Extend Java RocksDB iterators to support indirect Byte Buffers (#9222)

Summary:
Extend Java RocksDB iterators to support indirect byte buffers, to add to the existing support for direct byte buffers.
Code to distinguish direct/indirect buffers is switched in Java, and a 2nd separate JNI call implemented to support indirect
buffers. Indirect support passes contained buffers using byte[]

There are some Java subclasses of iterator (WBWIIterator, SstFileReaderIterator) which also now have parallel JNI support functions implemented, along with direct/indirect switches in Java methods.

Closes https://github.com/facebook/rocksdb/issues/6282

Pull Request resolved: https://github.com/facebook/rocksdb/pull/9222

Reviewed By: ajkr

Differential Revision: D35115283

Pulled By: jay-zhuang

fbshipit-source-id: f8d5d20b975aef700560fbcc99f707bb028dc42e

java/rocksjni/iterator.cc

@@ -6,13 +6,15 @@
 // This file implements the "bridge" between Java and C++ and enables
 // calling c++ ROCKSDB_NAMESPACE::Iterator methods from Java side.
 
+#include "rocksdb/iterator.h"
+
 #include <jni.h>
 #include <stdio.h>
 #include <stdlib.h>
+
 #include <algorithm>
 
 #include "include/org_rocksdb_RocksIterator.h"
-#include "rocksdb/iterator.h"
 #include "rocksjni/portal.h"
 
 /*
@@ -87,7 +89,7 @@ void Java_org_rocksdb_RocksIterator_prev0(JNIEnv* /*env*/, jobject /*jobj*/,
  * Signature: (J)V
  */
 void Java_org_rocksdb_RocksIterator_refresh0(JNIEnv* env, jobject /*jobj*/,
-                                            jlong handle) {
+                                             jlong handle) {
   auto* it = reinterpret_cast<ROCKSDB_NAMESPACE::Iterator*>(handle);
   ROCKSDB_NAMESPACE::Status s = it->Refresh();
 
@@ -106,19 +108,31 @@ void Java_org_rocksdb_RocksIterator_refresh0(JNIEnv* env, jobject /*jobj*/,
 void Java_org_rocksdb_RocksIterator_seek0(JNIEnv* env, jobject /*jobj*/,
                                           jlong handle, jbyteArray jtarget,
                                           jint jtarget_len) {
-  jbyte* target = env->GetByteArrayElements(jtarget, nullptr);
-  if (target == nullptr) {
-    // exception thrown: OutOfMemoryError
-    return;
-  }
-
-  ROCKSDB_NAMESPACE::Slice target_slice(reinterpret_cast<char*>(target),
-                                        jtarget_len);
-
   auto* it = reinterpret_cast<ROCKSDB_NAMESPACE::Iterator*>(handle);
-  it->Seek(target_slice);
+  auto seek = [&it](ROCKSDB_NAMESPACE::Slice& target_slice) {
+    it->Seek(target_slice);
+  };
+  ROCKSDB_NAMESPACE::JniUtil::k_op_region(seek, env, jtarget, 0, jtarget_len);
+}
 
-  env->ReleaseByteArrayElements(jtarget, target, JNI_ABORT);
+/*
+ * This method supports fetching into indirect byte buffers;
+ * the Java wrapper extracts the byte[] and passes it here.
+ * In this case, the buffer offset of the key may be non-zero.
+ *
+ * Class:     org_rocksdb_RocksIterator
+ * Method:    seek0
+ * Signature: (J[BII)V
+ */
+void Java_org_rocksdb_RocksIterator_seekByteArray0(
+    JNIEnv* env, jobject /*jobj*/, jlong handle, jbyteArray jtarget,
+    jint jtarget_off, jint jtarget_len) {
+  auto* it = reinterpret_cast<ROCKSDB_NAMESPACE::Iterator*>(handle);
+  auto seek = [&it](ROCKSDB_NAMESPACE::Slice& target_slice) {
+    it->Seek(target_slice);
+  };
+  ROCKSDB_NAMESPACE::JniUtil::k_op_region(seek, env, jtarget, jtarget_off,
+                                          jtarget_len);
 }
 
 /*
@@ -163,19 +177,31 @@ void Java_org_rocksdb_RocksIterator_seekForPrev0(JNIEnv* env, jobject /*jobj*/,
                                                  jlong handle,
                                                  jbyteArray jtarget,
                                                  jint jtarget_len) {
-  jbyte* target = env->GetByteArrayElements(jtarget, nullptr);
-  if (target == nullptr) {
-    // exception thrown: OutOfMemoryError
-    return;
-  }
-
-  ROCKSDB_NAMESPACE::Slice target_slice(reinterpret_cast<char*>(target),
-                                        jtarget_len);
-
   auto* it = reinterpret_cast<ROCKSDB_NAMESPACE::Iterator*>(handle);
-  it->SeekForPrev(target_slice);
+  auto seek = [&it](ROCKSDB_NAMESPACE::Slice& target_slice) {
+    it->SeekForPrev(target_slice);
+  };
+  ROCKSDB_NAMESPACE::JniUtil::k_op_region(seek, env, jtarget, 0, jtarget_len);
+}
 
-  env->ReleaseByteArrayElements(jtarget, target, JNI_ABORT);
+/*
+ * This method supports fetching into indirect byte buffers;
+ * the Java wrapper extracts the byte[] and passes it here.
+ * In this case, the buffer offset of the key may be non-zero.
+ *
+ * Class:     org_rocksdb_RocksIterator
+ * Method:    seek0
+ * Signature: (J[BII)V
+ */
+void Java_org_rocksdb_RocksIterator_seekForPrevByteArray0(
+    JNIEnv* env, jobject /*jobj*/, jlong handle, jbyteArray jtarget,
+    jint jtarget_off, jint jtarget_len) {
+  auto* it = reinterpret_cast<ROCKSDB_NAMESPACE::Iterator*>(handle);
+  auto seek = [&it](ROCKSDB_NAMESPACE::Slice& target_slice) {
+    it->SeekForPrev(target_slice);
+  };
+  ROCKSDB_NAMESPACE::JniUtil::k_op_region(seek, env, jtarget, jtarget_off,
+                                          jtarget_len);
 }
 
 /*
@@ -231,6 +257,29 @@ jint Java_org_rocksdb_RocksIterator_keyDirect0(JNIEnv* env, jobject /*jobj*/,
                                                   jtarget_off, jtarget_len);
 }
 
+/*
+ * This method supports fetching into indirect byte buffers;
+ * the Java wrapper extracts the byte[] and passes it here.
+ *
+ * Class:     org_rocksdb_RocksIterator
+ * Method:    keyByteArray0
+ * Signature: (J[BII)I
+ */
+jint Java_org_rocksdb_RocksIterator_keyByteArray0(JNIEnv* env, jobject /*jobj*/,
+                                                  jlong handle, jbyteArray jkey,
+                                                  jint jkey_off,
+                                                  jint jkey_len) {
+  auto* it = reinterpret_cast<ROCKSDB_NAMESPACE::Iterator*>(handle);
+  ROCKSDB_NAMESPACE::Slice key_slice = it->key();
+  jsize copy_size = std::min(static_cast<uint32_t>(key_slice.size()),
+                             static_cast<uint32_t>(jkey_len));
+  env->SetByteArrayRegion(
+      jkey, jkey_off, copy_size,
+      const_cast<jbyte*>(reinterpret_cast<const jbyte*>(key_slice.data())));
+
+  return static_cast<jsize>(key_slice.size());
+}
+
 /*
  * Class:     org_rocksdb_RocksIterator
  * Method:    value0
@@ -267,3 +316,25 @@ jint Java_org_rocksdb_RocksIterator_valueDirect0(JNIEnv* env, jobject /*jobj*/,
   return ROCKSDB_NAMESPACE::JniUtil::copyToDirect(env, value_slice, jtarget,
                                                   jtarget_off, jtarget_len);
 }
+
+/*
+ * This method supports fetching into indirect byte buffers;
+ * the Java wrapper extracts the byte[] and passes it here.
+ *
+ * Class:     org_rocksdb_RocksIterator
+ * Method:    valueByteArray0
+ * Signature: (J[BII)I
+ */
+jint Java_org_rocksdb_RocksIterator_valueByteArray0(
+    JNIEnv* env, jobject /*jobj*/, jlong handle, jbyteArray jvalue_target,
+    jint jvalue_off, jint jvalue_len) {
+  auto* it = reinterpret_cast<ROCKSDB_NAMESPACE::Iterator*>(handle);
+  ROCKSDB_NAMESPACE::Slice value_slice = it->value();
+  jsize copy_size = std::min(static_cast<uint32_t>(value_slice.size()),
+                             static_cast<uint32_t>(jvalue_len));
+  env->SetByteArrayRegion(
+      jvalue_target, jvalue_off, copy_size,
+      const_cast<jbyte*>(reinterpret_cast<const jbyte*>(value_slice.data())));
+
+  return static_cast<jsize>(value_slice.size());
+}

java/rocksjni/portal.h

@@ -2127,7 +2127,7 @@ class JniUtil {
         std::function<ROCKSDB_NAMESPACE::Status(ROCKSDB_NAMESPACE::Slice)> op,
         JNIEnv* env, jobject /*jobj*/, jbyteArray jkey, jint jkey_len) {
       jbyte* key = env->GetByteArrayElements(jkey, nullptr);
-      if(env->ExceptionCheck()) {
+      if (env->ExceptionCheck()) {
         // exception thrown: OutOfMemoryError
         return nullptr;
       }
@@ -2137,7 +2137,7 @@ class JniUtil {
 
       auto status = op(key_slice);
 
