src/java/org/apache/cassandra/db/partitions/AtomicBTreePartition.java - cassandra - Git at Google

 /*
  * Licensed to the Apache Software Foundation (ASF) under one
  * or more contributor license agreements.  See the NOTICE file
  * distributed with this work for additional information
  * regarding copyright ownership.  The ASF licenses this file
  * to you under the Apache License, Version 2.0 (the
  * "License"); you may not use this file except in compliance
  * with the License.  You may obtain a copy of the License at
  *
  *     http://www.apache.org/licenses/LICENSE-2.0
  *
  * Unless required by applicable law or agreed to in writing, software
  * distributed under the License is distributed on an "AS IS" BASIS,
  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
 package org.apache.cassandra.db.partitions;

 import java.nio.ByteBuffer;
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
 import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
 import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;

 import org.apache.cassandra.config.CFMetaData;
 import org.apache.cassandra.config.DatabaseDescriptor;
 import org.apache.cassandra.db.*;
 import org.apache.cassandra.db.filter.ColumnFilter;
 import org.apache.cassandra.db.rows.*;
 import org.apache.cassandra.index.transactions.UpdateTransaction;
 import org.apache.cassandra.utils.FBUtilities;
 import org.apache.cassandra.utils.ObjectSizes;
 import org.apache.cassandra.utils.SearchIterator;
 import org.apache.cassandra.utils.btree.BTree;
 import org.apache.cassandra.utils.btree.UpdateFunction;
 import org.apache.cassandra.utils.concurrent.Locks;
 import org.apache.cassandra.utils.concurrent.OpOrder;
 import org.apache.cassandra.utils.memory.HeapAllocator;
 import org.apache.cassandra.utils.memory.MemtableAllocator;

 /**
  * A thread-safe and atomic Partition implementation.
  *
  * Operations (in particular addAll) on this implementation are atomic and
  * isolated (in the sense of ACID). Typically a addAll is guaranteed that no
  * other thread can see the state where only parts but not all rows have
  * been added.
  */
 public class AtomicBTreePartition extends AbstractBTreePartition
 {
     public static final long EMPTY_SIZE = ObjectSizes.measure(new AtomicBTreePartition(CFMetaData.createFake("keyspace", "table"),
                                                                                        DatabaseDescriptor.getPartitioner().decorateKey(ByteBuffer.allocate(1)),
                                                                                        null));

     // Reserved values for wasteTracker field. These values must not be consecutive (see avoidReservedValues)
     private static final int TRACKER_NEVER_WASTED = 0;
     private static final int TRACKER_PESSIMISTIC_LOCKING = Integer.MAX_VALUE;

     // The granularity with which we track wasted allocation/work; we round up
     private static final int ALLOCATION_GRANULARITY_BYTES = 1024;
     // The number of bytes we have to waste in excess of our acceptable realtime rate of waste (defined below)
     private static final long EXCESS_WASTE_BYTES = 10 * 1024 * 1024L;
     private static final int EXCESS_WASTE_OFFSET = (int) (EXCESS_WASTE_BYTES / ALLOCATION_GRANULARITY_BYTES);
     // Note this is a shift, because dividing a long time and then picking the low 32 bits doesn't give correct rollover behavior
     private static final int CLOCK_SHIFT = 17;
     // CLOCK_GRANULARITY = 1^9ns >> CLOCK_SHIFT == 132us == (1/7.63)ms

     private static final AtomicIntegerFieldUpdater<AtomicBTreePartition> wasteTrackerUpdater = AtomicIntegerFieldUpdater.newUpdater(AtomicBTreePartition.class, "wasteTracker");
     private static final AtomicReferenceFieldUpdater<AtomicBTreePartition, Holder> refUpdater = AtomicReferenceFieldUpdater.newUpdater(AtomicBTreePartition.class, Holder.class, "ref");

