Make RocksDB instance responsible for closing associated ColumnFamilyHandle instances (#7428)

Summary:
- Takes the burden off developer to close ColumnFamilyHandle instances before closing RocksDB instance
- The change is backward-compatible

----
Previously the pattern for working with Column Families was:

```java
try (final ColumnFamilyOptions cfOpts = new ColumnFamilyOptions().optimizeUniversalStyleCompaction()) {

  // list of column family descriptors, first entry must always be default column family
  final List<ColumnFamilyDescriptor> cfDescriptors = Arrays.asList(
      new ColumnFamilyDescriptor(RocksDB.DEFAULT_COLUMN_FAMILY, cfOpts),
      new ColumnFamilyDescriptor("my-first-columnfamily".getBytes(), cfOpts)
  );

  // a list which will hold the handles for the column families once the db is opened
  final List<ColumnFamilyHandle> columnFamilyHandleList =
      new ArrayList<>();

  try (final DBOptions options = new DBOptions()
      .setCreateIfMissing(true)
      .setCreateMissingColumnFamilies(true);
       final RocksDB db = RocksDB.open(options,
           "path/to/do", cfDescriptors,
           columnFamilyHandleList)) {

    try {

      // do something

    } finally {

      // NOTE user must explicitly frees the column family handles before freeing the db
      for (final ColumnFamilyHandle columnFamilyHandle :
          columnFamilyHandleList) {
        columnFamilyHandle.close();
      }
    } // frees the column family options
  }
} // frees the db and the db options
```

With the changes in this PR, the Java user no longer has to worry about manually closing the Column Families, which allows them to write simpler symmetrical create/free oriented code like this:

```java
try (final ColumnFamilyOptions cfOpts = new ColumnFamilyOptions().optimizeUniversalStyleCompaction()) {

  // list of column family descriptors, first entry must always be default column family
  final List<ColumnFamilyDescriptor> cfDescriptors = Arrays.asList(
      new ColumnFamilyDescriptor(RocksDB.DEFAULT_COLUMN_FAMILY, cfOpts),
      new ColumnFamilyDescriptor("my-first-columnfamily".getBytes(), cfOpts)
  );

  // a list which will hold the handles for the column families once the db is opened
  final List<ColumnFamilyHandle> columnFamilyHandleList =
      new ArrayList<>();

  try (final DBOptions options = new DBOptions()
      .setCreateIfMissing(true)
      .setCreateMissingColumnFamilies(true);
       final RocksDB db = RocksDB.open(options,
           "path/to/do", cfDescriptors,
           columnFamilyHandleList)) {

        // do something

    } // frees the column family options, then frees the db and the db options
  }
}
```

**NOTE**: The changes in this PR are backwards API compatible, which means existing code using the original approach will also continue to function correctly.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7428

Reviewed By: cheng-chang

Differential Revision: D24063348

Pulled By: jay-zhuang

fbshipit-source-id: 648d7526669923128c863ead94516bf4d50ac658

java/src/main/java/org/rocksdb/ColumnFamilyHandle.java

@@ -13,6 +13,12 @@ import java.util.Objects;
  * ColumnFamily Pointers.
  */
 public class ColumnFamilyHandle extends RocksObject {
+  /**
+   * Constructs column family Java object, which operates on underlying native object.
+   *
+   * @param rocksDB db instance associated with this column family
+   * @param nativeHandle native handle to underlying native ColumnFamily object
+   */
   ColumnFamilyHandle(final RocksDB rocksDB,
       final long nativeHandle) {
     super(nativeHandle);

java/src/main/java/org/rocksdb/RocksDB.java

@@ -38,6 +38,8 @@ public class RocksDB extends RocksObject {
     RocksDB.loadLibrary();
   }
 
