HBASE-14063 Use BufferBackedCell in read path after HBASE-12213 and

HBASE-12295 (ram)

hbase-common/src/main/java/org/apache/hadoop/hbase/ByteBufferedKeyOnlyKeyValue.java

@@ -1,5 +1,4 @@
 /**
- * Copyright The Apache Software Foundation
  *
  * Licensed to the Apache Software Foundation (ASF) under one
  * or more contributor license agreements.  See the NOTICE file
@@ -27,19 +26,37 @@ import org.apache.hadoop.hbase.util.Bytes;
 
 /**
  * This is a key only Cell implementation which is identical to {@link KeyValue.KeyOnlyKeyValue}
- * with respect to key serialization but have its data in off heap memory.
+ * with respect to key serialization but have its data in the form of Byte buffer
+ * (onheap and offheap).
  */
 @InterfaceAudience.Private
-public class OffheapKeyOnlyKeyValue extends ByteBufferedCell {
+public class ByteBufferedKeyOnlyKeyValue extends ByteBufferedCell {
 
   private ByteBuffer buf;
   private int offset = 0; // offset into buffer where key starts at
   private int length = 0; // length of this.
   private short rowLen;
 
-  public OffheapKeyOnlyKeyValue(ByteBuffer buf, int offset, int length) {
-    assert buf.isDirect();
-    this.buf = buf;
+  /**
+   * Used in cases where we want to avoid lot of garbage by allocating new objects with different
+   * keys. Use the emtpy construtor and set the keys using {@link #setKey(ByteBuffer, int, int)}
+   */
+  public ByteBufferedKeyOnlyKeyValue() {
+  }
+
+  public ByteBufferedKeyOnlyKeyValue(ByteBuffer buf, int offset, int length) {
+    setKey(buf, offset, length);
+  }
+
+  /**
+   * A setter that helps to avoid object creation every time and whenever
+   * there is a need to create new OffheapKeyOnlyKeyValue.
+   * @param key
+   * @param offset
+   * @param length
+   */
+  public void setKey(ByteBuffer key, int offset, int length) {
+    this.buf = key;
     this.offset = offset;
     this.length = length;
     this.rowLen = ByteBufferUtils.toShort(this.buf, this.offset);
@@ -47,11 +64,17 @@ public class OffheapKeyOnlyKeyValue extends ByteBufferedCell {
 
   @Override
   public byte[] getRowArray() {
+    if (this.buf.hasArray()) {
+      return this.buf.array();
+    }
     return CellUtil.cloneRow(this);
   }
 
   @Override
   public int getRowOffset() {
+    if (this.buf.hasArray()) {
+      return getRowPositionInByteBuffer() + this.buf.arrayOffset();
+    }
     return 0;
   }
 
@@ -62,11 +85,17 @@ public class OffheapKeyOnlyKeyValue extends ByteBufferedCell {
 
   @Override
   public byte[] getFamilyArray() {
+    if (this.buf.hasArray()) {
+      return this.buf.array();
+    }
     return CellUtil.cloneFamily(this);
   }
 
   @Override
   public int getFamilyOffset() {
+    if (this.buf.hasArray()) {
+      return getFamilyPositionInByteBuffer() + this.buf.arrayOffset();
+    }
     return 0;
   }
 
@@ -81,11 +110,17 @@ public class OffheapKeyOnlyKeyValue extends ByteBufferedCell {
 
   @Override
   public byte[] getQualifierArray() {
+    if (this.buf.hasArray()) {
+      return this.buf.array();
+    }
     return CellUtil.cloneQualifier(this);
   }
 
   @Override
   public int getQualifierOffset() {
+    if (this.buf.hasArray()) {
+      return getQualifierPositionInByteBuffer() + this.buf.arrayOffset();
+    }
     return 0;
   }
 

hbase-common/src/main/java/org/apache/hadoop/hbase/KeyValue.java

@@ -37,9 +37,8 @@ import java.util.Map;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.apache.hadoop.hbase.classification.InterfaceAudience;
-import org.apache.hadoop.hbase.io.ByteBufferOutputStream;
 import org.apache.hadoop.hbase.io.HeapSize;
-import org.apache.hadoop.hbase.io.util.StreamUtils;
+import org.apache.hadoop.hbase.util.ByteBufferUtils;
 import org.apache.hadoop.hbase.util.Bytes;
 import org.apache.hadoop.hbase.util.ClassSize;
 import org.apache.hadoop.io.IOUtils;
@@ -2475,22 +2474,11 @@ public class KeyValue implements Cell, HeapSize, Cloneable, SettableSequenceId,
     if (!withTags) {
       length = this.getKeyLength() + this.getValueLength() + KEYVALUE_INFRASTRUCTURE_SIZE;
     }
-    writeInt(out, length);
+    ByteBufferUtils.putInt(out, length);
     out.write(this.bytes, this.offset, length);
     return length + Bytes.SIZEOF_INT;
   }
 
-  // This does same as DataOuput#writeInt (big-endian, etc.)
-  public static void writeInt(OutputStream out, int v) throws IOException {
-    // We have writeInt in ByteBufferOutputStream so that it can directly write int to underlying
-    // ByteBuffer in one step.
-    if (out instanceof ByteBufferOutputStream) {
-      ((ByteBufferOutputStream) out).writeInt(v);
-    } else {
-      StreamUtils.writeInt(out, v);
-    }
-  }
-
   /**
    * Comparator that compares row component only of a KeyValue.
    */

hbase-common/src/main/java/org/apache/hadoop/hbase/KeyValueUtil.java

@@ -589,11 +589,11 @@ public class KeyValueUtil {
       int tlen = cell.getTagsLength();
 
       // write total length
-      KeyValue.writeInt(out, length(rlen, flen, qlen, vlen, tlen, withTags));
+      ByteBufferUtils.putInt(out, length(rlen, flen, qlen, vlen, tlen, withTags));
       // write key length
-      KeyValue.writeInt(out, keyLength(rlen, flen, qlen));
+      ByteBufferUtils.putInt(out, keyLength(rlen, flen, qlen));
       // write value length
-      KeyValue.writeInt(out, vlen);
+      ByteBufferUtils.putInt(out, vlen);
       // Write rowkey - 2 bytes rk length followed by rowkey bytes
       StreamUtils.writeShort(out, rlen);
       out.write(cell.getRowArray(), cell.getRowOffset(), rlen);

hbase-common/src/main/java/org/apache/hadoop/hbase/NoTagsKeyValue.java

@@ -23,6 +23,7 @@ import java.io.IOException;
 import java.io.OutputStream;
 
 import org.apache.hadoop.hbase.classification.InterfaceAudience;
+import org.apache.hadoop.hbase.util.ByteBufferUtils;
 import org.apache.hadoop.hbase.util.Bytes;
 