-      if(key != nullptr) {
+      if (key != nullptr) {
         env->ReleaseByteArrayElements(jkey, key, JNI_ABORT);
       }
 
@@ -2145,6 +2145,37 @@ class JniUtil {
           new ROCKSDB_NAMESPACE::Status(status));
     }
 
+    /*
+     * Helper for operations on a key which is a region of an array
+     * Used to extract the common code from seek/seekForPrev.
+     * Possible that it can be generalised from that.
+     *
+     * We use GetByteArrayRegion to copy the key region of the whole array into
+     * a char[] We suspect this is not much slower than GetByteArrayElements,
+     * which probably copies anyway.
+     */
+    static void k_op_region(std::function<void(ROCKSDB_NAMESPACE::Slice&)> op,
+                            JNIEnv* env, jbyteArray jkey, jint jkey_off,
+                            jint jkey_len) {
+      const std::unique_ptr<char[]> key(new char[jkey_len]);
+      if (key == nullptr) {
+        jclass oom_class = env->FindClass("/lang/java/OutOfMemoryError");
+        env->ThrowNew(oom_class,
+                      "Memory allocation failed in RocksDB JNI function");
+        return;
+      }
+      env->GetByteArrayRegion(jkey, jkey_off, jkey_len,
+                              reinterpret_cast<jbyte*>(key.get()));
+      if (env->ExceptionCheck()) {
+        // exception thrown: OutOfMemoryError
+        return;
+      }
+
+      ROCKSDB_NAMESPACE::Slice key_slice(reinterpret_cast<char*>(key.get()),
+                                         jkey_len);
+      op(key_slice);
+    }
+
     /*
      * Helper for operations on a value
      * for example WriteBatchWithIndex->GetFromBatch

java/rocksjni/sst_file_reader_iterator.cc

@@ -206,6 +206,29 @@ jint Java_org_rocksdb_SstFileReaderIterator_keyDirect0(
                                                   jtarget_off, jtarget_len);
 }
 
+/*
+ * This method supports fetching into indirect byte buffers;
+ * the Java wrapper extracts the byte[] and passes it here.
+ *
+ * Class:     org_rocksdb_SstFileReaderIterator
+ * Method:    keyByteArray0
+ * Signature: (J[BII)I
+ */
+jint Java_org_rocksdb_SstFileReaderIterator_keyByteArray0(
+    JNIEnv* env, jobject /*jobj*/, jlong handle, jbyteArray jkey, jint jkey_off,
+    jint jkey_len) {
+  auto* it = reinterpret_cast<ROCKSDB_NAMESPACE::Iterator*>(handle);
+  ROCKSDB_NAMESPACE::Slice key_slice = it->key();
+  auto slice_size = key_slice.size();
+  jsize copy_size = std::min(static_cast<uint32_t>(slice_size),
+                             static_cast<uint32_t>(jkey_len));
+  env->SetByteArrayRegion(
+      jkey, jkey_off, copy_size,
+      const_cast<jbyte*>(reinterpret_cast<const jbyte*>(key_slice.data())));
+
+  return static_cast<jsize>(slice_size);
+}
+
 /*
  * Class:     org_rocksdb_SstFileReaderIterator
  * Method:    valueDirect0
@@ -220,6 +243,29 @@ jint Java_org_rocksdb_SstFileReaderIterator_valueDirect0(
                                                   jtarget_off, jtarget_len);
 }
 
+/*
+ * This method supports fetching into indirect byte buffers;
+ * the Java wrapper extracts the byte[] and passes it here.
+ *
+ * Class:     org_rocksdb_SstFileReaderIterator
+ * Method:    valueByteArray0
+ * Signature: (J[BII)I
+ */
+jint Java_org_rocksdb_SstFileReaderIterator_valueByteArray0(
+    JNIEnv* env, jobject /*jobj*/, jlong handle, jbyteArray jvalue_target,
+    jint jvalue_off, jint jvalue_len) {
+  auto* it = reinterpret_cast<ROCKSDB_NAMESPACE::Iterator*>(handle);
+  ROCKSDB_NAMESPACE::Slice value_slice = it->value();
+  auto slice_size = value_slice.size();
+  jsize copy_size = std::min(static_cast<uint32_t>(slice_size),
+                             static_cast<uint32_t>(jvalue_len));
+  env->SetByteArrayRegion(
+      jvalue_target, jvalue_off, copy_size,
+      const_cast<jbyte*>(reinterpret_cast<const jbyte*>(value_slice.data())));
+
+  return static_cast<jsize>(slice_size);
+}
+
 /*
  * Class:     org_rocksdb_SstFileReaderIterator
  * Method:    seekDirect0
@@ -252,6 +298,60 @@ void Java_org_rocksdb_SstFileReaderIterator_seekForPrevDirect0(
                                           jtarget_len);
 }
 
+/*
+ * This method supports fetching into indirect byte buffers;
+ * the Java wrapper extracts the byte[] and passes it here.
+ *
+ * Class:     org_rocksdb_SstFileReaderIterator
+ * Method:    seekByteArray0
+ * Signature: (J[BII)V
+ */
+void Java_org_rocksdb_SstFileReaderIterator_seekByteArray0(
+    JNIEnv* env, jobject /*jobj*/, jlong handle, jbyteArray jtarget,
+    jint jtarget_off, jint jtarget_len) {
+  const std::unique_ptr<char[]> target(new char[jtarget_len]);
+  if (target == nullptr) {
+    jclass oom_class = env->FindClass("/lang/java/OutOfMemoryError");
+    env->ThrowNew(oom_class,
+                  "Memory allocation failed in RocksDB JNI function");
+    return;
+  }
+  env->GetByteArrayRegion(jtarget, jtarget_off, jtarget_len,
+                          reinterpret_cast<jbyte*>(target.get()));
+
+  ROCKSDB_NAMESPACE::Slice target_slice(target.get(), jtarget_len);
+
+  auto* it = reinterpret_cast<ROCKSDB_NAMESPACE::Iterator*>(handle);
+  it->Seek(target_slice);
+}
+
+/*
+ * This method supports fetching into indirect byte buffers;
+ * the Java wrapper extracts the byte[] and passes it here.
+ *
+ * Class:     org_rocksdb_SstFileReaderIterator
+ * Method:    seekForPrevByteArray0
+ * Signature: (J[BII)V
+ */
+void Java_org_rocksdb_SstFileReaderIterator_seekForPrevByteArray0(
+    JNIEnv* env, jobject /*jobj*/, jlong handle, jbyteArray jtarget,
+    jint jtarget_off, jint jtarget_len) {
+  const std::unique_ptr<char[]> target(new char[jtarget_len]);
+  if (target == nullptr) {
+    jclass oom_class = env->FindClass("/lang/java/OutOfMemoryError");
+    env->ThrowNew(oom_class,
+                  "Memory allocation failed in RocksDB JNI function");
+    return;
+  }
+  env->GetByteArrayRegion(jtarget, jtarget_off, jtarget_len,
+                          reinterpret_cast<jbyte*>(target.get()));
+
+  ROCKSDB_NAMESPACE::Slice target_slice(target.get(), jtarget_len);
+
+  auto* it = reinterpret_cast<ROCKSDB_NAMESPACE::Iterator*>(handle);
+  it->SeekForPrev(target_slice);
+}
+
 /*
  * Class:     org_rocksdb_SstFileReaderIterator
  * Method:    refresh0

java/rocksjni/write_batch_with_index.cc

@@ -765,6 +765,33 @@ void Java_org_rocksdb_WBWIRocksIterator_seekDirect0(
                                           jtarget_len);
 }
 