+  private List<ColumnFamilyHandle> ownedColumnFamilyHandles = new ArrayList<>();
+
   /**
    * Loads the necessary library files.
    * Calling this method twice will have no effect.
@@ -307,9 +309,12 @@ public class RocksDB extends RocksObject {
     db.storeOptionsInstance(options);
 
     for (int i = 1; i < handles.length; i++) {
-      columnFamilyHandles.add(new ColumnFamilyHandle(db, handles[i]));
+      final ColumnFamilyHandle columnFamilyHandle = new ColumnFamilyHandle(db, handles[i]);
+      columnFamilyHandles.add(columnFamilyHandle);
     }
 
+    db.ownedColumnFamilyHandles.addAll(columnFamilyHandles);
+
     return db;
   }
 
@@ -484,9 +489,12 @@ public class RocksDB extends RocksObject {
     db.storeOptionsInstance(options);
 
     for (int i = 1; i < handles.length; i++) {
-      columnFamilyHandles.add(new ColumnFamilyHandle(db, handles[i]));
+      final ColumnFamilyHandle columnFamilyHandle = new ColumnFamilyHandle(db, handles[i]);
+      columnFamilyHandles.add(columnFamilyHandle);
     }
 
+    db.ownedColumnFamilyHandles.addAll(columnFamilyHandles);
+
     return db;
   }
 
@@ -577,9 +585,12 @@ public class RocksDB extends RocksObject {
     db.storeOptionsInstance(options);
 
     for (int i = 1; i < handles.length; i++) {
-      columnFamilyHandles.add(new ColumnFamilyHandle(db, handles[i]));
+      final ColumnFamilyHandle columnFamilyHandle = new ColumnFamilyHandle(db, handles[i]);
+      columnFamilyHandles.add(columnFamilyHandle);
     }
 
+    db.ownedColumnFamilyHandles.addAll(columnFamilyHandles);
+
     return db;
   }
 
@@ -597,6 +608,11 @@ public class RocksDB extends RocksObject {
    * @throws RocksDBException if an error occurs whilst closing.
    */
   public void closeE() throws RocksDBException {
+    for (final ColumnFamilyHandle columnFamilyHandle : ownedColumnFamilyHandles) {
+      columnFamilyHandle.close();
+    }
+    ownedColumnFamilyHandles.clear();
+
     if (owningHandle_.compareAndSet(true, false)) {
       try {
         closeDatabase(nativeHandle_);
@@ -619,6 +635,11 @@ public class RocksDB extends RocksObject {
    */
   @Override
   public void close() {
+    for (final ColumnFamilyHandle columnFamilyHandle : ownedColumnFamilyHandles) {
+      columnFamilyHandle.close();
+    }
+    ownedColumnFamilyHandles.clear();
+
     if (owningHandle_.compareAndSet(true, false)) {
       try {
         closeDatabase(nativeHandle_);
@@ -661,10 +682,12 @@ public class RocksDB extends RocksObject {
   public ColumnFamilyHandle createColumnFamily(
       final ColumnFamilyDescriptor columnFamilyDescriptor)
       throws RocksDBException {
-    return new ColumnFamilyHandle(this, createColumnFamily(nativeHandle_,
-        columnFamilyDescriptor.getName(),
+    final ColumnFamilyHandle columnFamilyHandle = new ColumnFamilyHandle(this,
+        createColumnFamily(nativeHandle_, columnFamilyDescriptor.getName(),
             columnFamilyDescriptor.getName().length,
             columnFamilyDescriptor.getOptions().nativeHandle_));
+    ownedColumnFamilyHandles.add(columnFamilyHandle);
+    return columnFamilyHandle;
   }
 
   /**
@@ -688,8 +711,10 @@ public class RocksDB extends RocksObject {
     final List<ColumnFamilyHandle> columnFamilyHandles =
         new ArrayList<>(cfHandles.length);
     for (int i = 0; i < cfHandles.length; i++) {
-      columnFamilyHandles.add(new ColumnFamilyHandle(this, cfHandles[i]));
+      final ColumnFamilyHandle columnFamilyHandle = new ColumnFamilyHandle(this, cfHandles[i]);
+      columnFamilyHandles.add(columnFamilyHandle);
     }
+    ownedColumnFamilyHandles.addAll(columnFamilyHandles);
     return columnFamilyHandles;
   }
 
