPageId());
273                }
274            }
275            return null;
276        }
277    
278        public Value remove(Transaction tx, Key key) throws IOException {
279    
280            if(isBranch()) {
281                int idx = Arrays.binarySearch(keys, key);
282                idx = idx < 0 ? -(idx + 1) : idx + 1;
283                BTreeNode<Key, Value> child = getChild(tx, idx);
284                if( child.getPageId() == index.getPageId() ) {
285                    throw new IOException("BTree corrupted: Cylce detected.");
286                }
287                Value rc = child.remove(tx, key);
288                
289                // child node is now empty.. remove it from the branch node.
290                if( child.keys.length == 0 ) {
291                    
292                    // If the child node is a branch, promote
293                    if( child.isBranch() ) {
294                        // This is cause branches are never really empty.. they just go down to 1 child..
295                        children[idx] = child.children[0];
296                    } else {
297                        
298                        // The child was a leaf. Then we need to actually remove it from this branch node..
299                        // and relink the previous leaf to skip to the next leaf.
300    
301                        BTreeNode<Key, Value> previousLeaf = null;
302                        if( idx > 0 ) {
303                            // easy if we this node hold the previous child.
304                            previousLeaf = getChild(tx, idx-1).getRightLeaf(tx);
305                        } else {
306                            // less easy if we need to go to the parent to find the previous child.
307                            BTreeNode<Key, Value> lp = getLeftPeer(tx, this);
308                            if( lp!=null ) {
309                                previousLeaf = lp.getRightLeaf(tx);
310                            }
311                            // lp will be null if there was no previous child.
312                        }
313    
314                        if( previousLeaf !=null ) {
315                            previousLeaf.next = child.next;
316                            index.storeNode(tx, previousLeaf, true);
317                        }
318    
319                        if( idx < children.length-1 ) {
320                            // Delete it and key to the right.
321                            setBranchData(arrayDelete(keys, idx), arrayDelete(children, idx));
322                        } else {
323                            // It was the last child.. Then delete it and key to the left
324                            setBranchData(arrayDelete(keys, idx-1), arrayDelete(children, idx));
325                        }
326                        
327                        // If we are the root node, and only have 1 child left.  Then 
328                        // make the root be the leaf node.
329                        if( children.length == 1 && parent==null ) {
330                            child = getChild(tx, 0);
331                            keys = child.keys;
332                            children = child.children;
333                            values = child.values;
334                            // free up the page..
335                            tx.free(child.getPage());
336                        }
337                        
338                    }
339                    index.storeNode(tx, this, true);
340                }
341                
342                return rc;
343            } else {
344                int idx = Arrays.binarySearch(keys, key);
345                if (idx < 0) {
346                    return null;
347                } else {
348                    Value oldValue = values[idx];
349                    setLeafData(arrayDelete(keys, idx), arrayDelete(values, idx));
350                    
351                    if( keys.length==0 && parent!=null) {
352                        tx.free(getPage());
353                    } else {
354                        index.storeNode(tx, this, true);
355                    }
356                    
357                    return oldValue;
358                }
359            }
360        }
361    
362        public Value put(Transaction tx, Key key, Value value) throws IOException {
363            if (key == null) {
364                throw new IllegalArgumentException("Key cannot be null");
365            }
366    
367            if( isBranch() ) {
368                return getLeafNode(tx, this, key).put(tx, key, value);
369            } else {
370                int idx = Arrays.binarySearch(keys, key);
371                
372                Value oldValue=null;
373                if (idx >= 0) {
374                    // Key was found... Overwrite
375                    oldValue = values[idx];
376                    values[idx] = value;
377                    setLeafData(keys, values);
378                } else {
379                    // Key was not found, Insert it
380                    idx = -(idx + 1);
381                    setLeafData(arrayInsert(keys, key, idx), arrayInsert(values, value, idx));
382                }
383                
384                try {
385                    index.storeNode(tx, this, allowOverflow());
386                } catch ( Transaction.PageOverflowIOException e ) {
387                    // If we get an overflow 
388                    split(tx);
389                }
390                
391                return oldValue;
392            }
393        }
394    
395        private void promoteValue(Transaction tx, Key key, long nodeId) throws IOException {
396    
397            int idx = Arrays.binarySearch(keys, key);
398            idx = idx < 0 ? -(idx + 1) : idx + 1;
399            setBranchData(arrayInsert(keys, key, idx), arrayInsert(children, nodeId, idx + 1));
400    
401            try {
402                index.storeNode(tx, this, allowOverflow());
403            } catch ( Transaction.PageOverflowIOException e ) {
404                split(tx);
405            }
406    
407        }
408    
409        /**
410         * Internal to the BTreeNode method
411         */
412        private void split(Transaction tx) throws IOException {
413            Key[] leftKeys;
414            Key[] rightKeys;
415            Value[] leftValues=null;
416            Value[] rightValues=null;
417            long[] leftChildren=null;
418            long[] rightChildren=null;
419            Key separator;
420    
421            int vc = keys.length;
422            int pivot = vc / 2;
423    
424            // Split the node into two nodes
425            if( isBranch() ) {
426    
427                leftKeys = createKeyArray(pivot);
428                leftChildren = new long[leftKeys.length + 1];
429                rightKeys = createKeyArray(vc - (pivot + 1));
430                rightChildren = new long[rightKeys.length + 1];
431    
432                System.arraycopy(keys, 0, leftKeys, 0, leftKeys.length);
433                System.arraycopy(children, 0, leftChildren, 0, leftChildren.length);
434                System.arraycopy(keys, leftKeys.length + 1, rightKeys, 0, rightKeys.length);
435                System.arraycopy(children, leftChildren.length, rightChildren, 0, rightChildren.length);
436    
437                // Is it a Simple Prefix BTree??