+/*
+ * This method supports fetching into indirect byte buffers;
+ * the Java wrapper extracts the byte[] and passes it here.
+ *
+ * Class:     org_rocksdb_WBWIRocksIterator
+ * Method:    seekByteArray0
+ * Signature: (J[BII)V
+ */
+void Java_org_rocksdb_WBWIRocksIterator_seekByteArray0(
+    JNIEnv* env, jobject /*jobj*/, jlong handle, jbyteArray jtarget,
+    jint jtarget_off, jint jtarget_len) {
+  const std::unique_ptr<char[]> target(new char[jtarget_len]);
+  if (target == nullptr) {
+    jclass oom_class = env->FindClass("/lang/java/OutOfMemoryError");
+    env->ThrowNew(oom_class,
+                  "Memory allocation failed in RocksDB JNI function");
+    return;
+  }
+  env->GetByteArrayRegion(jtarget, jtarget_off, jtarget_len,
+                          reinterpret_cast<jbyte*>(target.get()));
+
+  ROCKSDB_NAMESPACE::Slice target_slice(target.get(), jtarget_len);
+
+  auto* it = reinterpret_cast<ROCKSDB_NAMESPACE::WBWIIterator*>(handle);
+  it->Seek(target_slice);
+}
+
 /*
  * Class:     org_rocksdb_WBWIRocksIterator
  * Method:    seekForPrev0
@@ -790,6 +817,49 @@ void Java_org_rocksdb_WBWIRocksIterator_seekForPrev0(JNIEnv* env,
   env->ReleaseByteArrayElements(jtarget, target, JNI_ABORT);
 }
 
+/*
+ * Class:     org_rocksdb_WBWIRocksIterator
+ * Method:    seekForPrevDirect0
+ * Signature: (JLjava/nio/ByteBuffer;II)V
+ */
+void Java_org_rocksdb_WBWIRocksIterator_seekForPrevDirect0(
+    JNIEnv* env, jobject /*jobj*/, jlong handle, jobject jtarget,
+    jint jtarget_off, jint jtarget_len) {
+  auto* it = reinterpret_cast<ROCKSDB_NAMESPACE::WBWIIterator*>(handle);
+  auto seek_for_prev = [&it](ROCKSDB_NAMESPACE::Slice& target_slice) {
+    it->SeekForPrev(target_slice);
+  };
+  ROCKSDB_NAMESPACE::JniUtil::k_op_direct(seek_for_prev, env, jtarget,
+                                          jtarget_off, jtarget_len);
+}
+
+/*
+ * This method supports fetching into indirect byte buffers;
+ * the Java wrapper extracts the byte[] and passes it here.
+ *
+ * Class:     org_rocksdb_WBWIRocksIterator
+ * Method:    seekForPrevByteArray0
+ * Signature: (J[BII)V
+ */
+void Java_org_rocksdb_WBWIRocksIterator_seekForPrevByteArray0(
+    JNIEnv* env, jobject /*jobj*/, jlong handle, jbyteArray jtarget,
+    jint jtarget_off, jint jtarget_len) {
+  const std::unique_ptr<char[]> target(new char[jtarget_len]);
+  if (target == nullptr) {
+    jclass oom_class = env->FindClass("/lang/java/OutOfMemoryError");
+    env->ThrowNew(oom_class,
+                  "Memory allocation failed in RocksDB JNI function");
+    return;
+  }
+  env->GetByteArrayRegion(jtarget, jtarget_off, jtarget_len,
+                          reinterpret_cast<jbyte*>(target.get()));
+
+  ROCKSDB_NAMESPACE::Slice target_slice(target.get(), jtarget_len);
+
+  auto* it = reinterpret_cast<ROCKSDB_NAMESPACE::WBWIIterator*>(handle);
+  it->SeekForPrev(target_slice);
+}
+
 /*
  * Class:     org_rocksdb_WBWIRocksIterator
  * Method:    status0

java/src/main/java/org/rocksdb/AbstractRocksIterator.java

@@ -55,30 +55,40 @@ public abstract class AbstractRocksIterator<P extends RocksObject>
   }
 
   @Override
-  public void seek(byte[] target) {
+  public void seek(final byte[] target) {
     assert (isOwningHandle());
     seek0(nativeHandle_, target, target.length);
   }
 
- @Override
+  @Override
- public void seekForPrev(byte[] target) {
+  public void seekForPrev(final byte[] target) {
-   assert (isOwningHandle());
+    assert (isOwningHandle());
-   seekForPrev0(nativeHandle_, target, target.length);
+    seekForPrev0(nativeHandle_, target, target.length);
- }
+  }
 
- @Override
+  @Override
- public void seek(ByteBuffer target) {
+  public void seek(final ByteBuffer target) {
-   assert (isOwningHandle() && target.isDirect());
+    assert (isOwningHandle());
-   seekDirect0(nativeHandle_, target, target.position(), target.remaining());
+    if (target.isDirect()) {
-   target.position(target.limit());
+      seekDirect0(nativeHandle_, target, target.position(), target.remaining());
- }
+    } else {
+      seekByteArray0(nativeHandle_, target.array(), target.arrayOffset() + target.position(),
+          target.remaining());
+    }
+    target.position(target.limit());
+  }
 
- @Override
+  @Override
- public void seekForPrev(ByteBuffer target) {
+  public void seekForPrev(final ByteBuffer target) {
-   assert (isOwningHandle() && target.isDirect());
+    assert (isOwningHandle());
-   seekForPrevDirect0(nativeHandle_, target, target.position(), target.remaining());
+    if (target.isDirect()) {
-   target.position(target.limit());
+      seekForPrevDirect0(nativeHandle_, target, target.position(), target.remaining());
- }
+    } else {
+      seekForPrevByteArray0(nativeHandle_, target.array(), target.arrayOffset() + target.position(),
+          target.remaining());
+    }
+    target.position(target.limit());
+  }
 
   @Override
   public void next() {
@@ -129,5 +139,8 @@ public abstract class AbstractRocksIterator<P extends RocksObject>
   abstract void seekForPrev0(long handle, byte[] target, int targetLen);
   abstract void seekDirect0(long handle, ByteBuffer target, int targetOffset, int targetLen);
   abstract void seekForPrevDirect0(long handle, ByteBuffer target, int targetOffset, int targetLen);
+  abstract void seekByteArray0(long handle, byte[] target, int targetOffset, int targetLen);
+  abstract void seekForPrevByteArray0(long handle, byte[] target, int targetOffset, int targetLen);
+
   abstract void status0(long handle) throws RocksDBException;
 }

java/src/main/java/org/rocksdb/RocksIterator.java

@@ -21,7 +21,7 @@ import java.nio.ByteBuffer;
  * @see org.rocksdb.RocksObject
  */
 public class RocksIterator extends AbstractRocksIterator<RocksDB> {
-  protected RocksIterator(RocksDB rocksDB, long nativeHandle) {
+  protected RocksIterator(final RocksDB rocksDB, final long nativeHandle) {
     super(rocksDB, nativeHandle);
   }
 
@@ -54,9 +54,16 @@ public class RocksIterator extends AbstractRocksIterator<RocksDB> {
    *     input buffer {@code key} is insufficient and partial result will
    *     be returned.
    */
-  public int key(ByteBuffer key) {
+  public int key(final ByteBuffer key) {
-    assert (isOwningHandle() && key.isDirect());
+    assert isOwningHandle();
-    int result = keyDirect0(nativeHandle_, key, key.position(), key.remaining());
+    final int result;
+    if (key.isDirect()) {
+      result = keyDirect0(nativeHandle_, key, key.position(), key.remaining());
+    } else {
+      assert key.hasArray();
+      result = keyByteArray0(
+          nativeHandle_, key.array(), key.arrayOffset() + key.position(), key.remaining());
+    }
     key.limit(Math.min(key.position() + result, key.limit()));
     return result;
   }
@@ -89,9 +96,16 @@ public class RocksIterator extends AbstractRocksIterator<RocksDB> {
    *     input buffer {@code value} is insufficient and partial result will
    *     be returned.
    */
-  public int value(ByteBuffer value) {
+  public int value(final ByteBuffer value) {
-    assert (isOwningHandle() && value.isDirect());
+    assert isOwningHandle();
-    int result = valueDirect0(nativeHandle_, value, value.position(), value.remaining());
+    final int result;
+    if (value.isDirect()) {
+      result = valueDirect0(nativeHandle_, value, value.position(), value.remaining());
+    } else {
+      assert value.hasArray();
+      result = valueByteArray0(
+          nativeHandle_, value.array(), value.arrayOffset() + value.position(), value.remaining());
+    }
     value.limit(Math.min(value.position() + result, value.limit()));
     return result;
   }
@@ -108,12 +122,19 @@ public class RocksIterator extends AbstractRocksIterator<RocksDB> {
   @Override
   final native void seekDirect0(long handle, ByteBuffer target, int targetOffset, int targetLen);
   @Override
+  final native void seekByteArray0(long handle, byte[] target, int targetOffset, int targetLen);
+  @Override
   final native void seekForPrevDirect0(
       long handle, ByteBuffer target, int targetOffset, int targetLen);
+  @Override
+  final native void seekForPrevByteArray0(
+      long handle, byte[] target, int targetOffset, int targetLen);
   @Override final native void status0(long handle) throws RocksDBException;
 
   private native byte[] key0(long handle);
   private native byte[] value0(long handle);
   private native int keyDirect0(long handle, ByteBuffer buffer, int bufferOffset, int bufferLen);
+  private native int keyByteArray0(long handle, byte[] array, int arrayOffset, int arrayLen);
   private native int valueDirect0(long handle, ByteBuffer buffer, int bufferOffset, int bufferLen);
+  private native int valueByteArray0(long handle, byte[] array, int arrayOffset, int arrayLen);
 }

java/src/main/java/org/rocksdb/SstFileReaderIterator.java

@@ -21,7 +21,7 @@ import java.nio.ByteBuffer;
  * @see RocksObject
  */
 public class SstFileReaderIterator extends AbstractRocksIterator<SstFileReader> {
-  protected SstFileReaderIterator(SstFileReader reader, long nativeHandle) {
+  protected SstFileReaderIterator(final SstFileReader reader, final long nativeHandle) {
     super(reader, nativeHandle);
   }
 