 /**
@@ -43,7 +44,7 @@ public class NoTagsKeyValue extends KeyValue {
   public int write(OutputStream out, boolean withTags) throws IOException {
     // In KeyValueUtil#oswrite we do a Cell serialization as KeyValue. Any changes doing here, pls
     // check KeyValueUtil#oswrite also and do necessary changes.
-    writeInt(out, this.length);
+    ByteBufferUtils.putInt(out, this.length);
     out.write(this.bytes, this.offset, this.length);
     return this.length + Bytes.SIZEOF_INT;
   }

hbase-common/src/main/java/org/apache/hadoop/hbase/OffheapKeyValue.java

@@ -0,0 +1,264 @@
+/**
+ * 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.hadoop.hbase;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import java.nio.ByteBuffer;
+
+import org.apache.hadoop.hbase.classification.InterfaceAudience;
+import org.apache.hadoop.hbase.io.HeapSize;
+import org.apache.hadoop.hbase.util.ByteBufferUtils;
+import org.apache.hadoop.hbase.util.Bytes;
+import org.apache.hadoop.hbase.util.ClassSize;
+
+/**
+ * This Cell is an implementation of {@link ByteBufferedCell} where the data resides in off heap
+ * memory.
+ */
+@InterfaceAudience.Private
+public class OffheapKeyValue extends ByteBufferedCell implements HeapSize, Cloneable,
+    SettableSequenceId, Streamable {
+
+  protected final ByteBuffer buf;
+  protected final int offset;
+  protected final int length;
+  private final short rowLen;
+  private final int keyLen;
+  private long seqId = 0;
+  private final boolean hasTags;
+  // TODO : See if famLen can be cached or not?
+
+  private static final int FIXED_HEAP_SIZE_OVERHEAD = ClassSize.OBJECT + ClassSize.REFERENCE
+      + ClassSize.align(ClassSize.BYTE_BUFFER) + (3 * Bytes.SIZEOF_INT) + Bytes.SIZEOF_SHORT
+      + Bytes.SIZEOF_BOOLEAN + Bytes.SIZEOF_LONG;
+
+  public OffheapKeyValue(ByteBuffer buf, int offset, int length, boolean hasTags) {
+    assert buf.isDirect();
+    this.buf = buf;
+    this.offset = offset;
+    this.length = length;
+    rowLen = ByteBufferUtils.toShort(this.buf, this.offset + KeyValue.ROW_OFFSET);
+    keyLen = ByteBufferUtils.toInt(this.buf, this.offset);
+    this.hasTags = hasTags;
+  }
+
+  @Override
+  public byte[] getRowArray() {
+    return CellUtil.cloneRow(this);
+  }
+
+  @Override
+  public int getRowOffset() {
+    return 0;
+  }
+
+  @Override
+  public short getRowLength() {
+    return this.rowLen;
+  }
+
+  @Override
+  public byte[] getFamilyArray() {
+    return CellUtil.cloneFamily(this);
+  }
+
+  @Override
+  public int getFamilyOffset() {
+    return 0;
+  }
+
+  @Override
+  public byte getFamilyLength() {
+    return getFamilyLength(getFamilyLengthPosition());
+  }
+
+  private int getFamilyLengthPosition() {
+    return this.offset + KeyValue.ROW_KEY_OFFSET + rowLen;
+  }
+
+  private byte getFamilyLength(int famLenPos) {
+    return ByteBufferUtils.toByte(this.buf, famLenPos);
+  }
+
+  @Override
+  public byte[] getQualifierArray() {
+    return CellUtil.cloneQualifier(this);
+  }
+
+  @Override
+  public int getQualifierOffset() {
+    return 0;
+  }
+
+  @Override
+  public int getQualifierLength() {
+    return getQualifierLength(getRowLength(), getFamilyLength());
+  }
+
+  private int getQualifierLength(int rlength, int flength) {
+    return this.keyLen - (int) KeyValue.getKeyDataStructureSize(rlength, flength, 0);
+  }
+
+  @Override
+  public long getTimestamp() {
+    int offset = getTimestampOffset(this.keyLen);
+    return ByteBufferUtils.toLong(this.buf, offset);
+  }
+
+  private int getTimestampOffset(int keyLen) {
+    return this.offset + KeyValue.ROW_OFFSET + keyLen - KeyValue.TIMESTAMP_TYPE_SIZE;
+  }
+
+  @Override
+  public byte getTypeByte() {
+    return ByteBufferUtils.toByte(this.buf, this.offset + this.keyLen - 1 + KeyValue.ROW_OFFSET);
+  }
+
+  @Override
+  public long getSequenceId() {
+    return this.seqId;
+  }
+
+  public void setSequenceId(long seqId) {
+    this.seqId = seqId;
+  }
+
+  @Override
+  public byte[] getValueArray() {
+    return CellUtil.cloneValue(this);
+  }
+
+  @Override
+  public int getValueOffset() {
+    return 0;
+  }
+
+  @Override
+  public int getValueLength() {
+    return ByteBufferUtils.toInt(this.buf, this.offset + Bytes.SIZEOF_INT);
+  }
+
+  @Override
+  public byte[] getTagsArray() {
+    return CellUtil.cloneTags(this);
+  }
+
+  @Override
+  public int getTagsOffset() {
+    return 0;
+  }
+
+  @Override
+  public int getTagsLength() {
+    if(!hasTags) {
+      return 0;
+    }
+    int tagsLen = this.length
+        - (this.keyLen + getValueLength() + KeyValue.KEYVALUE_INFRASTRUCTURE_SIZE);
+    if (tagsLen > 0) {
+      // There are some Tag bytes in the byte[]. So reduce 2 bytes which is
+      // added to denote the tags
+      // length
+      tagsLen -= KeyValue.TAGS_LENGTH_SIZE;
+    }
+    return tagsLen;
+  }
+
+  @Override
+  public ByteBuffer getRowByteBuffer() {
+    return this.buf;
+  }
+
+  @Override
+  public int getRowPositionInByteBuffer() {
+    return this.offset + KeyValue.ROW_KEY_OFFSET;
+  }
+
+  @Override
+  public ByteBuffer getFamilyByteBuffer() {
+    return this.buf;
+  }
+
+  @Override
+  public int getFamilyPositionInByteBuffer() {
+    return getFamilyLengthPosition() + Bytes.SIZEOF_BYTE;
+  }
+
+  @Override
+  public ByteBuffer getQualifierByteBuffer() {
+    return this.buf;
+  }
+
+  @Override
+  public int getQualifierPositionInByteBuffer() {
+    return getFamilyPositionInByteBuffer() + getFamilyLength();
+  }
+
+  @Override
+  public ByteBuffer getValueByteBuffer() {
+    return this.buf;
+  }
+
+  @Override
+  public int getValuePositionInByteBuffer() {
+    return this.offset + KeyValue.ROW_OFFSET + this.keyLen;
+  }
+
+  @Override
+  public ByteBuffer getTagsByteBuffer() {
+    return this.buf;
+  }
+
+  @Override
+  public int getTagsPositionInByteBuffer() {
+    int tagsLen = getTagsLength();
+    if (tagsLen == 0) {
+      return this.offset + this.length;
+    }
+    return this.offset + this.length - tagsLen;
+  }
+
+  @Override
+  public long heapSize() {
+    return ClassSize.align(FIXED_HEAP_SIZE_OVERHEAD + ClassSize.align(length));
+  }
+
+  @Override
+  public int write(OutputStream out) throws IOException {
+    return write(out, true);
+  }
+
+  @Override
+  public int write(OutputStream out, boolean withTags) throws IOException {
+    // In KeyValueUtil#oswrite we do a Cell serialization as KeyValue. Any
+    // changes doing here, pls check KeyValueUtil#oswrite also and do necessary changes.
+    int length = this.length;
+    if (hasTags && !withTags) {
+      length = keyLen + this.getValueLength() + KeyValue.KEYVALUE_INFRASTRUCTURE_SIZE;
+    }
+    ByteBufferUtils.putInt(out, length);
+    ByteBufferUtils.writeByteBuffer(out, this.buf, this.offset, length);
+    return length + Bytes.SIZEOF_INT;
+  }
+
+  @Override
+  public String toString() {
+    return CellUtil.toString(this, true);
+  }
+}