     /**
      * (clock + allocation) granularity are combined to give us an acceptable (waste) allocation rate that is defined by
      * the passage of real time of ALLOCATION_GRANULARITY_BYTES/CLOCK_GRANULARITY, or in this case 7.63Kb/ms, or 7.45Mb/s
      *
      * in wasteTracker we maintain within EXCESS_WASTE_OFFSET before the current time; whenever we waste bytes
      * we increment the current value if it is within this window, and set it to the min of the window plus our waste
      * otherwise.
      */
     private volatile int wasteTracker = TRACKER_NEVER_WASTED;

     private final MemtableAllocator allocator;
     private volatile Holder ref;

     public AtomicBTreePartition(CFMetaData metadata, DecoratedKey partitionKey, MemtableAllocator allocator)
     {
         // involved in potential bug? partition columns may be a subset if we alter columns while it's in memtable
         super(metadata, partitionKey);
         this.allocator = allocator;
         this.ref = EMPTY;
     }

     protected Holder holder()
     {
         return ref;
     }

     protected boolean canHaveShadowedData()
     {
         return true;
     }

     /**
      * Adds a given update to this in-memtable partition.
      *
      * @return an array containing first the difference in size seen after merging the updates, and second the minimum
      * time detla between updates.
      */
     public long[] addAllWithSizeDelta(final PartitionUpdate update, OpOrder.Group writeOp, UpdateTransaction indexer)
     {
         RowUpdater updater = new RowUpdater(this, allocator, writeOp, indexer);
         DeletionInfo inputDeletionInfoCopy = null;
         boolean monitorOwned = false;
         try
         {
             monitorOwned = maybeLock(writeOp);
             indexer.start();

             while (true)
             {
                 Holder current = ref;
                 updater.ref = current;
                 updater.reset();

                 if (!update.deletionInfo().getPartitionDeletion().isLive())
                     indexer.onPartitionDeletion(update.deletionInfo().getPartitionDeletion());

                 if (update.deletionInfo().hasRanges())
                     update.deletionInfo().rangeIterator(false).forEachRemaining(indexer::onRangeTombstone);

                 DeletionInfo deletionInfo;
                 if (update.deletionInfo().mayModify(current.deletionInfo))
                 {
                     if (inputDeletionInfoCopy == null)
                         inputDeletionInfoCopy = update.deletionInfo().copy(HeapAllocator.instance);

                     deletionInfo = current.deletionInfo.mutableCopy().add(inputDeletionInfoCopy);
                     updater.allocated(deletionInfo.unsharedHeapSize() - current.deletionInfo.unsharedHeapSize());
                 }
                 else
                 {
                     deletionInfo = current.deletionInfo;
                 }

                 PartitionColumns columns = update.columns().mergeTo(current.columns);
                 Row newStatic = update.staticRow();
                 Row staticRow = newStatic.isEmpty()
                               ? current.staticRow
                               : (current.staticRow.isEmpty() ? updater.apply(newStatic) : updater.apply(current.staticRow, newStatic));
                 Object[] tree = BTree.update(current.tree, update.metadata().comparator, update, update.rowCount(), updater);
                 EncodingStats newStats = current.stats.mergeWith(update.stats());

                 if (tree != null && refUpdater.compareAndSet(this, current, new Holder(columns, tree, deletionInfo, staticRow, newStats)))
                 {
                     updater.finish();
                     return new long[]{ updater.dataSize, updater.colUpdateTimeDelta };
                 }
                 else if (!monitorOwned)
                 {
                     monitorOwned = maybeLock(updater.heapSize, writeOp);
                 }
             }
         }
         finally
         {
             indexer.commit();
             if (monitorOwned)
                 Locks.monitorExitUnsafe(this);
         }
     }

     @Override
     public DeletionInfo deletionInfo()
     {
         return allocator.ensureOnHeap().applyToDeletionInfo(super.deletionInfo());
     }

     @Override
     public Row staticRow()
     {
         return allocator.ensureOnHeap().applyToStatic(super.staticRow());
     }

     @Override
     public DecoratedKey partitionKey()
     {
         return allocator.ensureOnHeap().applyToPartitionKey(super.partitionKey());
     }

     @Override
     public Row getRow(Clustering clustering)
     {
         return allocator.ensureOnHeap().applyToRow(super.getRow(clustering));
     }

     @Override
     public Row lastRow()
     {
         return allocator.ensureOnHeap().applyToRow(super.lastRow());
     }

     @Override
     public SearchIterator<Clustering, Row> searchIterator(ColumnFilter columns, boolean reversed)
     {
         return allocator.ensureOnHeap().applyToPartition(super.searchIterator(columns, reversed));
     }