@@ -54,9 +54,15 @@ public class SstFileReaderIterator extends AbstractRocksIterator<SstFileReader>
    *     input buffer {@code key} is insufficient and partial result will
    *     be returned.
    */
-  public int key(ByteBuffer key) {
+  public int key(final ByteBuffer key) {
-    assert (isOwningHandle() && key.isDirect());
+    assert (isOwningHandle());
-    int result = keyDirect0(nativeHandle_, key, key.position(), key.remaining());
+    final int result;
+    if (key.isDirect()) {
+      result = keyDirect0(nativeHandle_, key, key.position(), key.remaining());
+    } else {
+      result = keyByteArray0(
+          nativeHandle_, key.array(), key.arrayOffset() + key.position(), key.remaining());
+    }
     key.limit(Math.min(key.position() + result, key.limit()));
     return result;
   }
@@ -89,9 +95,15 @@ public class SstFileReaderIterator extends AbstractRocksIterator<SstFileReader>
    *     input buffer {@code value} is insufficient and partial result will
    *     be returned.
    */
-  public int value(ByteBuffer value) {
+  public int value(final ByteBuffer value) {
-    assert (isOwningHandle() && value.isDirect());
+    assert (isOwningHandle());
-    int result = valueDirect0(nativeHandle_, value, value.position(), value.remaining());
+    final int result;
+    if (value.isDirect()) {
+      result = valueDirect0(nativeHandle_, value, value.position(), value.remaining());
+    } else {
+      result = valueByteArray0(
+          nativeHandle_, value.array(), value.arrayOffset() + value.position(), value.remaining());
+    }
     value.limit(Math.min(value.position() + result, value.limit()));
     return result;
   }
@@ -106,16 +118,23 @@ public class SstFileReaderIterator extends AbstractRocksIterator<SstFileReader>
   @Override final native void seek0(long handle, byte[] target, int targetLen);
   @Override final native void seekForPrev0(long handle, byte[] target, int targetLen);
   @Override final native void status0(long handle) throws RocksDBException;
-
-  private native byte[] key0(long handle);
-  private native byte[] value0(long handle);
-
-  private native int keyDirect0(long handle, ByteBuffer buffer, int bufferOffset, int bufferLen);
-  private native int valueDirect0(long handle, ByteBuffer buffer, int bufferOffset, int bufferLen);
-
   @Override
   final native void seekDirect0(long handle, ByteBuffer target, int targetOffset, int targetLen);
   @Override
   final native void seekForPrevDirect0(
       long handle, ByteBuffer target, int targetOffset, int targetLen);
+  @Override
+  final native void seekByteArray0(
+      final long handle, final byte[] target, final int targetOffset, final int targetLen);
+  @Override
+  final native void seekForPrevByteArray0(
+      final long handle, final byte[] target, final int targetOffset, final int targetLen);
+
+  private native byte[] key0(long handle);
+  private native byte[] value0(long handle);
+
+  private native int keyDirect0(long handle, ByteBuffer buffer, int bufferOffset, int bufferLen);
+  private native int keyByteArray0(long handle, byte[] buffer, int bufferOffset, int bufferLen);
+  private native int valueDirect0(long handle, ByteBuffer buffer, int bufferOffset, int bufferLen);
+  private native int valueByteArray0(long handle, byte[] buffer, int bufferOffset, int bufferLen);
 }

java/src/main/java/org/rocksdb/WBWIRocksIterator.java

@@ -31,7 +31,7 @@ public class WBWIRocksIterator
    */
   public WriteEntry entry() {
     assert(isOwningHandle());
-    final long ptrs[] = entry1(nativeHandle_);
+    final long[] ptrs = entry1(nativeHandle_);
 
     entry.type = WriteType.fromId((byte)ptrs[0]);
     entry.key.resetNativeHandle(ptrs[1], ptrs[1] != 0);
@@ -51,7 +51,17 @@ public class WBWIRocksIterator
   @Override final native void seekForPrev0(long handle, byte[] target, int targetLen);
   @Override final native void status0(long handle) throws RocksDBException;
   @Override
-  final native void seekDirect0(long handle, ByteBuffer target, int targetOffset, int targetLen);
+  final native void seekDirect0(
+      final long handle, final ByteBuffer target, final int targetOffset, final int targetLen);
+  @Override
+  final native void seekForPrevDirect0(
+      final long handle, final ByteBuffer target, final int targetOffset, final int targetLen);
+  @Override
+  final native void seekByteArray0(
+      final long handle, final byte[] target, final int targetOffset, final int targetLen);
+  @Override
+  final native void seekForPrevByteArray0(
+      final long handle, final byte[] target, final int targetOffset, final int targetLen);
 
   private native long[] entry1(final long handle);
 
@@ -190,9 +200,4 @@ public class WBWIRocksIterator
       key.close();
     }
   }
-
-  @Override
-  void seekForPrevDirect0(long handle, ByteBuffer target, int targetOffset, int targetLen) {
-    throw new IllegalAccessError("Not implemented");
-  }
 }

java/src/test/java/org/rocksdb/RocksIteratorTest.java

@@ -7,6 +7,7 @@ package org.rocksdb;
 import static org.assertj.core.api.Assertions.assertThat;
 
 import java.nio.ByteBuffer;
+import java.nio.charset.StandardCharsets;
 import org.junit.ClassRule;
 import org.junit.Rule;
 import org.junit.Test;
@@ -21,13 +22,33 @@ public class RocksIteratorTest {
   @Rule
   public TemporaryFolder dbFolder = new TemporaryFolder();
 
+  private void validateByteBufferResult(
+      final int fetched, final ByteBuffer byteBuffer, final String expected) {
+    assertThat(fetched).isEqualTo(expected.length());
+    assertThat(byteBuffer.position()).isEqualTo(0);
+    assertThat(byteBuffer.limit()).isEqualTo(Math.min(byteBuffer.remaining(), expected.length()));
+    final int bufferSpace = byteBuffer.remaining();
+    final byte[] contents = new byte[bufferSpace];
+    byteBuffer.get(contents, 0, bufferSpace);
+    assertThat(contents).isEqualTo(
+        expected.substring(0, bufferSpace).getBytes(StandardCharsets.UTF_8));
+  }
+
+  private void validateKey(
+      final RocksIterator iterator, final ByteBuffer byteBuffer, final String key) {
+    validateByteBufferResult(iterator.key(byteBuffer), byteBuffer, key);
+  }
+
+  private void validateValue(
+      final RocksIterator iterator, final ByteBuffer byteBuffer, final String value) {
+    validateByteBufferResult(iterator.value(byteBuffer), byteBuffer, value);
+  }
+
   @Test
   public void rocksIterator() throws RocksDBException {
-    try (final Options options = new Options()
+    try (final Options options =
-        .setCreateIfMissing(true)
+             new Options().setCreateIfMissing(true).setCreateMissingColumnFamilies(true);
-        .setCreateMissingColumnFamilies(true);
+         final RocksDB db = RocksDB.open(options, dbFolder.getRoot().getAbsolutePath())) {
-         final RocksDB db = RocksDB.open(options,
-             dbFolder.getRoot().getAbsolutePath())) {
       db.put("key1".getBytes(), "value1".getBytes());
       db.put("key2".getBytes(), "value2".getBytes());
 
@@ -37,37 +58,20 @@ public class RocksIteratorTest {
         assertThat(iterator.key()).isEqualTo("key1".getBytes());
         assertThat(iterator.value()).isEqualTo("value1".getBytes());
 