hbase-common/src/main/java/org/apache/hadoop/hbase/io/encoding/BufferedDataBlockEncoder.java

@@ -28,13 +28,12 @@ import org.apache.hadoop.hbase.CellComparator;
 import org.apache.hadoop.hbase.CellUtil;
 import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.KeyValue;
-import org.apache.hadoop.hbase.OffheapKeyOnlyKeyValue;
+import org.apache.hadoop.hbase.ByteBufferedKeyOnlyKeyValue;
 import org.apache.hadoop.hbase.KeyValue.Type;
 import org.apache.hadoop.hbase.KeyValueUtil;
 import org.apache.hadoop.hbase.SettableSequenceId;
 import org.apache.hadoop.hbase.Streamable;
 import org.apache.hadoop.hbase.classification.InterfaceAudience;
-import org.apache.hadoop.hbase.io.ByteBufferOutputStream;
 import org.apache.hadoop.hbase.io.HeapSize;
 import org.apache.hadoop.hbase.io.TagCompressionContext;
 import org.apache.hadoop.hbase.io.hfile.BlockType;
@@ -445,9 +444,9 @@ abstract class BufferedDataBlockEncoder implements DataBlockEncoder {
     public int write(OutputStream out, boolean withTags) throws IOException {
       int lenToWrite = KeyValueUtil.length(rowLength, familyLength, qualifierLength, valueLength,
           tagsLength, withTags);
-      writeInt(out, lenToWrite);
-      writeInt(out, keyOnlyBuffer.length);
-      writeInt(out, valueLength);
+      ByteBufferUtils.putInt(out, lenToWrite);
+      ByteBufferUtils.putInt(out, keyOnlyBuffer.length);
+      ByteBufferUtils.putInt(out, valueLength);
       // Write key
       out.write(keyOnlyBuffer);
       // Write value
@@ -668,47 +667,25 @@ abstract class BufferedDataBlockEncoder implements DataBlockEncoder {
     public int write(OutputStream out, boolean withTags) throws IOException {
       int lenToWrite = KeyValueUtil.length(rowLength, familyLength, qualifierLength, valueLength,
           tagsLength, withTags);
-      writeInt(out, lenToWrite);
-      writeInt(out, keyBuffer.capacity());
-      writeInt(out, valueLength);
+      ByteBufferUtils.putInt(out, lenToWrite);
+      ByteBufferUtils.putInt(out, keyBuffer.capacity());
+      ByteBufferUtils.putInt(out, valueLength);
       // Write key
       out.write(keyBuffer.array());
       // Write value
-      writeByteBuffer(out, this.valueBuffer, this.valueOffset, this.valueLength);
+      ByteBufferUtils.writeByteBuffer(out, this.valueBuffer, this.valueOffset, this.valueLength);
       if (withTags) {
         // 2 bytes tags length followed by tags bytes
         // tags length is serialized with 2 bytes only(short way) even if the type is int.
         // As this is non -ve numbers, we save the sign bit. See HBASE-11437
         out.write((byte) (0xff & (this.tagsLength >> 8)));
         out.write((byte) (0xff & this.tagsLength));
-        writeByteBuffer(out, this.tagsBuffer, this.tagsOffset, this.tagsLength);
+        ByteBufferUtils.writeByteBuffer(out, this.tagsBuffer, this.tagsOffset, this.tagsLength);
       }
       return lenToWrite + Bytes.SIZEOF_INT;
     }
   }
 
-  private static void writeInt(OutputStream out, int v) throws IOException {
-    // We have writeInt in ByteBufferOutputStream so that it can directly write int to underlying
-    // ByteBuffer in one step.
-    if (out instanceof ByteBufferOutputStream) {
-      ((ByteBufferOutputStream) out).writeInt(v);
-    } else {
-      StreamUtils.writeInt(out, v);
-    }
-  }
-
-  private static void writeByteBuffer(OutputStream out, ByteBuffer b, int offset, int length)
-      throws IOException {
-    // We have write which takes ByteBuffer in ByteBufferOutputStream so that it can directly write
-    // bytes from the src ByteBuffer to the destination ByteBuffer. This avoid need for temp array
-    // creation and copy
-    if (out instanceof ByteBufferOutputStream) {
-      ((ByteBufferOutputStream) out).write(b, offset, length);
-    } else {
-      ByteBufferUtils.copyBufferToStream(out, b, offset, length);
-    }
-  }
-
   protected abstract static class
       BufferedEncodedSeeker<STATE extends SeekerState>
       implements EncodedSeeker {
@@ -1166,7 +1143,7 @@ abstract class BufferedDataBlockEncoder implements DataBlockEncoder {
         }
       }
     }
-    ByteBufferUtils.putInt(out, 0); // DUMMY length. This will be updated in endBlockEncoding()
+    StreamUtils.writeInt(out, 0); // DUMMY length. This will be updated in endBlockEncoding()
     blkEncodingCtx.setEncodingState(new BufferedDataBlockEncodingState());
   }
 