     @Override
     public UnfilteredRowIterator unfilteredIterator(ColumnFilter selection, Slices slices, boolean reversed)
     {
         return allocator.ensureOnHeap().applyToPartition(super.unfilteredIterator(selection, slices, reversed));
     }

     @Override
     public UnfilteredRowIterator unfilteredIterator()
     {
         return allocator.ensureOnHeap().applyToPartition(super.unfilteredIterator());
     }

     @Override
     public UnfilteredRowIterator unfilteredIterator(Holder current, ColumnFilter selection, Slices slices, boolean reversed)
     {
         return allocator.ensureOnHeap().applyToPartition(super.unfilteredIterator(current, selection, slices, reversed));
     }

     @Override
     public Iterator<Row> iterator()
     {
         return allocator.ensureOnHeap().applyToPartition(super.iterator());
     }

     private boolean maybeLock(OpOrder.Group writeOp)
     {
         if (!useLock())
             return false;

         return lockIfOldest(writeOp);
     }

     private boolean maybeLock(long addWaste, OpOrder.Group writeOp)
     {
         if (!updateWastedAllocationTracker(addWaste))
             return false;

         return lockIfOldest(writeOp);
     }

     private boolean lockIfOldest(OpOrder.Group writeOp)
     {
         if (!writeOp.isOldestLiveGroup())
         {
             Thread.yield();
             if (!writeOp.isOldestLiveGroup())
                 return false;
         }

         Locks.monitorEnterUnsafe(this);
         return true;
     }

     public boolean useLock()
     {
         return wasteTracker == TRACKER_PESSIMISTIC_LOCKING;
     }

     /**
      * Update the wasted allocation tracker state based on newly wasted allocation information
      *
      * @param wastedBytes the number of bytes wasted by this thread
      * @return true if the caller should now proceed with pessimistic locking because the waste limit has been reached
      */
     private boolean updateWastedAllocationTracker(long wastedBytes)
     {
         // Early check for huge allocation that exceeds the limit
         if (wastedBytes < EXCESS_WASTE_BYTES)
         {
             // We round up to ensure work < granularity are still accounted for
             int wastedAllocation = ((int) (wastedBytes + ALLOCATION_GRANULARITY_BYTES - 1)) / ALLOCATION_GRANULARITY_BYTES;

             int oldTrackerValue;
             while (TRACKER_PESSIMISTIC_LOCKING != (oldTrackerValue = wasteTracker))
             {
                 // Note this time value has an arbitrary offset, but is a constant rate 32 bit counter (that may wrap)
                 int time = (int) (System.nanoTime() >>> CLOCK_SHIFT);
                 int delta = oldTrackerValue - time;
                 if (oldTrackerValue == TRACKER_NEVER_WASTED || delta >= 0 || delta < -EXCESS_WASTE_OFFSET)
                     delta = -EXCESS_WASTE_OFFSET;
                 delta += wastedAllocation;
                 if (delta >= 0)
                     break;
                 if (wasteTrackerUpdater.compareAndSet(this, oldTrackerValue, avoidReservedValues(time + delta)))
                     return false;
             }
         }
         // We have definitely reached our waste limit so set the state if it isn't already
         wasteTrackerUpdater.set(this, TRACKER_PESSIMISTIC_LOCKING);
         // And tell the caller to proceed with pessimistic locking
         return true;
     }

     private static int avoidReservedValues(int wasteTracker)
     {
         if (wasteTracker == TRACKER_NEVER_WASTED || wasteTracker == TRACKER_PESSIMISTIC_LOCKING)
             return wasteTracker + 1;
         return wasteTracker;
     }