@@ -719,8 +744,10 @@ public class RocksDB extends RocksObject {
     final List<ColumnFamilyHandle> columnFamilyHandles =
         new ArrayList<>(cfHandles.length);
     for (int i = 0; i < cfHandles.length; i++) {
-      columnFamilyHandles.add(new ColumnFamilyHandle(this, cfHandles[i]));
+      final ColumnFamilyHandle columnFamilyHandle = new ColumnFamilyHandle(this, cfHandles[i]);
+      columnFamilyHandles.add(columnFamilyHandle);
     }
+    ownedColumnFamilyHandles.addAll(columnFamilyHandles);
     return columnFamilyHandles;
   }
 
@@ -753,7 +780,22 @@ public class RocksDB extends RocksObject {
     dropColumnFamilies(nativeHandle_, cfHandles);
   }
 
-  //TODO(AR) what about DestroyColumnFamilyHandle
+  /**
+   * Deletes native column family handle of given {@link ColumnFamilyHandle} Java object
+   * and removes reference from {@link RocksDB#ownedColumnFamilyHandles}.
+   *
+   * @param columnFamilyHandle column family handle object.
+   */
+  public void destroyColumnFamilyHandle(final ColumnFamilyHandle columnFamilyHandle) {
+    for (int i = 0; i < ownedColumnFamilyHandles.size(); ++i) {
+      final ColumnFamilyHandle ownedHandle = ownedColumnFamilyHandles.get(i);
+      if (ownedHandle.equals(columnFamilyHandle)) {
+        columnFamilyHandle.close();
+        ownedColumnFamilyHandles.remove(i);
+        return;
+      }
+    }
+  }
 
   /**
    * Set the database entry for "key" to "value".
@@ -4479,7 +4521,6 @@ public class RocksDB extends RocksObject {
       final long handle, final long cfHandle) throws RocksDBException;
   private native void dropColumnFamilies(final long handle,
       final long[] cfHandles) throws RocksDBException;
-  //TODO(AR) best way to express DestroyColumnFamilyHandle? ...maybe in ColumnFamilyHandle?
   private native void put(final long handle, final byte[] key,
       final int keyOffset, final int keyLength, final byte[] value,
       final int valueOffset, int valueLength) throws RocksDBException;

java/src/test/java/org/rocksdb/ColumnFamilyTest.java

@@ -5,16 +5,17 @@
 
 package org.rocksdb;
 
-import java.util.*;
+import static java.nio.charset.StandardCharsets.UTF_8;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
 
+import java.util.*;
 import org.junit.ClassRule;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
 
-import static java.nio.charset.StandardCharsets.UTF_8;
-import static org.assertj.core.api.Assertions.assertThat;
-
 public class ColumnFamilyTest {
 
   @ClassRule
@@ -141,33 +142,19 @@ public class ColumnFamilyTest {
          final RocksDB db = RocksDB.open(options,
              dbFolder.getRoot().getAbsolutePath(), cfNames,
              columnFamilyHandleList)) {
-
-      try {
       assertThat(columnFamilyHandleList.size()).isEqualTo(2);
       db.put("dfkey1".getBytes(), "dfvalue".getBytes());
-        db.put(columnFamilyHandleList.get(0), "dfkey2".getBytes(),
-            "dfvalue".getBytes());
-        db.put(columnFamilyHandleList.get(1), "newcfkey1".getBytes(),
-            "newcfvalue".getBytes());
+      db.put(columnFamilyHandleList.get(0), "dfkey2".getBytes(), "dfvalue".getBytes());
+      db.put(columnFamilyHandleList.get(1), "newcfkey1".getBytes(), "newcfvalue".getBytes());
 