438                Prefixer<Key> prefixer = index.getPrefixer();
439                if(prefixer!=null) {
440                    separator = prefixer.getSimplePrefix(leftKeys[leftKeys.length - 1], rightKeys[0]);
441                } else {
442                    separator = keys[leftKeys.length];
443                }
444                    
445                
446            } else {
447    
448                leftKeys = createKeyArray(pivot);
449                leftValues = createValueArray(leftKeys.length);
450                rightKeys = createKeyArray(vc - pivot);
451                rightValues = createValueArray(rightKeys.length);
452    
453                System.arraycopy(keys, 0, leftKeys, 0, leftKeys.length);
454                System.arraycopy(values, 0, leftValues, 0, leftValues.length);
455                System.arraycopy(keys, leftKeys.length, rightKeys, 0, rightKeys.length);
456                System.arraycopy(values, leftValues.length, rightValues, 0, rightValues.length);
457    
458                // separator = getSeparator(leftVals[leftVals.length - 1],
459                // rightVals[0]);
460                separator = rightKeys[0];
461    
462            }
463    
464            // Promote the pivot to the parent branch
465            if (parent == null) {
466                
467                // This can only happen if this is the root
468                BTreeNode<Key,Value> rNode = this.index.createNode(tx, this);
469                BTreeNode<Key,Value> lNode = this.index.createNode(tx, this);
470    
471                if( isBranch() ) {
472                    rNode.setBranchData(rightKeys, rightChildren);
473                    lNode.setBranchData(leftKeys, leftChildren);
474                } else {
475                    rNode.setLeafData(rightKeys, rightValues);
476                    lNode.setLeafData(leftKeys, leftValues);
477                    lNode.setNext(rNode.getPageId());
478                }
479    
480                Key[] v = createKeyArray(1);
481                v[0]=separator;
482                setBranchData(v, new long[] { lNode.getPageId(), rNode.getPageId() });
483    
484                index.storeNode(tx, this, true);
485                index.storeNode(tx, rNode, true);
486                index.storeNode(tx, lNode, true);
487                
488            } else {
489                BTreeNode<Key,Value> rNode = this.index.createNode(tx, parent);
490                
491                if( isBranch() ) {
492                    setBranchData(leftKeys, leftChildren);
493                    rNode.setBranchData(rightKeys, rightChildren);
494                } else {
495                    rNode.setNext(next);
496                    next = rNode.getPageId();
497                    setLeafData(leftKeys, leftValues);
498                    rNode.setLeafData(rightKeys, rightValues);
499                }
500    
501                index.storeNode(tx, this, true);
502                index.storeNode(tx, rNode, true);
503                parent.promoteValue(tx, separator, rNode.getPageId());
504            }
505        }
506    
507        public void printStructure(Transaction tx, PrintWriter out, String prefix) throws IOException {
508            if( prefix.length()>0 && parent == null ) {
509                throw new IllegalStateException("Cycle back to root node detected.");
510            }
511            
512            if( isBranch() ) {
513                for(int i=0 ; i < children.length; i++) {
514                    BTreeNode<Key, Value> child = getChild(tx, i);
515                    if( i == children.length-1) {
516                        out.println(prefix+"\\- "+child.getPageId()+(child.isBranch()?" ("+child.children.length+")":""));
517                        child.printStructure(tx, out, prefix+"   ");
518                    } else {
519                        out.println(prefix+"|- "+child.getPageId()+(child.isBranch()?" ("+child.children.length+")":"")+" : "+keys[i]);
520                        child.printStructure(tx, out, prefix+"   ");
521                    }
522                }
523            }
524        }
525        
526        
527        public int getMinLeafDepth(Transaction tx, int depth) throws IOException {
528            depth++;
529            if( isBranch() ) {
530                int min = Integer.MAX_VALUE;
531                for(int i=0 ; i < children.length; i++) {
532                    min = Math.min(min, getChild(tx, i).getMinLeafDepth(tx, depth));
533                }
534                return min;
535            } else {
536    //            print(depth*2, "- "+page.getPageId());
537                return depth;
538            }
539        }
540    