     // the function we provide to the btree utilities to perform any column replacements
     private static final class RowUpdater implements UpdateFunction<Row, Row>
     {
         final AtomicBTreePartition updating;
         final MemtableAllocator allocator;
         final OpOrder.Group writeOp;
         final UpdateTransaction indexer;
         final int nowInSec;
         Holder ref;
         Row.Builder regularBuilder;
         long dataSize;
         long heapSize;
         long colUpdateTimeDelta = Long.MAX_VALUE;
         List<Row> inserted; // TODO: replace with walk of aborted BTree

         private RowUpdater(AtomicBTreePartition updating, MemtableAllocator allocator, OpOrder.Group writeOp, UpdateTransaction indexer)
         {
             this.updating = updating;
             this.allocator = allocator;
             this.writeOp = writeOp;
             this.indexer = indexer;
             this.nowInSec = FBUtilities.nowInSeconds();
         }

         private Row.Builder builder(Clustering clustering)
         {
             boolean isStatic = clustering == Clustering.STATIC_CLUSTERING;
             // We know we only insert/update one static per PartitionUpdate, so no point in saving the builder
             if (isStatic)
                 return allocator.rowBuilder(writeOp);

             if (regularBuilder == null)
                 regularBuilder = allocator.rowBuilder(writeOp);
             return regularBuilder;
         }

         public Row apply(Row insert)
         {
             Row data = Rows.copy(insert, builder(insert.clustering())).build();
             indexer.onInserted(insert);

             this.dataSize += data.dataSize();
             this.heapSize += data.unsharedHeapSizeExcludingData();
             if (inserted == null)
                 inserted = new ArrayList<>();
             inserted.add(data);
             return data;
         }

         public Row apply(Row existing, Row update)
         {
             Row.Builder builder = builder(existing.clustering());
             colUpdateTimeDelta = Math.min(colUpdateTimeDelta, Rows.merge(existing, update, builder, nowInSec));

             Row reconciled = builder.build();

             indexer.onUpdated(existing, reconciled);

             dataSize += reconciled.dataSize() - existing.dataSize();
             heapSize += reconciled.unsharedHeapSizeExcludingData() - existing.unsharedHeapSizeExcludingData();
             if (inserted == null)
                 inserted = new ArrayList<>();
             inserted.add(reconciled);

             return reconciled;
         }

         protected void reset()
         {
             this.dataSize = 0;
             this.heapSize = 0;
             if (inserted != null)
                 inserted.clear();
         }
         public boolean abortEarly()
         {
             return updating.ref != ref;
         }

         public void allocated(long heapSize)
         {
             this.heapSize += heapSize;
         }

         protected void finish()
         {
             allocator.onHeap().adjust(heapSize, writeOp);
         }
     }
 }
	/*
	* Licensed to the Apache Software Foundation (ASF) under one
	* or more contributor license agreements. See the NOTICE file
	* distributed with this work for additional information
	* regarding copyright ownership. The ASF licenses this file
	* to you under the Apache License, Version 2.0 (the
	* "License"); you may not use this file except in compliance
	* with the License. You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
	*
	* Unless required by applicable law or agreed to in writing, software
	* distributed under the License is distributed on an "AS IS" BASIS,
	* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	* See the License for the specific language governing permissions and
	* limitations under the License.
	*/
	package org.apache.cassandra.db.partitions;

	import java.nio.ByteBuffer;
	import java.util.ArrayList;
	import java.util.Iterator;
	import java.util.List;
	import java.util.concurrent.atomic.AtomicIntegerFieldUpdater;
	import java.util.concurrent.atomic.AtomicReferenceFieldUpdater;

	import org.apache.cassandra.config.CFMetaData;
	import org.apache.cassandra.config.DatabaseDescriptor;
	import org.apache.cassandra.db.*;
	import org.apache.cassandra.db.filter.ColumnFilter;
	import org.apache.cassandra.db.rows.*;
	import org.apache.cassandra.index.transactions.UpdateTransaction;
	import org.apache.cassandra.utils.FBUtilities;
	import org.apache.cassandra.utils.ObjectSizes;
	import org.apache.cassandra.utils.SearchIterator;
	import org.apache.cassandra.utils.btree.BTree;
	import org.apache.cassandra.utils.btree.UpdateFunction;
	import org.apache.cassandra.utils.concurrent.Locks;
	import org.apache.cassandra.utils.concurrent.OpOrder;
	import org.apache.cassandra.utils.memory.HeapAllocator;
	import org.apache.cassandra.utils.memory.MemtableAllocator;