@@ -1208,7 +1185,7 @@ abstract class BufferedDataBlockEncoder implements DataBlockEncoder {
       return new KeyValue.KeyOnlyKeyValue(key.array(), key.arrayOffset() + key.position(),
           keyLength);
     } else {
-      return new OffheapKeyOnlyKeyValue(key, key.position(), keyLength);
+      return new ByteBufferedKeyOnlyKeyValue(key, key.position(), keyLength);
     }
   }
 }

hbase-common/src/main/java/org/apache/hadoop/hbase/util/ByteBufferUtils.java

@@ -27,6 +27,8 @@ import java.nio.ByteBuffer;
 
 import org.apache.hadoop.hbase.classification.InterfaceAudience;
 import org.apache.hadoop.hbase.classification.InterfaceStability;
+import org.apache.hadoop.hbase.io.ByteBufferOutputStream;
+import org.apache.hadoop.hbase.io.util.StreamUtils;
 import org.apache.hadoop.io.IOUtils;
 import org.apache.hadoop.io.WritableUtils;
 
@@ -134,8 +136,13 @@ public final class ByteBufferUtils {
     */
    public static void putInt(OutputStream out, final int value)
        throws IOException {
-     for (int i = Bytes.SIZEOF_INT - 1; i >= 0; --i) {
-       out.write((byte) (value >>> (i * 8)));
+     // We have writeInt in ByteBufferOutputStream so that it can directly write
+     // int to underlying
+     // ByteBuffer in one step.
+     if (out instanceof ByteBufferOutputStream) {
+       ((ByteBufferOutputStream) out).writeInt(value);
+     } else {
+       StreamUtils.writeInt(out, value);
      }
    }
 
@@ -829,4 +836,41 @@ public final class ByteBufferUtils {
       }
     }
   }
+
+  public static void writeByteBuffer(OutputStream out, ByteBuffer b, int offset, int length)
+      throws IOException {
+    // We have write which takes ByteBuffer in ByteBufferOutputStream so that it
+    // can directly write
+    // bytes from the src ByteBuffer to the destination ByteBuffer. This avoid
+    // need for temp array
+    // creation and copy
+    if (out instanceof ByteBufferOutputStream) {
+      ((ByteBufferOutputStream) out).write(b, offset, length);
+    } else {
+      ByteBufferUtils.copyBufferToStream(out, b, offset, length);
+    }
+  }
+  // For testing purpose
+  public static String toStringBinary(final ByteBuffer b, int off, int len) {
+    StringBuilder result = new StringBuilder();
+    // Just in case we are passed a 'len' that is > buffer length...
+    if (off >= b.capacity())
+      return result.toString();
+    if (off + len > b.capacity())
+      len = b.capacity() - off;
+    for (int i = off; i < off + len; ++i) {
+      int ch = b.get(i) & 0xFF;
+      if ((ch >= '0' && ch <= '9') || (ch >= 'A' && ch <= 'Z') || (ch >= 'a' && ch <= 'z')
+          || " `~!@#$%^&*()-_=+[]{}|;:'\",.<>/?".indexOf(ch) >= 0) {
+        result.append((char) ch);
+      } else {
+        result.append(String.format("\\x%02X", ch));
+      }
+    }
+    return result.toString();
+  }
+
+  public static String toStringBinary(final ByteBuffer b) {
+    return toStringBinary(b, 0, b.capacity());
+  }
 }