-        ByteBuffer key = ByteBuffer.allocateDirect(2);
+        validateKey(iterator, ByteBuffer.allocateDirect(2), "key1");
-        ByteBuffer value = ByteBuffer.allocateDirect(2);
+        validateKey(iterator, ByteBuffer.allocateDirect(2), "key0");
-        assertThat(iterator.key(key)).isEqualTo(4);
+        validateKey(iterator, ByteBuffer.allocateDirect(4), "key1");
-        assertThat(iterator.value(value)).isEqualTo(6);
+        validateKey(iterator, ByteBuffer.allocateDirect(5), "key1");
+        validateValue(iterator, ByteBuffer.allocateDirect(2), "value2");
+        validateValue(iterator, ByteBuffer.allocateDirect(2), "vasicu");
+        validateValue(iterator, ByteBuffer.allocateDirect(8), "value1");
 
-        assertThat(key.position()).isEqualTo(0);
+        validateKey(iterator, ByteBuffer.allocate(2), "key1");
-        assertThat(key.limit()).isEqualTo(2);
+        validateKey(iterator, ByteBuffer.allocate(2), "key0");
-        assertThat(value.position()).isEqualTo(0);
+        validateKey(iterator, ByteBuffer.allocate(4), "key1");
-        assertThat(value.limit()).isEqualTo(2);
+        validateKey(iterator, ByteBuffer.allocate(5), "key1");
-
+        validateValue(iterator, ByteBuffer.allocate(2), "value1");
-        byte[] tmp = new byte[2];
+        validateValue(iterator, ByteBuffer.allocate(8), "value1");
-        key.get(tmp);
-        assertThat(tmp).isEqualTo("ke".getBytes());
-        value.get(tmp);
-        assertThat(tmp).isEqualTo("va".getBytes());
-
-        key = ByteBuffer.allocateDirect(12);
-        value = ByteBuffer.allocateDirect(12);
-        assertThat(iterator.key(key)).isEqualTo(4);
-        assertThat(iterator.value(value)).isEqualTo(6);
-        assertThat(key.position()).isEqualTo(0);
-        assertThat(key.limit()).isEqualTo(4);
-        assertThat(value.position()).isEqualTo(0);
-        assertThat(value.limit()).isEqualTo(6);
-
-        tmp = new byte[4];
-        key.get(tmp);
-        assertThat(tmp).isEqualTo("key1".getBytes());
-        tmp = new byte[6];
-        value.get(tmp);
-        assertThat(tmp).isEqualTo("value1".getBytes());
 
         iterator.next();
         assertThat(iterator.isValid()).isTrue();
@@ -87,24 +91,85 @@ public class RocksIteratorTest {
         assertThat(iterator.value()).isEqualTo("value2".getBytes());
         iterator.status();
 
-        key.clear();
+        {
-        key.put("key1".getBytes());
+          final ByteBuffer key = ByteBuffer.allocate(12);
-        key.flip();
+          key.put("key1".getBytes()).flip();
-        iterator.seek(key);
+          iterator.seek(key);
-        assertThat(iterator.isValid()).isTrue();
+          assertThat(iterator.isValid()).isTrue();
-        assertThat(iterator.value()).isEqualTo("value1".getBytes());
+          assertThat(iterator.value()).isEqualTo("value1".getBytes());
-        assertThat(key.position()).isEqualTo(4);
+          assertThat(key.position()).isEqualTo(4);
-        assertThat(key.limit()).isEqualTo(4);
+          assertThat(key.limit()).isEqualTo(4);
 
-        key.clear();
+          validateValue(iterator, ByteBuffer.allocateDirect(12), "value1");
-        key.put("key2".getBytes());
+          validateValue(iterator, ByteBuffer.allocateDirect(4), "valu56");
-        key.flip();
+        }
-        iterator.seekForPrev(key);
+
-        assertThat(iterator.isValid()).isTrue();
+        {
-        assertThat(iterator.value()).isEqualTo("value2".getBytes());
+          final ByteBuffer key = ByteBuffer.allocate(12);
-        assertThat(key.position()).isEqualTo(4);
+          key.put("key2".getBytes()).flip();
-        assertThat(key.limit()).isEqualTo(4);
+          iterator.seekForPrev(key);
+          assertThat(iterator.isValid()).isTrue();
+          assertThat(iterator.value()).isEqualTo("value2".getBytes());
+          assertThat(key.position()).isEqualTo(4);
+          assertThat(key.limit()).isEqualTo(4);
+        }
+
+        {
+          final ByteBuffer key = ByteBuffer.allocate(12);
+          key.put("key1".getBytes()).flip();
+          iterator.seek(key);
+          assertThat(iterator.isValid()).isTrue();
+          assertThat(iterator.value()).isEqualTo("value1".getBytes());
+          assertThat(key.position()).isEqualTo(4);
+          assertThat(key.limit()).isEqualTo(4);
+        }
+
+        {
+          // Check offsets of slice byte buffers
+          final ByteBuffer key0 = ByteBuffer.allocate(24);
+          key0.put("key2key2".getBytes());
+          final ByteBuffer key = key0.slice();
+          key.put("key1".getBytes()).flip();
+          iterator.seek(key);
+          assertThat(iterator.isValid()).isTrue();
+          assertThat(iterator.value()).isEqualTo("value1".getBytes());
+          assertThat(key.position()).isEqualTo(4);
+          assertThat(key.limit()).isEqualTo(4);
+        }
+
+        {
+          // Check offsets of slice byte buffers
+          final ByteBuffer key0 = ByteBuffer.allocateDirect(24);
+          key0.put("key2key2".getBytes());
+          final ByteBuffer key = key0.slice();
+          key.put("key1".getBytes()).flip();
+          iterator.seek(key);
+          assertThat(iterator.isValid()).isTrue();
+          assertThat(iterator.value()).isEqualTo("value1".getBytes());
+          assertThat(key.position()).isEqualTo(4);
+          assertThat(key.limit()).isEqualTo(4);
+        }
+
+        {
+          final ByteBuffer key = ByteBuffer.allocate(12);
+          key.put("key2".getBytes()).flip();
+          iterator.seekForPrev(key);
+          assertThat(iterator.isValid()).isTrue();
+          assertThat(iterator.value()).isEqualTo("value2".getBytes());
+          assertThat(key.position()).isEqualTo(4);
+          assertThat(key.limit()).isEqualTo(4);
+        }
       }
+    }
+  }
+
+  @Test
+  public void rocksIteratorSeekAndInsert() throws RocksDBException {
+    try (final Options options =
+             new Options().setCreateIfMissing(true).setCreateMissingColumnFamilies(true);
+         final RocksDB db = RocksDB.open(options, dbFolder.getRoot().getAbsolutePath())) {
+      db.put("key1".getBytes(), "value1".getBytes());
+      db.put("key2".getBytes(), "value2".getBytes());
 
       try (final RocksIterator iterator = db.newIterator()) {
         iterator.seek("key0".getBytes());
@@ -192,8 +257,8 @@ public class RocksIteratorTest {
       }
 
       // Test case: release iterator after custom CF close
-      ColumnFamilyDescriptor cfd1 = new ColumnFamilyDescriptor("cf1".getBytes());
+      final ColumnFamilyDescriptor cfd1 = new ColumnFamilyDescriptor("cf1".getBytes());
-      ColumnFamilyHandle cfHandle1 = db.createColumnFamily(cfd1);
+      final ColumnFamilyHandle cfHandle1 = db.createColumnFamily(cfd1);
       db.put(cfHandle1, "key1".getBytes(), "value1".getBytes());
 
       try (final RocksIterator iterator = db.newIterator(cfHandle1)) {
@@ -206,8 +271,8 @@ public class RocksIteratorTest {
       }
 
       // Test case: release iterator after custom CF drop & close
-      ColumnFamilyDescriptor cfd2 = new ColumnFamilyDescriptor("cf2".getBytes());
+      final ColumnFamilyDescriptor cfd2 = new ColumnFamilyDescriptor("cf2".getBytes());
-      ColumnFamilyHandle cfHandle2 = db.createColumnFamily(cfd2);
+      final ColumnFamilyHandle cfHandle2 = db.createColumnFamily(cfd2);
       db.put(cfHandle2, "key2".getBytes(), "value2".getBytes());
 
       try (final RocksIterator iterator = db.newIterator(cfHandle2)) {

java/src/test/java/org/rocksdb/SstFileReaderTest.java

@@ -13,17 +13,21 @@ import java.io.File;
 import java.io.IOException;
 import java.nio.ByteBuffer;
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
-import org.rocksdb.util.BytewiseComparator;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+import org.rocksdb.util.ByteBufferAllocator;
 
+@RunWith(Parameterized.class)
 public class SstFileReaderTest {
   private static final String SST_FILE_NAME = "test.sst";
 