	/**
	* A thread-safe and atomic Partition implementation.
	*
	* Operations (in particular addAll) on this implementation are atomic and
	* isolated (in the sense of ACID). Typically a addAll is guaranteed that no
	* other thread can see the state where only parts but not all rows have
	* been added.
	*/
	public class AtomicBTreePartition extends AbstractBTreePartition
	{
	public static final long EMPTY_SIZE = ObjectSizes.measure(new AtomicBTreePartition(CFMetaData.createFake("keyspace", "table"),
	DatabaseDescriptor.getPartitioner().decorateKey(ByteBuffer.allocate(1)),
	null));

	// Reserved values for wasteTracker field. These values must not be consecutive (see avoidReservedValues)
	private static final int TRACKER_NEVER_WASTED = 0;
	private static final int TRACKER_PESSIMISTIC_LOCKING = Integer.MAX_VALUE;

	// The granularity with which we track wasted allocation/work; we round up
	private static final int ALLOCATION_GRANULARITY_BYTES = 1024;
	// The number of bytes we have to waste in excess of our acceptable realtime rate of waste (defined below)
	private static final long EXCESS_WASTE_BYTES = 10 * 1024 * 1024L;
	private static final int EXCESS_WASTE_OFFSET = (int) (EXCESS_WASTE_BYTES / ALLOCATION_GRANULARITY_BYTES);
	// Note this is a shift, because dividing a long time and then picking the low 32 bits doesn't give correct rollover behavior
	private static final int CLOCK_SHIFT = 17;
	// CLOCK_GRANULARITY = 1^9ns >> CLOCK_SHIFT == 132us == (1/7.63)ms

	private static final AtomicIntegerFieldUpdater<AtomicBTreePartition> wasteTrackerUpdater = AtomicIntegerFieldUpdater.newUpdater(AtomicBTreePartition.class, "wasteTracker");
	private static final AtomicReferenceFieldUpdater<AtomicBTreePartition, Holder> refUpdater = AtomicReferenceFieldUpdater.newUpdater(AtomicBTreePartition.class, Holder.class, "ref");

	/**
	* (clock + allocation) granularity are combined to give us an acceptable (waste) allocation rate that is defined by
	* the passage of real time of ALLOCATION_GRANULARITY_BYTES/CLOCK_GRANULARITY, or in this case 7.63Kb/ms, or 7.45Mb/s
	*
	* in wasteTracker we maintain within EXCESS_WASTE_OFFSET before the current time; whenever we waste bytes
	* we increment the current value if it is within this window, and set it to the min of the window plus our waste
	* otherwise.
	*/
	private volatile int wasteTracker = TRACKER_NEVER_WASTED;

	private final MemtableAllocator allocator;
	private volatile Holder ref;

	public AtomicBTreePartition(CFMetaData metadata, DecoratedKey partitionKey, MemtableAllocator allocator)
	{
	// involved in potential bug? partition columns may be a subset if we alter columns while it's in memtable
	super(metadata, partitionKey);
	this.allocator = allocator;
	this.ref = EMPTY;
	}

	protected Holder holder()
	{
	return ref;
	}

	protected boolean canHaveShadowedData()
	{
	return true;
	}

	/**
	* Adds a given update to this in-memtable partition.
	*
	* @return an array containing first the difference in size seen after merging the updates, and second the minimum
	* time detla between updates.
	*/
	public long[] addAllWithSizeDelta(final PartitionUpdate update, OpOrder.Group writeOp, UpdateTransaction indexer)
	{
	RowUpdater updater = new RowUpdater(this, allocator, writeOp, indexer);
	DeletionInfo inputDeletionInfoCopy = null;
	boolean monitorOwned = false;
	try
	{
	monitorOwned = maybeLock(writeOp);
	indexer.start();

	while (true)
	{
	Holder current = ref;
	updater.ref = current;
	updater.reset();

	if (!update.deletionInfo().getPartitionDeletion().isLive())
	indexer.onPartitionDeletion(update.deletionInfo().getPartitionDeletion());

	if (update.deletionInfo().hasRanges())
	update.deletionInfo().rangeIterator(false).forEachRemaining(indexer::onRangeTombstone);

	DeletionInfo deletionInfo;
	if (update.deletionInfo().mayModify(current.deletionInfo))
	{
	if (inputDeletionInfoCopy == null)
	inputDeletionInfoCopy = update.deletionInfo().copy(HeapAllocator.instance);

	deletionInfo = current.deletionInfo.mutableCopy().add(inputDeletionInfoCopy);
	updater.allocated(deletionInfo.unsharedHeapSize() - current.deletionInfo.unsharedHeapSize());
	}
	else
	{
	deletionInfo = current.deletionInfo;
	}