hbase-common/src/test/java/org/apache/hadoop/hbase/TestOffheapKeyValue.java

@@ -0,0 +1,205 @@
+/*
+ * 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.hadoop.hbase;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+import java.nio.ByteBuffer;
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.hadoop.hbase.KeyValue.Type;
+import org.apache.hadoop.hbase.testclassification.MiscTests;
+import org.apache.hadoop.hbase.testclassification.SmallTests;
+import org.apache.hadoop.hbase.util.ByteBufferUtils;
+import org.apache.hadoop.hbase.util.Bytes;
+import org.junit.Test;
+import org.junit.experimental.categories.Category;
+
+@Category({ MiscTests.class, SmallTests.class })
+public class TestOffheapKeyValue {
+  private static final String QUAL2 = "qual2";
+  private static final String FAM2 = "fam2";
+  private static final String QUAL1 = "qual1";
+  private static final String FAM1 = "fam1";
+  private static final String ROW1 = "row1";
+  private static final byte[] row1 = Bytes.toBytes(ROW1);
+  private static final byte[] fam1 = Bytes.toBytes(FAM1);
+  private static final byte[] fam2 = Bytes.toBytes(FAM2);
+  private static final byte[] qual1 = Bytes.toBytes(QUAL1);
+  private static final byte[] qual2 = Bytes.toBytes(QUAL2);
+  private static final Tag t1 = new Tag((byte) 1, Bytes.toBytes("TAG1"));
+  private static final Tag t2 = new Tag((byte) 2, Bytes.toBytes("TAG2"));
+  private static final ArrayList<Tag> tags = new ArrayList<Tag>();
+  static {
+    tags.add(t1);
+    tags.add(t2);
+  }
+
+  @Test
+  public void testByteBufferBackedKeyValue() throws Exception {
+    KeyValue kvCell = new KeyValue(row1, fam1, qual1, 0l, Type.Put, row1);
+    ByteBuffer buf = ByteBuffer.allocateDirect(kvCell.getBuffer().length);
+    ByteBufferUtils.copyFromArrayToBuffer(buf, kvCell.getBuffer(), 0, kvCell.getBuffer().length);
+    ByteBufferedCell offheapKV = new OffheapKeyValue(buf, 0, buf.capacity(), false);
+    assertEquals(
+      ROW1,
+      ByteBufferUtils.toStringBinary(offheapKV.getRowByteBuffer(),
+        offheapKV.getRowPositionInByteBuffer(), offheapKV.getRowLength()));
+    assertEquals(
+      FAM1,
+      ByteBufferUtils.toStringBinary(offheapKV.getFamilyByteBuffer(),
+        offheapKV.getFamilyPositionInByteBuffer(), offheapKV.getFamilyLength()));
+    assertEquals(
+      QUAL1,
+      ByteBufferUtils.toStringBinary(offheapKV.getQualifierByteBuffer(),
+        offheapKV.getQualifierPositionInByteBuffer(), offheapKV.getQualifierLength()));
+    assertEquals(
+      ROW1,
+      ByteBufferUtils.toStringBinary(offheapKV.getValueByteBuffer(),
+        offheapKV.getValuePositionInByteBuffer(), offheapKV.getValueLength()));
+    assertEquals(0L, offheapKV.getTimestamp());
+    assertEquals(Type.Put.getCode(), offheapKV.getTypeByte());
+
+    // Use the array() APIs
+    assertEquals(
+      ROW1,
+      Bytes.toStringBinary(offheapKV.getRowArray(),
+        offheapKV.getRowOffset(), offheapKV.getRowLength()));
+    assertEquals(
+      FAM1,
+      Bytes.toStringBinary(offheapKV.getFamilyArray(),
+        offheapKV.getFamilyOffset(), offheapKV.getFamilyLength()));
+    assertEquals(
+      QUAL1,
+      Bytes.toStringBinary(offheapKV.getQualifierArray(),
+        offheapKV.getQualifierOffset(), offheapKV.getQualifierLength()));
+    assertEquals(
+      ROW1,
+      Bytes.toStringBinary(offheapKV.getValueArray(),
+        offheapKV.getValueOffset(), offheapKV.getValueLength()));
+    assertEquals(0L, offheapKV.getTimestamp());
+    assertEquals(Type.Put.getCode(), offheapKV.getTypeByte());
+
+    kvCell = new KeyValue(row1, fam2, qual2, 0l, Type.Put, row1);
+    buf = ByteBuffer.allocateDirect(kvCell.getBuffer().length);
+    ByteBufferUtils.copyFromArrayToBuffer(buf, kvCell.getBuffer(), 0, kvCell.getBuffer().length);
+    offheapKV = new OffheapKeyValue(buf, 0, buf.capacity(), false);
+    assertEquals(
+      FAM2,
+      ByteBufferUtils.toStringBinary(offheapKV.getFamilyByteBuffer(),
+        offheapKV.getFamilyPositionInByteBuffer(), offheapKV.getFamilyLength()));
+    assertEquals(
+      QUAL2,
+      ByteBufferUtils.toStringBinary(offheapKV.getQualifierByteBuffer(),
+        offheapKV.getQualifierPositionInByteBuffer(), offheapKV.getQualifierLength()));
+    byte[] nullQualifier = new byte[0];
+    kvCell = new KeyValue(row1, fam1, nullQualifier, 0L, Type.Put, row1);
+    buf = ByteBuffer.allocateDirect(kvCell.getBuffer().length);
+    ByteBufferUtils.copyFromArrayToBuffer(buf, kvCell.getBuffer(), 0, kvCell.getBuffer().length);
+    offheapKV = new OffheapKeyValue(buf, 0, buf.capacity(), false);
+    assertEquals(
+      ROW1,
+      ByteBufferUtils.toStringBinary(offheapKV.getRowByteBuffer(),
+        offheapKV.getRowPositionInByteBuffer(), offheapKV.getRowLength()));
+    assertEquals(
+      FAM1,
+      ByteBufferUtils.toStringBinary(offheapKV.getFamilyByteBuffer(),
+        offheapKV.getFamilyPositionInByteBuffer(), offheapKV.getFamilyLength()));
+    assertEquals(
+      "",
+      ByteBufferUtils.toStringBinary(offheapKV.getQualifierByteBuffer(),
+        offheapKV.getQualifierPositionInByteBuffer(), offheapKV.getQualifierLength()));
+    assertEquals(
+      ROW1,
+      ByteBufferUtils.toStringBinary(offheapKV.getValueByteBuffer(),
+        offheapKV.getValuePositionInByteBuffer(), offheapKV.getValueLength()));
+    assertEquals(0L, offheapKV.getTimestamp());
+    assertEquals(Type.Put.getCode(), offheapKV.getTypeByte());
+  }
+
+  @Test
+  public void testByteBufferBackedKeyValueWithTags() throws Exception {
+    KeyValue kvCell = new KeyValue(row1, fam1, qual1, 0l, Type.Put, row1, tags);
+    ByteBuffer buf = ByteBuffer.allocateDirect(kvCell.getBuffer().length);
+    ByteBufferUtils.copyFromArrayToBuffer(buf, kvCell.getBuffer(), 0, kvCell.getBuffer().length);
+    ByteBufferedCell offheapKV = new OffheapKeyValue(buf, 0, buf.capacity(), true);
+    assertEquals(
+      ROW1,
+      ByteBufferUtils.toStringBinary(offheapKV.getRowByteBuffer(),
+        offheapKV.getRowPositionInByteBuffer(), offheapKV.getRowLength()));
+    assertEquals(
+      FAM1,
+      ByteBufferUtils.toStringBinary(offheapKV.getFamilyByteBuffer(),
+        offheapKV.getFamilyPositionInByteBuffer(), offheapKV.getFamilyLength()));
+    assertEquals(
+      QUAL1,
+      ByteBufferUtils.toStringBinary(offheapKV.getQualifierByteBuffer(),
+        offheapKV.getQualifierPositionInByteBuffer(), offheapKV.getQualifierLength()));
+    assertEquals(
+      ROW1,
+      ByteBufferUtils.toStringBinary(offheapKV.getValueByteBuffer(),
+        offheapKV.getValuePositionInByteBuffer(), offheapKV.getValueLength()));
+    assertEquals(0L, offheapKV.getTimestamp());
+    assertEquals(Type.Put.getCode(), offheapKV.getTypeByte());
+    // change tags to handle both onheap and offheap stuff
+    List<Tag> resTags =
+        Tag.asList(offheapKV.getTagsArray(), offheapKV.getTagsOffset(), offheapKV.getTagsLength());
+    Tag tag1 = resTags.get(0);
+    assertEquals(t1.getType(), tag1.getType());
+    assertEquals(Bytes.toString(t1.getValue()), Bytes.toString(getTagValue(tag1)));
+    Tag tag2 = resTags.get(1);
+    assertEquals(tag2.getType(), tag2.getType());
+    assertEquals(Bytes.toString(t2.getValue()), Bytes.toString(getTagValue(tag2)));
+    Tag res = Tag.getTag(offheapKV.getTagsArray(), 0, offheapKV.getTagsLength(), (byte) 2);
+    assertEquals(Bytes.toString(t2.getValue()), Bytes.toString(getTagValue(tag2)));
+    res = Tag.getTag(offheapKV.getTagsArray(), 0, offheapKV.getTagsLength(), (byte) 3);
+    assertNull(res);
+  }
+
+  @Test
+  public void testGetKeyMethods() throws Exception {
+    KeyValue kvCell = new KeyValue(row1, fam1, qual1, 0l, Type.Put, row1, tags);
+    ByteBuffer buf = ByteBuffer.allocateDirect(kvCell.getKeyLength());
+    ByteBufferUtils.copyFromArrayToBuffer(buf, kvCell.getBuffer(), kvCell.getKeyOffset(),
+      kvCell.getKeyLength());
+    ByteBufferedCell offheapKeyOnlyKV = new ByteBufferedKeyOnlyKeyValue(buf, 0, buf.capacity());
+    assertEquals(
+      ROW1,
+      ByteBufferUtils.toStringBinary(offheapKeyOnlyKV.getRowByteBuffer(),
+        offheapKeyOnlyKV.getRowPositionInByteBuffer(), offheapKeyOnlyKV.getRowLength()));
+    assertEquals(
+      FAM1,
+      ByteBufferUtils.toStringBinary(offheapKeyOnlyKV.getFamilyByteBuffer(),
+        offheapKeyOnlyKV.getFamilyPositionInByteBuffer(), offheapKeyOnlyKV.getFamilyLength()));
+    assertEquals(
+      QUAL1,
+      ByteBufferUtils.toStringBinary(offheapKeyOnlyKV.getQualifierByteBuffer(),
+        offheapKeyOnlyKV.getQualifierPositionInByteBuffer(),
+        offheapKeyOnlyKV.getQualifierLength()));
+    assertEquals(0L, offheapKeyOnlyKV.getTimestamp());
+    assertEquals(Type.Put.getCode(), offheapKeyOnlyKV.getTypeByte());
+  }
+  // TODO : Can be moved to TagUtil
+  private static byte[] getTagValue(Tag tag) {
+    int tagLength = tag.getTagLength();
+    byte[] tagBytes = new byte[tagLength];
+    System.arraycopy(tag.getBuffer(), tag.getTagOffset(), tagBytes, 0, tagLength);
+    return tagBytes;
+  }
+}