-  class KeyValueWithOp {
+  static class KeyValueWithOp {
-    KeyValueWithOp(String key, String value, OpType opType) {
+    KeyValueWithOp(final String key, final String value, final OpType opType) {
       this.key = key;
       this.value = value;
       this.opType = opType;
@@ -41,13 +45,23 @@ public class SstFileReaderTest {
       return opType;
     }
 
-    private String key;
+    private final String key;
-    private String value;
+    private final String value;
-    private OpType opType;
+    private final OpType opType;
   }
 
   @Rule public TemporaryFolder parentFolder = new TemporaryFolder();
 
+  @Parameterized.Parameters(name = "{0}")
+  public static Iterable<Object[]> parameters() {
+    return Arrays.asList(new Object[][] {
+        {"direct", ByteBufferAllocator.DIRECT}, {"indirect", ByteBufferAllocator.HEAP}});
+  }
+
+  @Parameterized.Parameter(0) public String name;
+
+  @Parameterized.Parameter(1) public ByteBufferAllocator byteBufferAllocator;
+
   enum OpType { PUT, PUT_BYTES, MERGE, MERGE_BYTES, DELETE, DELETE_BYTES }
 
   private File newSstFile(final List<KeyValueWithOp> keyValues)
@@ -55,17 +69,17 @@ public class SstFileReaderTest {
     final EnvOptions envOptions = new EnvOptions();
     final StringAppendOperator stringAppendOperator = new StringAppendOperator();
     final Options options = new Options().setMergeOperator(stringAppendOperator);
-    SstFileWriter sstFileWriter;
+    final SstFileWriter sstFileWriter;
     sstFileWriter = new SstFileWriter(envOptions, options);
 
     final File sstFile = parentFolder.newFile(SST_FILE_NAME);
     try {
       sstFileWriter.open(sstFile.getAbsolutePath());
-      for (KeyValueWithOp keyValue : keyValues) {
+      for (final KeyValueWithOp keyValue : keyValues) {
-        Slice keySlice = new Slice(keyValue.getKey());
+        final Slice keySlice = new Slice(keyValue.getKey());
-        Slice valueSlice = new Slice(keyValue.getValue());
+        final Slice valueSlice = new Slice(keyValue.getValue());
-        byte[] keyBytes = keyValue.getKey().getBytes();
+        final byte[] keyBytes = keyValue.getKey().getBytes();
-        byte[] valueBytes = keyValue.getValue().getBytes();
+        final byte[] valueBytes = keyValue.getValue().getBytes();
         switch (keyValue.getOpType()) {
           case PUT:
             sstFileWriter.put(keySlice, valueSlice);
@@ -105,6 +119,8 @@ public class SstFileReaderTest {
   public void readSstFile() throws RocksDBException, IOException {
     final List<KeyValueWithOp> keyValues = new ArrayList<>();
     keyValues.add(new KeyValueWithOp("key1", "value1", OpType.PUT));
+    keyValues.add(new KeyValueWithOp("key2", "value2", OpType.PUT));
+    keyValues.add(new KeyValueWithOp("key3", "value3", OpType.PUT));
 
     final File sstFile = newSstFile(keyValues);
     try (final StringAppendOperator stringAppendOperator = new StringAppendOperator();
@@ -123,33 +139,84 @@ public class SstFileReaderTest {
       reader.verifyChecksum();
 
       // Verify Table Properties
-      assertEquals(reader.getTableProperties().getNumEntries(), 1);
+      assertEquals(reader.getTableProperties().getNumEntries(), 3);
 
       // Check key and value
       assertThat(iterator.key()).isEqualTo("key1".getBytes());
       assertThat(iterator.value()).isEqualTo("value1".getBytes());
 
-      ByteBuffer direct = ByteBuffer.allocateDirect(128);
+      final ByteBuffer byteBuffer = byteBufferAllocator.allocate(128);
-      direct.put("key1".getBytes()).flip();
+      byteBuffer.put("key1".getBytes()).flip();
-      iterator.seek(direct);
+      iterator.seek(byteBuffer);
-      assertThat(direct.position()).isEqualTo(4);
+      assertThat(byteBuffer.position()).isEqualTo(4);
-      assertThat(direct.limit()).isEqualTo(4);
+      assertThat(byteBuffer.limit()).isEqualTo(4);
 
       assertThat(iterator.isValid()).isTrue();
       assertThat(iterator.key()).isEqualTo("key1".getBytes());
       assertThat(iterator.value()).isEqualTo("value1".getBytes());
 
-      direct.clear();
+      {
-      assertThat(iterator.key(direct)).isEqualTo("key1".getBytes().length);
+        byteBuffer.clear();
-      byte[] dst = new byte["key1".getBytes().length];
+        assertThat(iterator.key(byteBuffer)).isEqualTo("key1".getBytes().length);
-      direct.get(dst);
+        final byte[] dst = new byte["key1".getBytes().length];
-      assertThat(new String(dst)).isEqualTo("key1");
+        byteBuffer.get(dst);
+        assertThat(new String(dst)).isEqualTo("key1");
+      }
 
-      direct.clear();
+      {
-      assertThat(iterator.value(direct)).isEqualTo("value1".getBytes().length);
+        byteBuffer.clear();
-      dst = new byte["value1".getBytes().length];
+        byteBuffer.put("PREFIX".getBytes());
-      direct.get(dst);
+        final ByteBuffer slice = byteBuffer.slice();
-      assertThat(new String(dst)).isEqualTo("value1");
+        assertThat(iterator.key(byteBuffer)).isEqualTo("key1".getBytes().length);
+        final byte[] dst = new byte["key1".getBytes().length];
+        slice.get(dst);
+        assertThat(new String(dst)).isEqualTo("key1");
+      }
+
+      {
+        byteBuffer.clear();
+        assertThat(iterator.value(byteBuffer)).isEqualTo("value1".getBytes().length);
+        final byte[] dst = new byte["value1".getBytes().length];
+        byteBuffer.get(dst);
+        assertThat(new String(dst)).isEqualTo("value1");
+      }
+
+      byteBuffer.clear();
+      byteBuffer.put("key1point5".getBytes()).flip();
+      iterator.seek(byteBuffer);
+      assertThat(iterator.isValid()).isTrue();
+      assertThat(iterator.key()).isEqualTo("key2".getBytes());
+      assertThat(iterator.value()).isEqualTo("value2".getBytes());
+
+      byteBuffer.clear();
+      byteBuffer.put("key1point5".getBytes()).flip();
+      iterator.seekForPrev(byteBuffer);
+      assertThat(iterator.isValid()).isTrue();
+      assertThat(iterator.key()).isEqualTo("key1".getBytes());
+      assertThat(iterator.value()).isEqualTo("value1".getBytes());
+
+      byteBuffer.clear();
+      byteBuffer.put("key2point5".getBytes()).flip();
+      iterator.seek(byteBuffer);
+      assertThat(iterator.isValid()).isTrue();
+      assertThat(iterator.key()).isEqualTo("key3".getBytes());
+      assertThat(iterator.value()).isEqualTo("value3".getBytes());
+
+      byteBuffer.clear();
+      byteBuffer.put("key2point5".getBytes()).flip();
+      iterator.seekForPrev(byteBuffer);
+      assertThat(iterator.isValid()).isTrue();
+      assertThat(iterator.key()).isEqualTo("key2".getBytes());
+      assertThat(iterator.value()).isEqualTo("value2".getBytes());
+
+      byteBuffer.clear();
+      byteBuffer.put("PREFIX".getBytes());
+      final ByteBuffer slice = byteBuffer.slice();
+      slice.put("key1point5".getBytes()).flip();
+      iterator.seekForPrev(slice);
+      assertThat(iterator.isValid()).isTrue();
+      assertThat(iterator.key()).isEqualTo("key1".getBytes());
+      assertThat(iterator.value()).isEqualTo("value1".getBytes());
     }
   }
 }

java/src/test/java/org/rocksdb/WriteBatchWithIndexTest.java

@@ -20,6 +20,7 @@ import org.junit.ClassRule;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
+import org.rocksdb.util.ByteBufferAllocator;
 