	PartitionColumns columns = update.columns().mergeTo(current.columns);
	Row newStatic = update.staticRow();
	Row staticRow = newStatic.isEmpty()
	? current.staticRow
	: (current.staticRow.isEmpty() ? updater.apply(newStatic) : updater.apply(current.staticRow, newStatic));
	Object[] tree = BTree.update(current.tree, update.metadata().comparator, update, update.rowCount(), updater);
	EncodingStats newStats = current.stats.mergeWith(update.stats());

	if (tree != null && refUpdater.compareAndSet(this, current, new Holder(columns, tree, deletionInfo, staticRow, newStats)))
	{
	updater.finish();
	return new long[]{ updater.dataSize, updater.colUpdateTimeDelta };
	}
	else if (!monitorOwned)
	{
	monitorOwned = maybeLock(updater.heapSize, writeOp);
	}
	}
	}
	finally
	{
	indexer.commit();
	if (monitorOwned)
	Locks.monitorExitUnsafe(this);
	}
	}

	@Override
	public DeletionInfo deletionInfo()
	{
	return allocator.ensureOnHeap().applyToDeletionInfo(super.deletionInfo());
	}

	@Override
	public Row staticRow()
	{
	return allocator.ensureOnHeap().applyToStatic(super.staticRow());
	}

	@Override
	public DecoratedKey partitionKey()
	{
	return allocator.ensureOnHeap().applyToPartitionKey(super.partitionKey());
	}

	@Override
	public Row getRow(Clustering clustering)
	{
	return allocator.ensureOnHeap().applyToRow(super.getRow(clustering));
	}

	@Override
	public Row lastRow()
	{
	return allocator.ensureOnHeap().applyToRow(super.lastRow());
	}

	@Override
	public SearchIterator<Clustering, Row> searchIterator(ColumnFilter columns, boolean reversed)
	{
	return allocator.ensureOnHeap().applyToPartition(super.searchIterator(columns, reversed));
	}

	@Override
	public UnfilteredRowIterator unfilteredIterator(ColumnFilter selection, Slices slices, boolean reversed)
	{
	return allocator.ensureOnHeap().applyToPartition(super.unfilteredIterator(selection, slices, reversed));
	}

	@Override
	public UnfilteredRowIterator unfilteredIterator()
	{
	return allocator.ensureOnHeap().applyToPartition(super.unfilteredIterator());
	}

	@Override
	public UnfilteredRowIterator unfilteredIterator(Holder current, ColumnFilter selection, Slices slices, boolean reversed)
	{
	return allocator.ensureOnHeap().applyToPartition(super.unfilteredIterator(current, selection, slices, reversed));
	}

	@Override
	public Iterator<Row> iterator()
	{
	return allocator.ensureOnHeap().applyToPartition(super.iterator());
	}

	private boolean maybeLock(OpOrder.Group writeOp)
	{
	if (!useLock())
	return false;

	return lockIfOldest(writeOp);
	}

	private boolean maybeLock(long addWaste, OpOrder.Group writeOp)
	{
	if (!updateWastedAllocationTracker(addWaste))
	return false;

	return lockIfOldest(writeOp);
	}

	private boolean lockIfOldest(OpOrder.Group writeOp)
	{
	if (!writeOp.isOldestLiveGroup())
	{
	Thread.yield();
	if (!writeOp.isOldestLiveGroup())
	return false;
	}

	Locks.monitorEnterUnsafe(this);
	return true;
	}

	public boolean useLock()
	{
	return wasteTracker == TRACKER_PESSIMISTIC_LOCKING;
	}