-        String retVal = new String(db.get(columnFamilyHandleList.get(1),
-            "newcfkey1".getBytes()));
+      String retVal = new String(db.get(columnFamilyHandleList.get(1), "newcfkey1".getBytes()));
       assertThat(retVal).isEqualTo("newcfvalue");
-        assertThat((db.get(columnFamilyHandleList.get(1),
-            "dfkey1".getBytes()))).isNull();
+      assertThat((db.get(columnFamilyHandleList.get(1), "dfkey1".getBytes()))).isNull();
       db.delete(columnFamilyHandleList.get(1), "newcfkey1".getBytes());
-        assertThat((db.get(columnFamilyHandleList.get(1),
-            "newcfkey1".getBytes()))).isNull();
-        db.delete(columnFamilyHandleList.get(0), new WriteOptions(),
-            "dfkey2".getBytes());
-        assertThat(db.get(columnFamilyHandleList.get(0), new ReadOptions(),
-            "dfkey2".getBytes())).isNull();
-      } finally {
-        for (final ColumnFamilyHandle columnFamilyHandle :
-            columnFamilyHandleList) {
-          columnFamilyHandle.close();
-        }
-      }
+      assertThat((db.get(columnFamilyHandleList.get(1), "newcfkey1".getBytes()))).isNull();
+      db.delete(columnFamilyHandleList.get(0), new WriteOptions(), "dfkey2".getBytes());
+      assertThat(db.get(columnFamilyHandleList.get(0), new ReadOptions(), "dfkey2".getBytes()))
+          .isNull();
     }
   }
 
@@ -184,30 +171,22 @@ public class ColumnFamilyTest {
          final RocksDB db = RocksDB.open(options,
              dbFolder.getRoot().getAbsolutePath(), cfDescriptors,
              columnFamilyHandleList)) {
-      try {
-        db.put(columnFamilyHandleList.get(0), new WriteOptions(),
-            "key1".getBytes(), "value".getBytes());
+      db.put(
+          columnFamilyHandleList.get(0), new WriteOptions(), "key1".getBytes(), "value".getBytes());
       db.put("key2".getBytes(), "12345678".getBytes());
       final byte[] outValue = new byte[5];
       // not found value
       int getResult = db.get("keyNotFound".getBytes(), outValue);
       assertThat(getResult).isEqualTo(RocksDB.NOT_FOUND);
       // found value which fits in outValue
-        getResult = db.get(columnFamilyHandleList.get(0), "key1".getBytes(),
-            outValue);
+      getResult = db.get(columnFamilyHandleList.get(0), "key1".getBytes(), outValue);
       assertThat(getResult).isNotEqualTo(RocksDB.NOT_FOUND);
       assertThat(outValue).isEqualTo("value".getBytes());
       // found value which fits partially
-        getResult = db.get(columnFamilyHandleList.get(0), new ReadOptions(),
-            "key2".getBytes(), outValue);
+      getResult =
+          db.get(columnFamilyHandleList.get(0), new ReadOptions(), "key2".getBytes(), outValue);
       assertThat(getResult).isNotEqualTo(RocksDB.NOT_FOUND);
       assertThat(outValue).isEqualTo("12345".getBytes());
-      } finally {
-        for (final ColumnFamilyHandle columnFamilyHandle :
-            columnFamilyHandleList) {
-          columnFamilyHandle.close();
-        }
-      }
     }
   }
 
@@ -223,22 +202,12 @@ public class ColumnFamilyTest {
          final RocksDB db = RocksDB.open(options,
              dbFolder.getRoot().getAbsolutePath(), cfDescriptors,
              columnFamilyHandleList)) {
-      ColumnFamilyHandle tmpColumnFamilyHandle = null;
-      try {
+      ColumnFamilyHandle tmpColumnFamilyHandle;
       tmpColumnFamilyHandle = db.createColumnFamily(
-            new ColumnFamilyDescriptor("tmpCF".getBytes(),
-                new ColumnFamilyOptions()));
+          new ColumnFamilyDescriptor("tmpCF".getBytes(), new ColumnFamilyOptions()));
       db.put(tmpColumnFamilyHandle, "key".getBytes(), "value".getBytes());
       db.dropColumnFamily(tmpColumnFamilyHandle);
       assertThat(tmpColumnFamilyHandle.isOwningHandle()).isTrue();
-      } finally {
-        if (tmpColumnFamilyHandle != null) {
-          tmpColumnFamilyHandle.close();
-        }
-        for (ColumnFamilyHandle columnFamilyHandle : columnFamilyHandleList) {
-          columnFamilyHandle.close();
-        }
-      }
     }
   }
 