541        public int getMaxLeafDepth(Transaction tx, int depth) throws IOException {
542            depth++;
543            if( isBranch() ) {
544                int v = 0;
545                for(int i=0 ; i < children.length; i++) {
546                    v = Math.max(v, getChild(tx, i).getMaxLeafDepth(tx, depth));
547                }
548                depth = v;
549            } 
550            return depth;
551        }
552    
553        public Value get(Transaction tx, Key key) throws IOException {
554            if (key == null) {
555                throw new IllegalArgumentException("Key cannot be null");
556            }
557            if( isBranch() ) {
558                return getLeafNode(tx, this, key).get(tx, key);
559            } else {
560                int idx = Arrays.binarySearch(keys, key);
561                if (idx < 0) {
562                    return null;
563                } else {
564                    return values[idx];
565                }
566            }
567        }
568        
569        public boolean isEmpty(final Transaction tx) throws IOException {
570            return keys.length==0;
571        }
572    
573        public void visit(Transaction tx, BTreeVisitor<Key, Value> visitor) throws IOException {
574            if (visitor == null) {
575                throw new IllegalArgumentException("Visitor cannot be null");
576            }
577            if( isBranch() ) {
578                for(int i=0; i < this.children.length; i++) {
579                    Key key1 = null;
580                    if( i!=0 ) {
581                        key1 = keys[i-1];
582                    }
583                    Key key2 = null;
584                    if( i!=this.children.length-1 ) {
585                        key2 = keys[i];
586                    }
587                    if( visitor.isInterestedInKeysBetween(key1, key2) ) {
588                        BTreeNode<Key, Value> child = getChild(tx, i);
589                        child.visit(tx, visitor);
590                    }
591                }
592            } else {
593                visitor.visit(Arrays.asList(keys), Arrays.asList(values));
594            }
595        }
596        
597        public Map.Entry<Key,Value> getFirst(Transaction tx) throws IOException {
598            BTreeNode<Key, Value> node = this;
599            while( node .isBranch() ) {
600                node = node.getChild(tx, 0);
601            }
602            if( node.values.length>0 ) {
603                return new KeyValueEntry(node.keys[0], node.values[0]);
604            } else {
605                return null;
606            }
607        }
608    
609        public Map.Entry<Key,Value> getLast(Transaction tx) throws IOException {
610            BTreeNode<Key, Value> node = this;
611            while( node.isBranch() ) {
612                node = node.getChild(tx, node.children.length-1);
613            }
614            if( node.values.length>0 ) {
615                int idx = node.values.length-1;
616                return new KeyValueEntry(node.keys[idx], node.values[idx]);
617            } else {
618                return null;
619            }
620        }
621        
622        public BTreeNode<Key,Value> getFirstLeafNode(Transaction tx) throws IOException {
623            BTreeNode<Key, Value> node = this;
624            while( node .isBranch() ) {
625                node = node.getChild(tx, 0);
626            }
627            return node;
628        }
629        
630        public Iterator<Map.Entry<Key,Value>> iterator(final Transaction tx, Key startKey) throws IOException {
631            if (startKey == null) {
632                return iterator(tx);
633            }
634            if( isBranch() ) {
635                return getLeafNode(tx, this, startKey).iterator(tx, startKey);
636            } else {
637                int idx = Arrays.binarySearch(keys, startKey);
638                if (idx < 0) {
639                    idx = -(idx + 1);
640                }
641                return new BTreeIterator(tx, this, idx);
642            }
643        }
644    
645        public Iterator<Map.Entry<Key,Value>> iterator(final Transaction tx) throws IOException {
646            return new BTreeIterator(tx, getFirstLeafNode(tx), 0);
647        }
648        
649        public void clear(Transaction tx) throws IOException {
650            if( isBranch() ) {
651                for (int i = 0; i < children.length; i++) {
652                    BTreeNode<Key, Value> node = index.loadNode(tx, children[i], this);
653                    node.clear(tx);
654                    tx.free(node.getPage());
655                }
656            }
657            // Reset the root node to be a leaf.