 public class WriteBatchWithIndexTest {
 
@@ -192,6 +193,236 @@ public class WriteBatchWithIndexTest {
     }
   }
 
+  @Test
+  public void readYourOwnWritesCfIterDirectBB() throws RocksDBException {
+    readYourOwnWritesCfIterDirect(ByteBufferAllocator.DIRECT);
+  }
+
+  @Test
+  public void readYourOwnWritesCfIterIndirectBB() throws RocksDBException {
+    readYourOwnWritesCfIterDirect(ByteBufferAllocator.HEAP);
+  }
+
+  public void readYourOwnWritesCfIterDirect(final ByteBufferAllocator byteBufferAllocator)
+      throws RocksDBException {
+    final List<ColumnFamilyDescriptor> cfNames =
+        Arrays.asList(new ColumnFamilyDescriptor(RocksDB.DEFAULT_COLUMN_FAMILY),
+            new ColumnFamilyDescriptor("new_cf".getBytes()));
+
+    final List<ColumnFamilyHandle> columnFamilyHandleList = new ArrayList<>();
+
+    // Test open database with column family names
+    try (final DBOptions options =
+             new DBOptions().setCreateIfMissing(true).setCreateMissingColumnFamilies(true);
+         final RocksDB db = RocksDB.open(
+             options, dbFolder.getRoot().getAbsolutePath(), cfNames, columnFamilyHandleList)) {
+      final ColumnFamilyHandle newCf = columnFamilyHandleList.get(1);
+
+      try {
+        final byte[] kv1 = "key1".getBytes();
+        final byte[] vv1 = "value1".getBytes();
+        final ByteBuffer k1 = byteBufferAllocator.allocate(12);
+        k1.put(kv1);
+        final byte[] kv2 = "key2".getBytes();
+        final byte[] vv2 = "value2".getBytes();
+        final ByteBuffer k2 = byteBufferAllocator.allocate(12);
+        k2.put(kv2);
+
+        db.put(newCf, kv1, vv1);
+        db.put(newCf, kv2, vv2);
+
+        try (final WriteBatchWithIndex wbwi = new WriteBatchWithIndex(true);
+             final ReadOptions readOptions = new ReadOptions();
+             final RocksIterator base = db.newIterator(newCf, readOptions);
+             final RocksIterator it = wbwi.newIteratorWithBase(newCf, base, readOptions)) {
+          k1.flip();
+          it.seek(k1);
+          assertThat(it.isValid()).isTrue();
+          assertThat(it.key()).isEqualTo(kv1);
+          assertThat(it.value()).isEqualTo(vv1);
+
+          k2.flip();
+          it.seek(k2);
+          assertThat(it.isValid()).isTrue();
+          assertThat(it.key()).isEqualTo(kv2);
+          assertThat(it.value()).isEqualTo(vv2);
+
+          final byte[] kv1point5 = "key1point5".getBytes();
+          final ByteBuffer k1point5 = byteBufferAllocator.allocate(12);
+          k1point5.put(kv1point5);
+
+          k1point5.flip();
+          it.seek(k1point5);
+          assertThat(it.isValid()).isTrue();
+          assertThat(it.key()).isEqualTo(kv2);
+          assertThat(it.value()).isEqualTo(vv2);
+
+          k1point5.flip();
+          it.seekForPrev(k1point5);
+          assertThat(it.isValid()).isTrue();
+          assertThat(it.key()).isEqualTo(kv1);
+          assertThat(it.value()).isEqualTo(vv1);
+
+          // put data to the write batch and make sure we can read it.
+          final byte[] kv3 = "key3".getBytes();
+          final ByteBuffer k3 = byteBufferAllocator.allocate(12);
+          k3.put(kv3);
+          final byte[] vv3 = "value3".getBytes();
+          wbwi.put(newCf, kv3, vv3);
+          k3.flip();
+          it.seek(k3);
+          assertThat(it.isValid()).isTrue();
+          assertThat(it.key()).isEqualTo(kv3);
+          assertThat(it.value()).isEqualTo(vv3);
+
+          // update k2 in the write batch and check the value
+          final byte[] v2Other = "otherValue2".getBytes();
+          wbwi.put(newCf, kv2, v2Other);
+          k2.flip();
+          it.seek(k2);
+          assertThat(it.isValid()).isTrue();
+          assertThat(it.key()).isEqualTo(kv2);
+          assertThat(it.value()).isEqualTo(v2Other);
+
+          // delete k1 and make sure we can read back the write
+          wbwi.delete(newCf, kv1);
+          k1.flip();
+          it.seek(k1);
+          assertThat(it.key()).isNotEqualTo(kv1);
+
+          // reinsert k1 and make sure we see the new value
+          final byte[] v1Other = "otherValue1".getBytes();
+          wbwi.put(newCf, kv1, v1Other);
+          k1.flip();
+          it.seek(k1);
+          assertThat(it.isValid()).isTrue();
+          assertThat(it.key()).isEqualTo(kv1);
+          assertThat(it.value()).isEqualTo(v1Other);
+
+          // single remove k3 and make sure we can read back the write
+          wbwi.singleDelete(newCf, kv3);
+          k3.flip();
+          it.seek(k3);
+          assertThat(it.isValid()).isEqualTo(false);
+
+          // reinsert k3 and make sure we see the new value
+          final byte[] v3Other = "otherValue3".getBytes();
+          wbwi.put(newCf, kv3, v3Other);
+          k3.flip();
+          it.seek(k3);
+          assertThat(it.isValid()).isTrue();
+          assertThat(it.key()).isEqualTo(kv3);
+          assertThat(it.value()).isEqualTo(v3Other);
+        }
+      } finally {
+        for (final ColumnFamilyHandle columnFamilyHandle : columnFamilyHandleList) {
+          columnFamilyHandle.close();
+        }
+      }
+    }
+  }
+
+  @Test
+  public void readYourOwnWritesCfIterIndirect() throws RocksDBException {
+    final List<ColumnFamilyDescriptor> cfNames =
+        Arrays.asList(new ColumnFamilyDescriptor(RocksDB.DEFAULT_COLUMN_FAMILY),
+            new ColumnFamilyDescriptor("new_cf".getBytes()));
+
+    final List<ColumnFamilyHandle> columnFamilyHandleList = new ArrayList<>();
+
+    // Test open database with column family names
+    try (final DBOptions options =
+             new DBOptions().setCreateIfMissing(true).setCreateMissingColumnFamilies(true);
+         final RocksDB db = RocksDB.open(
+             options, dbFolder.getRoot().getAbsolutePath(), cfNames, columnFamilyHandleList)) {
+      final ColumnFamilyHandle newCf = columnFamilyHandleList.get(1);
+
+      try {
+        final byte[] kv1 = "key1".getBytes();
+        final byte[] vv1 = "value1".getBytes();
+        final ByteBuffer k1 = ByteBuffer.allocate(12);
+        k1.put(kv1).flip();
+        final byte[] kv2 = "key2".getBytes();
+        final byte[] vv2 = "value2".getBytes();
+        final ByteBuffer k2 = ByteBuffer.allocate(12);
+        k2.put(kv2).flip();
+
+        db.put(newCf, kv1, vv1);
+        db.put(newCf, kv2, vv2);
+
+        try (final WriteBatchWithIndex wbwi = new WriteBatchWithIndex(true);
+             final ReadOptions readOptions = new ReadOptions();
+             final RocksIterator base = db.newIterator(newCf, readOptions);
+             final RocksIterator it = wbwi.newIteratorWithBase(newCf, base, readOptions)) {
+          it.seek(k1);
+          assertThat(it.isValid()).isTrue();
+          assertThat(it.key()).isEqualTo(kv1);
+          assertThat(it.value()).isEqualTo(vv1);
+
+          it.seek(k2);
+          assertThat(it.isValid()).isTrue();
+          assertThat(it.key()).isEqualTo(kv2);
+          assertThat(it.value()).isEqualTo(vv2);
+
+          // put data to the write batch and make sure we can read it.
+          final byte[] kv3 = "key3".getBytes();
+          final ByteBuffer k3 = ByteBuffer.allocate(12);
+          k3.put(kv3);
+          final byte[] vv3 = "value3".getBytes();
+          wbwi.put(newCf, kv3, vv3);
+          k3.flip();
+          it.seek(k3);
+          assertThat(it.isValid()).isTrue();
+          assertThat(it.key()).isEqualTo(kv3);
+          assertThat(it.value()).isEqualTo(vv3);
+
+          // update k2 in the write batch and check the value
+          final byte[] v2Other = "otherValue2".getBytes();
+          wbwi.put(newCf, kv2, v2Other);
+          k2.flip();
+          it.seek(k2);
+          assertThat(it.isValid()).isTrue();
+          assertThat(it.key()).isEqualTo(kv2);
+          assertThat(it.value()).isEqualTo(v2Other);
+
+          // delete k1 and make sure we can read back the write
+          wbwi.delete(newCf, kv1);
+          k1.flip();
+          it.seek(k1);
+          assertThat(it.key()).isNotEqualTo(kv1);
+
+          // reinsert k1 and make sure we see the new value
+          final byte[] v1Other = "otherValue1".getBytes();
+          wbwi.put(newCf, kv1, v1Other);
+          k1.flip();
+          it.seek(k1);
+          assertThat(it.isValid()).isTrue();
+          assertThat(it.key()).isEqualTo(kv1);
+          assertThat(it.value()).isEqualTo(v1Other);
+
+          // single remove k3 and make sure we can read back the write
+          wbwi.singleDelete(newCf, kv3);
+          k3.flip();
+          it.seek(k3);
+          assertThat(it.isValid()).isEqualTo(false);
+
+          // reinsert k3 and make sure we see the new value
+          final byte[] v3Other = "otherValue3".getBytes();
+          wbwi.put(newCf, kv3, v3Other);
+          k3.flip();
+          it.seek(k3);
+          assertThat(it.isValid()).isTrue();
+          assertThat(it.key()).isEqualTo(kv3);
+          assertThat(it.value()).isEqualTo(v3Other);
+        }
+      } finally {
+        for (final ColumnFamilyHandle columnFamilyHandle : columnFamilyHandleList) {
+          columnFamilyHandle.close();
+        }
+      }
+    }
+  }
+
   @Test
   public void writeBatchWithIndex() throws RocksDBException {
     try (final Options options = new Options().setCreateIfMissing(true);
@@ -220,10 +451,10 @@ public class WriteBatchWithIndexTest {
   public void write_writeBatchWithIndexDirect() throws RocksDBException {
     try (final Options options = new Options().setCreateIfMissing(true);
          final RocksDB db = RocksDB.open(options, dbFolder.getRoot().getAbsolutePath())) {
-      ByteBuffer k1 = ByteBuffer.allocateDirect(16);
+      final ByteBuffer k1 = ByteBuffer.allocateDirect(16);
-      ByteBuffer v1 = ByteBuffer.allocateDirect(16);
+      final ByteBuffer v1 = ByteBuffer.allocateDirect(16);
-      ByteBuffer k2 = ByteBuffer.allocateDirect(16);
+      final ByteBuffer k2 = ByteBuffer.allocateDirect(16);
-      ByteBuffer v2 = ByteBuffer.allocateDirect(16);
+      final ByteBuffer v2 = ByteBuffer.allocateDirect(16);
       k1.put("key1".getBytes()).flip();
       v1.put("value1".getBytes()).flip();
       k2.put("key2".getBytes()).flip();
@@ -258,8 +489,6 @@ public class WriteBatchWithIndexTest {
       final String v3 = "value3";
       final String k4 = "key4";
       final String k5 = "key5";
-      final String k6 = "key6";
-      final String k7 = "key7";
       final String v8 = "value8";
       final byte[] k1b = k1.getBytes(UTF_8);
       final byte[] v1b = v1.getBytes(UTF_8);
@@ -269,10 +498,11 @@ public class WriteBatchWithIndexTest {
       final byte[] v3b = v3.getBytes(UTF_8);
       final byte[] k4b = k4.getBytes(UTF_8);
       final byte[] k5b = k5.getBytes(UTF_8);
-      final byte[] k6b = k6.getBytes(UTF_8);
-      final byte[] k7b = k7.getBytes(UTF_8);
       final byte[] v8b = v8.getBytes(UTF_8);
 