@@ -256,29 +225,15 @@ public class ColumnFamilyTest {
              columnFamilyHandleList)) {
       ColumnFamilyHandle tmpColumnFamilyHandle = null;
       ColumnFamilyHandle tmpColumnFamilyHandle2 = null;
-      try {
       tmpColumnFamilyHandle = db.createColumnFamily(
-            new ColumnFamilyDescriptor("tmpCF".getBytes(),
-                new ColumnFamilyOptions()));
+          new ColumnFamilyDescriptor("tmpCF".getBytes(), new ColumnFamilyOptions()));
       tmpColumnFamilyHandle2 = db.createColumnFamily(
-            new ColumnFamilyDescriptor("tmpCF2".getBytes(),
-                new ColumnFamilyOptions()));
+          new ColumnFamilyDescriptor("tmpCF2".getBytes(), new ColumnFamilyOptions()));
       db.put(tmpColumnFamilyHandle, "key".getBytes(), "value".getBytes());
       db.put(tmpColumnFamilyHandle2, "key".getBytes(), "value".getBytes());
       db.dropColumnFamilies(Arrays.asList(tmpColumnFamilyHandle, tmpColumnFamilyHandle2));
       assertThat(tmpColumnFamilyHandle.isOwningHandle()).isTrue();
       assertThat(tmpColumnFamilyHandle2.isOwningHandle()).isTrue();
-      } finally {
-        if (tmpColumnFamilyHandle != null) {
-          tmpColumnFamilyHandle.close();
-        }
-        if (tmpColumnFamilyHandle2 != null) {
-          tmpColumnFamilyHandle2.close();
-        }
-        for (ColumnFamilyHandle columnFamilyHandle : columnFamilyHandleList) {
-          columnFamilyHandle.close();
-        }
-      }
     }
   }
 
@@ -300,36 +255,24 @@ public class ColumnFamilyTest {
                cfDescriptors, columnFamilyHandleList);
            final WriteBatch writeBatch = new WriteBatch();
            final WriteOptions writeOpt = new WriteOptions()) {
-        try {
         writeBatch.put("key".getBytes(), "value".getBytes());
-          writeBatch.put(db.getDefaultColumnFamily(),
-              "mergeKey".getBytes(), "merge".getBytes());
-          writeBatch.merge(db.getDefaultColumnFamily(), "mergeKey".getBytes(),
-              "merge".getBytes());
-          writeBatch.put(columnFamilyHandleList.get(1), "newcfkey".getBytes(),
-              "value".getBytes());
-          writeBatch.put(columnFamilyHandleList.get(1), "newcfkey2".getBytes(),
-              "value2".getBytes());
+        writeBatch.put(db.getDefaultColumnFamily(), "mergeKey".getBytes(), "merge".getBytes());
+        writeBatch.merge(db.getDefaultColumnFamily(), "mergeKey".getBytes(), "merge".getBytes());
+        writeBatch.put(columnFamilyHandleList.get(1), "newcfkey".getBytes(), "value".getBytes());
+        writeBatch.put(columnFamilyHandleList.get(1), "newcfkey2".getBytes(), "value2".getBytes());
         writeBatch.delete("xyz".getBytes());
         writeBatch.delete(columnFamilyHandleList.get(1), "xyz".getBytes());
         db.write(writeOpt, writeBatch);
 