	/**
	* Update the wasted allocation tracker state based on newly wasted allocation information
	*
	* @param wastedBytes the number of bytes wasted by this thread
	* @return true if the caller should now proceed with pessimistic locking because the waste limit has been reached
	*/
	private boolean updateWastedAllocationTracker(long wastedBytes)
	{
	// Early check for huge allocation that exceeds the limit
	if (wastedBytes < EXCESS_WASTE_BYTES)
	{
	// We round up to ensure work < granularity are still accounted for
	int wastedAllocation = ((int) (wastedBytes + ALLOCATION_GRANULARITY_BYTES - 1)) / ALLOCATION_GRANULARITY_BYTES;

	int oldTrackerValue;
	while (TRACKER_PESSIMISTIC_LOCKING != (oldTrackerValue = wasteTracker))
	{
	// Note this time value has an arbitrary offset, but is a constant rate 32 bit counter (that may wrap)
	int time = (int) (System.nanoTime() >>> CLOCK_SHIFT);
	int delta = oldTrackerValue - time;
	if (oldTrackerValue == TRACKER_NEVER_WASTED \|\| delta >= 0 \|\| delta < -EXCESS_WASTE_OFFSET)
	delta = -EXCESS_WASTE_OFFSET;
	delta += wastedAllocation;
	if (delta >= 0)
	break;
	if (wasteTrackerUpdater.compareAndSet(this, oldTrackerValue, avoidReservedValues(time + delta)))
	return false;
	}
	}
	// We have definitely reached our waste limit so set the state if it isn't already
	wasteTrackerUpdater.set(this, TRACKER_PESSIMISTIC_LOCKING);
	// And tell the caller to proceed with pessimistic locking
	return true;
	}

	private static int avoidReservedValues(int wasteTracker)
	{
	if (wasteTracker == TRACKER_NEVER_WASTED \|\| wasteTracker == TRACKER_PESSIMISTIC_LOCKING)
	return wasteTracker + 1;
	return wasteTracker;
	}

	// the function we provide to the btree utilities to perform any column replacements
	private static final class RowUpdater implements UpdateFunction<Row, Row>
	{
	final AtomicBTreePartition updating;
	final MemtableAllocator allocator;
	final OpOrder.Group writeOp;
	final UpdateTransaction indexer;
	final int nowInSec;
	Holder ref;
	Row.Builder regularBuilder;
	long dataSize;
	long heapSize;
	long colUpdateTimeDelta = Long.MAX_VALUE;
	List<Row> inserted; // TODO: replace with walk of aborted BTree

	private RowUpdater(AtomicBTreePartition updating, MemtableAllocator allocator, OpOrder.Group writeOp, UpdateTransaction indexer)
	{
	this.updating = updating;
	this.allocator = allocator;
	this.writeOp = writeOp;
	this.indexer = indexer;
	this.nowInSec = FBUtilities.nowInSeconds();
	}

	private Row.Builder builder(Clustering clustering)
	{
	boolean isStatic = clustering == Clustering.STATIC_CLUSTERING;
	// We know we only insert/update one static per PartitionUpdate, so no point in saving the builder
	if (isStatic)
	return allocator.rowBuilder(writeOp);

	if (regularBuilder == null)
	regularBuilder = allocator.rowBuilder(writeOp);
	return regularBuilder;
	}

	public Row apply(Row insert)
	{
	Row data = Rows.copy(insert, builder(insert.clustering())).build();
	indexer.onInserted(insert);

	this.dataSize += data.dataSize();
	this.heapSize += data.unsharedHeapSizeExcludingData();
	if (inserted == null)
	inserted = new ArrayList<>();
	inserted.add(data);
	return data;
	}

	public Row apply(Row existing, Row update)
	{
	Row.Builder builder = builder(existing.clustering());
	colUpdateTimeDelta = Math.min(colUpdateTimeDelta, Rows.merge(existing, update, builder, nowInSec));

	Row reconciled = builder.build();

	indexer.onUpdated(existing, reconciled);

	dataSize += reconciled.dataSize() - existing.dataSize();
	heapSize += reconciled.unsharedHeapSizeExcludingData() - existing.unsharedHeapSizeExcludingData();
	if (inserted == null)
	inserted = new ArrayList<>();
	inserted.add(reconciled);

	return reconciled;
	}

	protected void reset()
	{
	this.dataSize = 0;
	this.heapSize = 0;
	if (inserted != null)
	inserted.clear();
	}
	public boolean abortEarly()
	{
	return updating.ref != ref;
	}

	public void allocated(long heapSize)
	{
	this.heapSize += heapSize;
	}

	protected void finish()
	{
	allocator.onHeap().adjust(heapSize, writeOp);
	}
	}
	}