hbase-server/src/main/java/org/apache/hadoop/hbase/SizeCachedNoTagsKeyValue.java

@@ -23,6 +23,7 @@ import java.io.IOException;
 import java.io.OutputStream;
 
 import org.apache.hadoop.hbase.classification.InterfaceAudience;
+import org.apache.hadoop.hbase.util.ByteBufferUtils;
 import org.apache.hadoop.hbase.util.Bytes;
 
 /**
@@ -44,7 +45,7 @@ public class SizeCachedNoTagsKeyValue extends SizeCachedKeyValue {
 
   @Override
   public int write(OutputStream out, boolean withTags) throws IOException {
-    writeInt(out, this.length);
+    ByteBufferUtils.putInt(out, this.length);
     out.write(this.bytes, this.offset, this.length);
     return this.length + Bytes.SIZEOF_INT;
   }

hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileBlockIndex.java

@@ -41,6 +41,7 @@ import org.apache.hadoop.hbase.HConstants;
 import org.apache.hadoop.hbase.KeyValue;
 import org.apache.hadoop.hbase.KeyValue.KeyOnlyKeyValue;
 import org.apache.hadoop.hbase.KeyValueUtil;
+import org.apache.hadoop.hbase.ByteBufferedKeyOnlyKeyValue;
 import org.apache.hadoop.hbase.classification.InterfaceAudience;
 import org.apache.hadoop.hbase.io.HeapSize;
 import org.apache.hadoop.hbase.io.encoding.DataBlockEncoding;
@@ -728,7 +729,7 @@ public class HFileBlockIndex {
       // If we imagine that keys[-1] = -Infinity and
       // keys[numEntries] = Infinity, then we are maintaining an invariant that
       // keys[low - 1] < key < keys[high + 1] while narrowing down the range.
-      KeyValue.KeyOnlyKeyValue nonRootIndexKV = new KeyValue.KeyOnlyKeyValue();
+      ByteBufferedKeyOnlyKeyValue nonRootIndexkeyOnlyKV = new ByteBufferedKeyOnlyKeyValue();
       Pair<ByteBuffer, Integer> pair = new Pair<ByteBuffer, Integer>();
       while (low <= high) {
         mid = (low + high) >>> 1;
@@ -753,9 +754,8 @@ public class HFileBlockIndex {
         // done after HBASE-12224 & HBASE-12282
         // TODO avoid array call.
         nonRootIndex.asSubByteBuffer(midKeyOffset, midLength, pair);
-        nonRootIndexKV.setKey(pair.getFirst().array(),
-            pair.getFirst().arrayOffset() + pair.getSecond(), midLength);
-        int cmp = comparator.compareKeyIgnoresMvcc(key, nonRootIndexKV);
+        nonRootIndexkeyOnlyKV.setKey(pair.getFirst(), pair.getSecond(), midLength);
+        int cmp = comparator.compareKeyIgnoresMvcc(key, nonRootIndexkeyOnlyKV);
 
         // key lives above the midpoint
         if (cmp > 0)

hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/HFileReaderImpl.java

@@ -34,6 +34,8 @@ import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.hbase.Cell;
 import org.apache.hadoop.hbase.CellComparator;
 import org.apache.hadoop.hbase.CellUtil;
+import org.apache.hadoop.hbase.ByteBufferedKeyOnlyKeyValue;
+import org.apache.hadoop.hbase.OffheapKeyValue;
 import org.apache.hadoop.hbase.ShareableMemory;
 import org.apache.hadoop.hbase.SizeCachedKeyValue;
 import org.apache.hadoop.hbase.HConstants;
@@ -52,6 +54,7 @@ import org.apache.hadoop.hbase.io.hfile.HFile.FileInfo;
 import org.apache.hadoop.hbase.nio.ByteBuff;
 import org.apache.hadoop.hbase.security.EncryptionUtil;
 import org.apache.hadoop.hbase.security.User;
+import org.apache.hadoop.hbase.util.ByteBufferUtils;
 import org.apache.hadoop.hbase.util.Bytes;
 import org.apache.hadoop.hbase.util.IdLock;
 import org.apache.hadoop.hbase.util.Pair;
@@ -464,7 +467,8 @@ public class HFileReaderImpl implements HFile.Reader, Configurable {
     protected volatile int blockFetches;
     protected final HFile.Reader reader;
     private int currTagsLen;
-    private KeyValue.KeyOnlyKeyValue keyOnlyKv = new KeyValue.KeyOnlyKeyValue();
+    // buffer backed keyonlyKV
+    private ByteBufferedKeyOnlyKeyValue bufBackedKeyOnlyKv = new ByteBufferedKeyOnlyKeyValue();
     // A pair for reusing in blockSeek() so that we don't garbage lot of objects
     final Pair<ByteBuffer, Integer> pair = new Pair<ByteBuffer, Integer>();
 
@@ -675,10 +679,8 @@ public class HFileReaderImpl implements HFile.Reader, Configurable {
         }
         offsetFromPos += Bytes.SIZEOF_LONG;
         blockBuffer.asSubByteBuffer(blockBuffer.position() + offsetFromPos, klen, pair);
-        // TODO :change here after Bufferbackedcells come
-        keyOnlyKv.setKey(pair.getFirst().array(), pair.getFirst().arrayOffset() + pair.getSecond(),
-            klen);
-        int comp = reader.getComparator().compareKeyIgnoresMvcc(key, keyOnlyKv);
+        bufBackedKeyOnlyKv.setKey(pair.getFirst(), pair.getSecond(), klen);
+        int comp = reader.getComparator().compareKeyIgnoresMvcc(key, bufBackedKeyOnlyKv);
         offsetFromPos += klen + vlen;
         if (this.reader.getFileContext().isIncludesTags()) {
           // Read short as unsigned, high byte first
@@ -888,30 +890,43 @@ public class HFileReaderImpl implements HFile.Reader, Configurable {
       if (!isSeeked())
         return null;
 