-          assertThat(db.get(columnFamilyHandleList.get(1),
-              "xyz".getBytes()) == null);
-          assertThat(new String(db.get(columnFamilyHandleList.get(1),
-              "newcfkey".getBytes()))).isEqualTo("value");
-          assertThat(new String(db.get(columnFamilyHandleList.get(1),
-              "newcfkey2".getBytes()))).isEqualTo("value2");
+        assertThat(db.get(columnFamilyHandleList.get(1), "xyz".getBytes()) == null);
+        assertThat(new String(db.get(columnFamilyHandleList.get(1), "newcfkey".getBytes())))
+            .isEqualTo("value");
+        assertThat(new String(db.get(columnFamilyHandleList.get(1), "newcfkey2".getBytes())))
+            .isEqualTo("value2");
         assertThat(new String(db.get("key".getBytes()))).isEqualTo("value");
         // check if key is merged
-          assertThat(new String(db.get(db.getDefaultColumnFamily(),
-              "mergeKey".getBytes()))).isEqualTo("merge,merge");
-        } finally {
-          for (final ColumnFamilyHandle columnFamilyHandle :
-              columnFamilyHandleList) {
-            columnFamilyHandle.close();
-          }
-        }
+        assertThat(new String(db.get(db.getDefaultColumnFamily(), "mergeKey".getBytes())))
+            .isEqualTo("merge,merge");
       }
     }
   }
@@ -346,14 +289,9 @@ public class ColumnFamilyTest {
          final RocksDB db = RocksDB.open(options,
              dbFolder.getRoot().getAbsolutePath(),
              cfDescriptors, columnFamilyHandleList)) {
-      try {
-
-        db.put(columnFamilyHandleList.get(1), "newcfkey".getBytes(),
-            "value".getBytes());
-        db.put(columnFamilyHandleList.get(1), "newcfkey2".getBytes(),
-            "value2".getBytes());
-        try (final RocksIterator rocksIterator =
-                 db.newIterator(columnFamilyHandleList.get(1))) {
+      db.put(columnFamilyHandleList.get(1), "newcfkey".getBytes(), "value".getBytes());
+      db.put(columnFamilyHandleList.get(1), "newcfkey2".getBytes(), "value2".getBytes());
+      try (final RocksIterator rocksIterator = db.newIterator(columnFamilyHandleList.get(1))) {
         rocksIterator.seekToFirst();
         Map<String, String> refMap = new HashMap<>();
         refMap.put("newcfkey", "value");
@@ -361,18 +299,12 @@ public class ColumnFamilyTest {
         int i = 0;
         while (rocksIterator.isValid()) {
           i++;
-            assertThat(refMap.get(new String(rocksIterator.key()))).
-                isEqualTo(new String(rocksIterator.value()));
+          assertThat(refMap.get(new String(rocksIterator.key())))
+              .isEqualTo(new String(rocksIterator.value()));
           rocksIterator.next();
         }
         assertThat(i).isEqualTo(2);
       }
-      } finally {
-        for (final ColumnFamilyHandle columnFamilyHandle :
-            columnFamilyHandleList) {
-          columnFamilyHandle.close();
-        }
-      }
     }
   }
 
@@ -388,35 +320,20 @@ public class ColumnFamilyTest {
          final RocksDB db = RocksDB.open(options,
              dbFolder.getRoot().getAbsolutePath(),
              cfDescriptors, columnFamilyHandleList)) {
-      try {
-        db.put(columnFamilyHandleList.get(0), "key".getBytes(),
-            "value".getBytes());
-        db.put(columnFamilyHandleList.get(1), "newcfkey".getBytes(),
-            "value".getBytes());
+      db.put(columnFamilyHandleList.get(0), "key".getBytes(), "value".getBytes());
+      db.put(columnFamilyHandleList.get(1), "newcfkey".getBytes(), "value".getBytes());
 
-        final List<byte[]> keys = Arrays.asList(new byte[][]{
-            "key".getBytes(), "newcfkey".getBytes()
-        });
+      final List<byte[]> keys =
+          Arrays.asList(new byte[][] {"key".getBytes(), "newcfkey".getBytes()});
 
