The ability to specify a compaction filter via the Java API

java/Makefile

-NATIVE_JAVA_CLASSES = org.rocksdb.AbstractComparator\
+NATIVE_JAVA_CLASSES = org.rocksdb.AbstractCompactionFilter\
+        org.rocksdb.AbstractComparator\
 	org.rocksdb.AbstractSlice\
 	org.rocksdb.BackupableDB\
 	org.rocksdb.BackupableDBOptions\

java/rocksjni/compaction_filter.cc

+// Copyright (c) 2015, Facebook, Inc.  All rights reserved.
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+//
+// This file implements the "bridge" between Java and C++ for
+// rocksdb::CompactionFilter.
+
+#include <jni.h>
+
+#include "rocksdb/compaction_filter.h"
+
+// <editor-fold desc="org.rocksdb.AbstractCompactionFilter">
+
+/*
+ * Class:     org_rocksdb_AbstractCompactionFilter
+ * Method:    disposeInternal
+ * Signature: (J)V
+ */
+void Java_org_rocksdb_AbstractCompactionFilter_disposeInternal(
+    JNIEnv* env, jobject jobj, jlong handle) {
+  delete reinterpret_cast<rocksdb::CompactionFilter*>(handle);
+}
+// </editor-fold>

java/rocksjni/options.cc

@@ -2053,6 +2053,19 @@ void Java_org_rocksdb_ColumnFamilyOptions_setMergeOperator(
       (mergeOperatorHandle));
 }
 
+/*
+ * Class:     org_rocksdb_ColumnFamilyOptions
+ * Method:    setCompactionFilterHandle
+ * Signature: (JJ)V
+ */
+void Java_org_rocksdb_ColumnFamilyOptions_setCompactionFilterHandle__JJ(
+    JNIEnv* env, jobject jobj, jlong jopt_handle,
+    jlong jcompactionfilter_handle) {
+  reinterpret_cast<rocksdb::ColumnFamilyOptions*>(jopt_handle)->
+      compaction_filter = reinterpret_cast<rocksdb::CompactionFilter*>
+        (jcompactionfilter_handle);
+}
+
 /*
  * Class:     org_rocksdb_ColumnFamilyOptions
  * Method:    setWriteBufferSize

java/src/main/java/org/rocksdb/AbstractCompactionFilter.java

+// Copyright (c) 2015, Facebook, Inc.  All rights reserved.
+// This source code is licensed under the BSD-style license found in the
+// LICENSE file in the root directory of this source tree. An additional grant
+// of patent rights can be found in the PATENTS file in the same directory.
+package org.rocksdb;
+
+/**
+ * A CompactionFilter allows an application to modify/delete a key-value at
+ * the time of compaction.
+ *
+ * At present we just permit an overriding Java class to wrap a C++ implementation
+ */
+public abstract class AbstractCompactionFilter<T extends AbstractSlice<?>>
+    extends RocksObject {
+
+  /**
+   * Deletes underlying C++ comparator pointer.
+   *
+   * Note that this function should be called only after all
+   * RocksDB instances referencing the comparator are closed.
+   * Otherwise an undefined behavior will occur.
+   */
+  @Override protected void disposeInternal() {
+    assert(isInitialized());
+    disposeInternal(nativeHandle_);
+  }
+
+  private native void disposeInternal(long handle);
+}

java/src/main/java/org/rocksdb/ColumnFamilyOptions.java

@@ -145,6 +145,13 @@ public class ColumnFamilyOptions extends RocksObject
     return this;
   }
 
+  public ColumnFamilyOptions setCompactionFilter(
+        final AbstractCompactionFilter<? extends AbstractSlice<?>> compactionFilter) {
+    setCompactionFilterHandle(nativeHandle_, compactionFilter.nativeHandle_);
+    compactionFilter_ = compactionFilter;
+    return this;
+  }
+
   @Override
   public ColumnFamilyOptions setWriteBufferSize(final long writeBufferSize) {
     assert(isInitialized());
@@ -680,6 +687,7 @@ public class ColumnFamilyOptions extends RocksObject
       long handle, String name);
   private native void setMergeOperator(
       long handle, long mergeOperatorHandle);
+  private native void setCompactionFilterHandle(long handle, long compactionFilterHandle);
   private native void setWriteBufferSize(long handle, long writeBufferSize)
       throws IllegalArgumentException;
   private native long writeBufferSize(long handle);
@@ -803,4 +811,5 @@ public class ColumnFamilyOptions extends RocksObject
   MemTableConfig memTableConfig_;
   TableFormatConfig tableFormatConfig_;
   AbstractComparator<? extends AbstractSlice<?>> comparator_;
+  AbstractCompactionFilter<? extends AbstractSlice<?>> compactionFilter_;
 }

src.mk

@@ -246,6 +246,7 @@ JNI_NATIVE_SOURCES =                                          \
   java/rocksjni/backupablejni.cc                              \
   java/rocksjni/checkpoint.cc                                 \
   java/rocksjni/columnfamilyhandle.cc                         \
+  java/rocksjni/compaction_filter.cc                          \
   java/rocksjni/comparator.cc                                 \
   java/rocksjni/comparatorjnicallback.cc                      \
   java/rocksjni/env.cc                                        \