-      KeyValue ret;
-      // TODO : reduce the varieties of KV here. Check if based on a boolean
-      // we can handle the 'no tags' case
-      // TODO : Handle MBB here
-      if (currTagsLen > 0) {
-        if (this.curBlock.getMemoryType() == MemoryType.SHARED) {
-          ret = new ShareableMemoryKeyValue(blockBuffer.array(), blockBuffer.arrayOffset()
-                          + blockBuffer.position(), getCellBufSize());
+      Cell ret;
+      int cellBufSize = getCellBufSize();
+      if (blockBuffer.hasArray()) {
+        // TODO : reduce the varieties of KV here. Check if based on a boolean
+        // we can handle the 'no tags' case.
+        if (currTagsLen > 0) {
+          if (this.curBlock.getMemoryType() == MemoryType.SHARED) {
+            ret = new ShareableMemoryKeyValue(blockBuffer.array(), blockBuffer.arrayOffset()
+              + blockBuffer.position(), getCellBufSize());
+          } else {
+            ret = new SizeCachedKeyValue(blockBuffer.array(), blockBuffer.arrayOffset()
+                    + blockBuffer.position(), cellBufSize);
+          }
         } else {
-          ret = new SizeCachedKeyValue(blockBuffer.array(), blockBuffer.arrayOffset()
-                  + blockBuffer.position(), getCellBufSize());
+          if (this.curBlock.getMemoryType() == MemoryType.SHARED) {
+            ret = new ShareableMemoryNoTagsKeyValue(blockBuffer.array(), blockBuffer.arrayOffset()
+                    + blockBuffer.position(), getCellBufSize());
+          } else {
+            ret = new SizeCachedNoTagsKeyValue(blockBuffer.array(), blockBuffer.arrayOffset()
+                    + blockBuffer.position(), cellBufSize);
+          }
         }
       } else {
+        ByteBuffer buf = blockBuffer.asSubByteBuffer(cellBufSize);
         if (this.curBlock.getMemoryType() == MemoryType.SHARED) {
-          ret = new ShareableMemoryNoTagsKeyValue(blockBuffer.array(), blockBuffer.arrayOffset()
-            + blockBuffer.position(), getCellBufSize());
+          ret = new ShareableMemoryOffheapKeyValue(buf, buf.position(), cellBufSize,
+            currTagsLen > 0);
         } else {
-          ret = new SizeCachedNoTagsKeyValue(blockBuffer.array(), blockBuffer.arrayOffset()
-            + blockBuffer.position(), getCellBufSize());
+          ret = new OffheapKeyValue(buf, buf.position(), cellBufSize, currTagsLen > 0);
         }
       }
-
       if (this.reader.shouldIncludeMemstoreTS()) {
-        ret.setSequenceId(currMemstoreTS);
+        try {
+          CellUtil.setSequenceId(ret, currMemstoreTS);
+        } catch (IOException e) {
+          // will not happen
+        }
       }
       return ret;
     }
@@ -919,9 +934,16 @@ public class HFileReaderImpl implements HFile.Reader, Configurable {
     @Override
     public Cell getKey() {
       assertSeeked();
-      return new KeyValue.KeyOnlyKeyValue(blockBuffer.array(),
-          blockBuffer.arrayOffset() + blockBuffer.position()
-              + KEY_VALUE_LEN_SIZE, currKeyLen);
+      // Create a new object so that this getKey is cached as firstKey, lastKey
+      Pair<ByteBuffer, Integer> keyPair = new Pair<ByteBuffer, Integer>();
+      blockBuffer.asSubByteBuffer(blockBuffer.position() + KEY_VALUE_LEN_SIZE, currKeyLen, keyPair);
+      ByteBuffer keyBuf = keyPair.getFirst();
+      if (keyBuf.hasArray()) {
+        return new KeyValue.KeyOnlyKeyValue(keyBuf.array(), keyBuf.arrayOffset()
+            + keyPair.getSecond(), currKeyLen);
+      } else {
+        return new ByteBufferedKeyOnlyKeyValue(keyBuf, keyPair.getSecond(), currKeyLen);
+      }
     }
 
     private static class ShareableMemoryKeyValue extends SizeCachedKeyValue implements
@@ -950,14 +972,32 @@ public class HFileReaderImpl implements HFile.Reader, Configurable {
       }
     }
 
+    private static class ShareableMemoryOffheapKeyValue extends OffheapKeyValue implements
+        ShareableMemory {
+      public ShareableMemoryOffheapKeyValue(ByteBuffer buf, int offset, int length,
+          boolean hasTags) {
+        super(buf, offset, length, hasTags);
+      }
+
+      @Override
+      public Cell cloneToCell() {
+        byte[] copy = new byte[this.length];
+        ByteBufferUtils.copyFromBufferToArray(copy, this.buf, this.offset, 0, this.length);
+        return new SizeCachedKeyValue(copy, 0, copy.length);
+      }
+    }
+
     @Override
     public ByteBuffer getValue() {
       assertSeeked();
-      // TODO : change here after BufferBacked cells come
-      return ByteBuffer.wrap(
-          blockBuffer.array(),
-          blockBuffer.arrayOffset() + blockBuffer.position()
-              + KEY_VALUE_LEN_SIZE + currKeyLen, currValueLen).slice();
+      // Okie to create new Pair. Not used in hot path
+      Pair<ByteBuffer, Integer> valuePair = new Pair<ByteBuffer, Integer>();
+      this.blockBuffer.asSubByteBuffer(blockBuffer.position() + KEY_VALUE_LEN_SIZE + currKeyLen,
+        currValueLen, valuePair);
+      ByteBuffer valBuf = valuePair.getFirst().duplicate();
+      valBuf.position(valuePair.getSecond());
+      valBuf.limit(currValueLen + valuePair.getSecond());
+      return valBuf.slice();
     }
 
     protected void setNonSeekedState() {
@@ -1151,32 +1191,28 @@ public class HFileReaderImpl implements HFile.Reader, Configurable {
       int klen = buffer.getInt();
       buffer.skip(Bytes.SIZEOF_INT);// Skip value len part
       ByteBuffer keyBuff = buffer.asSubByteBuffer(klen);
-      keyBuff.limit(keyBuff.position() + klen);
-      // Create a KeyOnlyKv now.
-      // TODO : Will change when Buffer backed cells come
-      return new KeyValue.KeyOnlyKeyValue(keyBuff.array(), keyBuff.arrayOffset()
-          + keyBuff.position(), klen);
+      if (keyBuff.hasArray()) {
+        return new KeyValue.KeyOnlyKeyValue(keyBuff.array(), keyBuff.arrayOffset()
+            + keyBuff.position(), klen);
+      } else {
+        return new ByteBufferedKeyOnlyKeyValue(keyBuff, keyBuff.position(), klen);
+      }
     }
 