       List<byte[]> retValues = db.multiGetAsList(columnFamilyHandleList, keys);
       assertThat(retValues.size()).isEqualTo(2);
-        assertThat(new String(retValues.get(0)))
-            .isEqualTo("value");
-        assertThat(new String(retValues.get(1)))
-            .isEqualTo("value");
-        retValues = db.multiGetAsList(new ReadOptions(), columnFamilyHandleList,
-            keys);
+      assertThat(new String(retValues.get(0))).isEqualTo("value");
+      assertThat(new String(retValues.get(1))).isEqualTo("value");
+      retValues = db.multiGetAsList(new ReadOptions(), columnFamilyHandleList, keys);
       assertThat(retValues.size()).isEqualTo(2);
-        assertThat(new String(retValues.get(0)))
-            .isEqualTo("value");
-        assertThat(new String(retValues.get(1)))
-            .isEqualTo("value");
-      } finally {
-        for (final ColumnFamilyHandle columnFamilyHandle :
-            columnFamilyHandleList) {
-          columnFamilyHandle.close();
-        }
-      }
+      assertThat(new String(retValues.get(0))).isEqualTo("value");
+      assertThat(new String(retValues.get(1))).isEqualTo("value");
     }
   }
 
@@ -432,35 +349,19 @@ public class ColumnFamilyTest {
          final RocksDB db = RocksDB.open(options,
              dbFolder.getRoot().getAbsolutePath(),
              cfDescriptors, columnFamilyHandleList)) {
-      try {
-        db.put(columnFamilyHandleList.get(0), "key".getBytes(),
-            "value".getBytes());
-        db.put(columnFamilyHandleList.get(1), "newcfkey".getBytes(),
-            "value".getBytes());
-
-        final List<byte[]> keys = Arrays.asList(new byte[][]{
-            "key".getBytes(), "newcfkey".getBytes()
-        });
-        List<byte[]> retValues = db.multiGetAsList(columnFamilyHandleList,
-            keys);
+      db.put(columnFamilyHandleList.get(0), "key".getBytes(), "value".getBytes());
+      db.put(columnFamilyHandleList.get(1), "newcfkey".getBytes(), "value".getBytes());
+
+      final List<byte[]> keys =
+          Arrays.asList(new byte[][] {"key".getBytes(), "newcfkey".getBytes()});
+      List<byte[]> retValues = db.multiGetAsList(columnFamilyHandleList, keys);
       assertThat(retValues.size()).isEqualTo(2);
-        assertThat(new String(retValues.get(0)))
-            .isEqualTo("value");
-        assertThat(new String(retValues.get(1)))
-            .isEqualTo("value");
-        retValues = db.multiGetAsList(new ReadOptions(), columnFamilyHandleList,
-            keys);
+      assertThat(new String(retValues.get(0))).isEqualTo("value");
+      assertThat(new String(retValues.get(1))).isEqualTo("value");
+      retValues = db.multiGetAsList(new ReadOptions(), columnFamilyHandleList, keys);
       assertThat(retValues.size()).isEqualTo(2);
-        assertThat(new String(retValues.get(0)))
-            .isEqualTo("value");
-        assertThat(new String(retValues.get(1)))
-            .isEqualTo("value");
-      } finally {
-        for (final ColumnFamilyHandle columnFamilyHandle :
-            columnFamilyHandleList) {
-          columnFamilyHandle.close();
-        }
-      }
+      assertThat(new String(retValues.get(0))).isEqualTo("value");
+      assertThat(new String(retValues.get(1))).isEqualTo("value");
     }
   }
 