658            if( parent == null ) {
659                setLeafData(createKeyArray(0), createValueArray(0));
660                next=-1;
661                index.storeNode(tx, this, true);
662            }
663        }
664    
665    
666        private static <Key,Value> BTreeNode<Key, Value> getLeafNode(Transaction tx, final BTreeNode<Key, Value> node, Key key) throws IOException {
667            BTreeNode<Key, Value> current = node;
668            while( true ) {
669                if( current.isBranch() ) {
670                    int idx = Arrays.binarySearch(current.keys, key);
671                    idx = idx < 0 ? -(idx + 1) : idx + 1;
672                    BTreeNode<Key, Value> child = current.getChild(tx, idx);        
673    
674                    // A little cycle detection for sanity's sake
675                    if( child == node ) {
676                        throw new IOException("BTree corrupted: Cylce detected.");
677                    }
678                    
679                    current = child;
680                } else {
681                    break;
682                }
683            }
684            return current;
685        }
686    
687        public boolean contains(Transaction tx, Key key) throws IOException {
688            if (key == null) {
689                throw new IllegalArgumentException("Key cannot be null");
690            }
691    
692            if( isBranch() ) {
693                return getLeafNode(tx, this, key).contains(tx, key);
694            } else {
695                int idx = Arrays.binarySearch(keys, key);
696                if (idx < 0) {
697                    return false;
698                } else {
699                    return true;
700                }
701            }
702        }
703    
704        ///////////////////////////////////////////////////////////////////
705        // Implementation methods
706        ///////////////////////////////////////////////////////////////////
707     
708    
709        private boolean allowOverflow() {
710            // Only allow page overflow if there are <= 3 keys in the node.  Otherwise a split will occur on overflow
711            return this.keys.length<=3;
712        }
713    
714    
715        private void setLeafData(Key[] keys, Value[] values) {
716            this.keys = keys;
717            this.values = values;
718            this.children = null;
719        }
720        
721        private void setBranchData(Key[] keys, long[] nodeIds) {
722            this.keys = keys;
723            this.children = nodeIds;
724            this.values = null;
725        }
726    
727        @SuppressWarnings("unchecked")
728        private Key[] createKeyArray(int size) {
729            return (Key[])new Object[size];
730        }
731    
732        @SuppressWarnings("unchecked")
733        private Value[] createValueArray(int size) {
734            return (Value[])new Object[size];
735        }
736        
737        @SuppressWarnings("unchecked")
738        static private <T> T[] arrayDelete(T[] vals, int idx) {
739            T[] newVals = (T[])new Object[vals.length - 1];
740            if (idx > 0) {
741                System.arraycopy(vals, 0, newVals, 0, idx);
742            }
743            if (idx < newVals.length) {
744                System.arraycopy(vals, idx + 1, newVals, idx, newVals.length - idx);
745            }
746            return newVals;
747        }
748        
749        static private long[] arrayDelete(long[] vals, int idx) {
750            long[] newVals = new long[vals.length - 1];
751            if (idx > 0) {
752                System.arraycopy(vals, 0, newVals, 0, idx);
753            }
754            if (idx < newVals.length) {
755                System.arraycopy(vals, idx + 1, newVals, idx, newVals.length - idx);
756            }
757            return newVals;
758        }
759    
760        @SuppressWarnings("unchecked")
761        static private <T> T[] arrayInsert(T[] vals, T val, int idx) {
762            T[] newVals = (T[])new Object[vals.length + 1];
763            if (idx > 0) {
764                System.arraycopy(vals, 0, newVals, 0, idx);
765            }
766            newVals[idx] = val;
767            if (idx < vals.length) {
768                System.arraycopy(vals, idx, newVals, idx + 1, vals.length - idx);
769            }
770            return newVals;
771        }
772    
773    
774        static private long[] arrayInsert(long[] vals, long val, int idx) {
775            
776            long[] newVals = new long[vals.length + 1];
777            if (idx > 0) {
778                System.arraycopy(vals, 0, newVals, 0, idx);
779            }
780            newVals[idx] = val;
781            if (idx < vals.length) {
782                System.arraycopy(vals, idx, newVals, idx + 1, vals.length - idx);
783            }
784            return newVals;
785        }
786    
787        ///////////////////////////////////////////////////////////////////
788        // Property Accessors
789        ///////////////////////////////////////////////////////////////////
790        private boolean isBranch() {
791            return children!=null;
792        }
793    
794        public long getPageId() {
795            return page.getPageId();
796        }
797    
798        public BTreeNode<Key, Value> getParent() {
799            return parent;
800        }
801    
802        public void setParent(BTreeNode<Key, Value> parent) {
803            this.parent = parent;
804        }
805    
806        public Page<BTreeNode<Key, Value>> getPage() {
807            return page;
808        }
809    
810        public void setPage(Page<BTreeNode<Key, Value>> page) {
811            this.page = page;
812        }
813    
814        public long getNext() {
815            return next;
816        }
817    
818        public void setNext(long next) {
819            this.next = next;
820        }
821        
822        @Override
823        public String toString() {
824            return "[BTreeNode "+(isBranch()?"branch":"leaf")+": "+Arrays.asList(keys)+"]";
825        }
826    
827    }
828    
829