     @Override
     public String getKeyString() {
-      return Bytes.toStringBinary(blockBuffer.array(),
-          blockBuffer.arrayOffset() + blockBuffer.position()
-              + KEY_VALUE_LEN_SIZE, currKeyLen);
+      return CellUtil.toString(getKey(), false);
     }
 
     @Override
     public String getValueString() {
-      return Bytes.toString(blockBuffer.array(), blockBuffer.arrayOffset()
-          + blockBuffer.position() + KEY_VALUE_LEN_SIZE + currKeyLen,
-          currValueLen);
+      return ByteBufferUtils.toStringBinary(getValue());
     }
 
     public int compareKey(CellComparator comparator, Cell key) {
-      this.keyOnlyKv.setKey(blockBuffer.array(), blockBuffer.arrayOffset()
-              + blockBuffer.position() + KEY_VALUE_LEN_SIZE, currKeyLen);
-      return comparator.compareKeyIgnoresMvcc(
-          key, this.keyOnlyKv);
+      blockBuffer.asSubByteBuffer(blockBuffer.position() + KEY_VALUE_LEN_SIZE, currKeyLen, pair);
+      this.bufBackedKeyOnlyKv.setKey(pair.getFirst(), pair.getSecond(), currKeyLen);
+      return comparator.compareKeyIgnoresMvcc(key, this.bufBackedKeyOnlyKv);
     }
 
     @Override
@@ -1534,7 +1570,6 @@ public class HFileReaderImpl implements HFile.Reader, Configurable {
     private final HFileBlockDecodingContext decodingCtx;
     private final DataBlockEncoder.EncodedSeeker seeker;
     private final DataBlockEncoder dataBlockEncoder;
-    private final HFileContext meta;
 
     public EncodedScanner(HFile.Reader reader, boolean cacheBlocks,
         boolean pread, boolean isCompaction, HFileContext meta) {
@@ -1544,7 +1579,6 @@ public class HFileReaderImpl implements HFile.Reader, Configurable {
       decodingCtx = dataBlockEncoder.newDataBlockDecodingContext(meta);
       seeker = dataBlockEncoder.createSeeker(
         reader.getComparator(), decodingCtx);
-      this.meta = meta;
     }
 
     @Override
@@ -1644,8 +1678,7 @@ public class HFileReaderImpl implements HFile.Reader, Configurable {
     @Override
     public String getValueString() {
       ByteBuffer valueBuffer = getValue();
-      return Bytes.toStringBinary(valueBuffer.array(),
-          valueBuffer.arrayOffset(), valueBuffer.limit());
+      return ByteBufferUtils.toStringBinary(valueBuffer);
     }
 
     private void assertValidSeek() {
@@ -1708,22 +1741,6 @@ public class HFileReaderImpl implements HFile.Reader, Configurable {
     return true; // We load file info in constructor in version 2.
   }
 
-  /**
-   * Validates that the minor version is within acceptable limits.
-   * Otherwise throws an Runtime exception
-   */
-  private void validateMinorVersion(Path path, int minorVersion) {
-    if (minorVersion < MIN_MINOR_VERSION ||
-        minorVersion > MAX_MINOR_VERSION) {
-      String msg = "Minor version for path " + path +
-                   " is expected to be between " +
-                   MIN_MINOR_VERSION + " and " + MAX_MINOR_VERSION +
-                   " but is found to be " + minorVersion;
-      LOG.error(msg);
-      throw new RuntimeException(msg);
-    }
-  }
-
   @Override
   public HFileContext getFileContext() {
     return hfileContext;

hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/bucket/ByteBufferIOEngine.java

@@ -24,7 +24,6 @@ import java.nio.ByteBuffer;
 import org.apache.hadoop.hbase.classification.InterfaceAudience;
 import org.apache.hadoop.hbase.io.hfile.Cacheable.MemoryType;
 import org.apache.hadoop.hbase.nio.ByteBuff;
-import org.apache.hadoop.hbase.nio.SingleByteBuff;
 import org.apache.hadoop.hbase.util.ByteBufferArray;
 import org.apache.hadoop.hbase.util.Pair;
 
@@ -69,22 +68,14 @@ public class ByteBufferIOEngine implements IOEngine {
 
   @Override
   public Pair<ByteBuff, MemoryType> read(long offset, int length) throws IOException {
-    // TODO : this allocate and copy will go away once we create BB backed cells
-    ByteBuffer dstBuffer = ByteBuffer.allocate(length);
-    bufferArray.getMultiple(offset, dstBuffer.remaining(), dstBuffer.array(),
-      dstBuffer.arrayOffset());
+    ByteBuff dstBuffer = bufferArray.asSubByteBuff(offset, length);
     // Here the buffer that is created directly refers to the buffer in the actual buckets.
     // When any cell is referring to the blocks created out of these buckets then it means that
     // those cells are referring to a shared memory area which if evicted by the BucketCache would
     // lead to corruption of results. Hence we set the type of the buffer as SHARED_MEMORY
     // so that the readers using this block are aware of this fact and do the necessary action
     // to prevent eviction till the results are either consumed or copied
-    if (dstBuffer.limit() != length) {
-      throw new RuntimeException("Only " + dstBuffer.limit() + " bytes read, " + length
-          + " expected");
-    }
-    // TODO : to be removed - make it conditional
-    return new Pair<ByteBuff, MemoryType>(new SingleByteBuff(dstBuffer), MemoryType.SHARED);
+    return new Pair<ByteBuff, MemoryType>(dstBuffer, MemoryType.SHARED);
   }
 
   /**

hbase-server/src/main/java/org/apache/hadoop/hbase/util/BloomFilterUtil.java

@@ -17,7 +17,6 @@
  */
 package org.apache.hadoop.hbase.util;
 
-import java.nio.ByteBuffer;
 import java.text.NumberFormat;
 import java.util.Random;
 

hbase-server/src/test/java/org/apache/hadoop/hbase/io/hfile/bucket/TestByteBufferIOEngine.java

@@ -107,10 +107,6 @@ public class TestByteBufferIOEngine {
         offset = (int) (Math.random() * (capacity - maxBlockSize));
       }
       ioEngine.write(srcBuffer, offset);
-      //ByteBuffer dstBuffer = ByteBuffer.allocate(blockSize);
-      //ioEngine.read(dstBuffer, offset);
-      //MultiByteBuffer read = new MultiByteBuffer(dstBuffer);
-      // TODO : this will get changed after HBASE-12295 goes in
       Pair<ByteBuff, MemoryType> read = ioEngine.read(offset, blockSize);
       for (int j = 0; j < byteArray.length; ++j) {
         assertTrue(srcBuffer.get(j) == read.getFirst().get(j));