+      final String k1point5 = "key1point5";
+      final String k2point5 = "key2point5";
+
       // add put records
       wbwi.put(k1b, v1b);
       wbwi.put(k2b, v2b);
@@ -303,9 +533,7 @@ public class WriteBatchWithIndexTest {
       try (final WBWIRocksIterator it = wbwi.newIterator()) {
         //direct access - seek to key offsets
         final int[] testOffsets = {2, 0, 3, 4, 1};
-
+        for (final int testOffset : testOffsets) {
-        for (int i = 0; i < testOffsets.length; i++) {
-          final int testOffset = testOffsets[i];
           final byte[] key = toArray(expected[testOffset].getKey().data());
 
           it.seek(key);
@@ -313,13 +541,94 @@ public class WriteBatchWithIndexTest {
 
           final WBWIRocksIterator.WriteEntry entry = it.entry();
           assertThat(entry).isEqualTo(expected[testOffset]);
+        }
+
+        for (final int testOffset : testOffsets) {
+          final byte[] key = toArray(expected[testOffset].getKey().data());
 
           // Direct buffer seek
-          expected[testOffset].getKey().data().mark();
+          final ByteBuffer db = expected[testOffset].getKey().data();
-          ByteBuffer db = expected[testOffset].getKey().data();
           it.seek(db);
           assertThat(db.position()).isEqualTo(key.length);
           assertThat(it.isValid()).isTrue();
+
+          final WBWIRocksIterator.WriteEntry entry = it.entry();
+          assertThat(entry).isEqualTo(expected[testOffset]);
+        }
+
+        for (final int testOffset : testOffsets) {
+          final byte[] key = toArray(expected[testOffset].getKey().data());
+
+          // Direct buffer seek
+          final ByteBuffer db = expected[testOffset].getKey().data();
+          it.seekForPrev(db);
+          assertThat(db.position()).isEqualTo(key.length);
+          assertThat(it.isValid()).isTrue();
+
+          final WBWIRocksIterator.WriteEntry entry = it.entry();
+          assertThat(entry).isEqualTo(expected[testOffset]);
+        }
+
+        for (final int testOffset : testOffsets) {
+          final byte[] key = toArray(expected[testOffset].getKey().data());
+
+          // Indirect buffer seek
+          final ByteBuffer db = ByteBuffer.allocate(key.length);
+          System.arraycopy(key, 0, db.array(), 0, key.length);
+          it.seek(db);
+          assertThat(db.position()).isEqualTo(key.length);
+          assertThat(it.isValid()).isTrue();
+
+          final WBWIRocksIterator.WriteEntry entry = it.entry();
+          assertThat(entry).isEqualTo(expected[testOffset]);
+        }
+
+        for (final int testOffset : testOffsets) {
+          final byte[] key = toArray(expected[testOffset].getKey().data());
+
+          // Indirect buffer seek for prev
+          final ByteBuffer db = ByteBuffer.allocate(key.length);
+          System.arraycopy(key, 0, db.array(), 0, key.length);
+          it.seekForPrev(db);
+          assertThat(db.position()).isEqualTo(key.length);
+          assertThat(it.isValid()).isTrue();
+
+          final WBWIRocksIterator.WriteEntry entry = it.entry();
+          assertThat(entry).isEqualTo(expected[testOffset]);
+        }
+
+        {
+          it.seekForPrev(k2point5.getBytes());
+          assertThat(it.isValid()).isTrue();
+          final WBWIRocksIterator.WriteEntry entry = it.entry();
+          assertThat(entry).isEqualTo(expected[1]);
+        }
+
+        {
+          it.seekForPrev(k1point5.getBytes());
+          assertThat(it.isValid()).isTrue();
+          final WBWIRocksIterator.WriteEntry entry = it.entry();
+          assertThat(entry).isEqualTo(expected[0]);
+        }
+
+        {
+          final ByteBuffer db = ByteBuffer.allocate(k2point5.length());
+          db.put(k2point5.getBytes());
+          db.flip();
+          it.seekForPrev(db);
+          assertThat(it.isValid()).isTrue();
+          final WBWIRocksIterator.WriteEntry entry = it.entry();
+          assertThat(entry).isEqualTo(expected[1]);
+        }
+
+        {
+          final ByteBuffer db = ByteBuffer.allocate(k1point5.length());
+          db.put(k1point5.getBytes());
+          db.flip();
+          it.seekForPrev(db);
+          assertThat(it.isValid()).isTrue();
+          final WBWIRocksIterator.WriteEntry entry = it.entry();
+          assertThat(entry).isEqualTo(expected[0]);
         }
 
         //forward iterative access

java/src/test/java/org/rocksdb/util/ByteBufferAllocator.java

@@ -0,0 +1,10 @@
+package org.rocksdb.util;
+
+import java.nio.ByteBuffer;
+
+public interface ByteBufferAllocator {
+  ByteBuffer allocate(int capacity);
+
+  ByteBufferAllocator DIRECT = new DirectByteBufferAllocator();
+  ByteBufferAllocator HEAP = new HeapByteBufferAllocator();
+}

java/src/test/java/org/rocksdb/util/DirectByteBufferAllocator.java

@@ -0,0 +1,12 @@
+package org.rocksdb.util;
+
+import java.nio.ByteBuffer;
+
+public final class DirectByteBufferAllocator implements ByteBufferAllocator {
+  DirectByteBufferAllocator(){};
+
+  @Override
+  public ByteBuffer allocate(final int capacity) {
+    return ByteBuffer.allocateDirect(capacity);
+  }
+}

java/src/test/java/org/rocksdb/util/HeapByteBufferAllocator.java

@@ -0,0 +1,12 @@
+package org.rocksdb.util;
+
+import java.nio.ByteBuffer;
+
+public final class HeapByteBufferAllocator implements ByteBufferAllocator {
+  HeapByteBufferAllocator(){};
+
+  @Override
+  public ByteBuffer allocate(final int capacity) {
+    return ByteBuffer.allocate(capacity);
+  }
+}