@@ -476,30 +377,18 @@ public class ColumnFamilyTest {
          final RocksDB db = RocksDB.open(options,
              dbFolder.getRoot().getAbsolutePath(),
              cfDescriptors, columnFamilyHandleList)) {
-      try {
-        assertThat(db.getProperty("rocksdb.estimate-num-keys")).
-            isNotNull();
-        assertThat(db.getLongProperty(columnFamilyHandleList.get(0),
-            "rocksdb.estimate-num-keys")).isGreaterThanOrEqualTo(0);
+      assertThat(db.getProperty("rocksdb.estimate-num-keys")).isNotNull();
+      assertThat(db.getLongProperty(columnFamilyHandleList.get(0), "rocksdb.estimate-num-keys"))
+          .isGreaterThanOrEqualTo(0);
       assertThat(db.getProperty("rocksdb.stats")).isNotNull();
-        assertThat(db.getProperty(columnFamilyHandleList.get(0),
-            "rocksdb.sstables")).isNotNull();
-        assertThat(db.getProperty(columnFamilyHandleList.get(1),
-            "rocksdb.estimate-num-keys")).isNotNull();
-        assertThat(db.getProperty(columnFamilyHandleList.get(1),
-            "rocksdb.stats")).isNotNull();
-        assertThat(db.getProperty(columnFamilyHandleList.get(1),
-            "rocksdb.sstables")).isNotNull();
-        assertThat(db.getAggregatedLongProperty("rocksdb.estimate-num-keys")).
-            isNotNull();
-        assertThat(db.getAggregatedLongProperty("rocksdb.estimate-num-keys")).
-            isGreaterThanOrEqualTo(0);
-      } finally {
-        for (final ColumnFamilyHandle columnFamilyHandle :
-            columnFamilyHandleList) {
-          columnFamilyHandle.close();
-        }
-      }
+      assertThat(db.getProperty(columnFamilyHandleList.get(0), "rocksdb.sstables")).isNotNull();
+      assertThat(db.getProperty(columnFamilyHandleList.get(1), "rocksdb.estimate-num-keys"))
+          .isNotNull();
+      assertThat(db.getProperty(columnFamilyHandleList.get(1), "rocksdb.stats")).isNotNull();
+      assertThat(db.getProperty(columnFamilyHandleList.get(1), "rocksdb.sstables")).isNotNull();
+      assertThat(db.getAggregatedLongProperty("rocksdb.estimate-num-keys")).isNotNull();
+      assertThat(db.getAggregatedLongProperty("rocksdb.estimate-num-keys"))
+          .isGreaterThanOrEqualTo(0);
     }
   }
 
@@ -547,10 +436,6 @@ public class ColumnFamilyTest {
             rocksIterator.close();
           }
         }
-        for (final ColumnFamilyHandle columnFamilyHandle :
-            columnFamilyHandleList) {
-          columnFamilyHandle.close();
-        }
       }
     }
   }
@@ -566,15 +451,8 @@ public class ColumnFamilyTest {
          final RocksDB db = RocksDB.open(options,
              dbFolder.getRoot().getAbsolutePath(),
              cfDescriptors, columnFamilyHandleList)) {
-      try {
       db.dropColumnFamily(columnFamilyHandleList.get(1));
-        db.put(columnFamilyHandleList.get(1), "key".getBytes(),
-            "value".getBytes());
-      } finally {
-        for (ColumnFamilyHandle columnFamilyHandle : columnFamilyHandleList) {
-          columnFamilyHandle.close();
-        }
-      }
+      db.put(columnFamilyHandleList.get(1), "key".getBytes(), "value".getBytes());
     }
   }
 
@@ -589,15 +467,8 @@ public class ColumnFamilyTest {
          final RocksDB db = RocksDB.open(options,
              dbFolder.getRoot().getAbsolutePath(),
              cfDescriptors, columnFamilyHandleList)) {
-      try {
       db.dropColumnFamily(columnFamilyHandleList.get(1));
       db.delete(columnFamilyHandleList.get(1), "key".getBytes());
-      } finally {
-        for (final ColumnFamilyHandle columnFamilyHandle :
-            columnFamilyHandleList) {
-          columnFamilyHandle.close();
-        }
-      }
     }
   }
 
@@ -612,15 +483,8 @@ public class ColumnFamilyTest {
          final RocksDB db = RocksDB.open(options,
              dbFolder.getRoot().getAbsolutePath(), cfDescriptors,
              columnFamilyHandleList)) {
-      try {
       db.dropColumnFamily(columnFamilyHandleList.get(1));
       db.get(columnFamilyHandleList.get(1), "key".getBytes());
-      } finally {
-        for (final ColumnFamilyHandle columnFamilyHandle :
-            columnFamilyHandleList) {
-          columnFamilyHandle.close();
-        }
-      }
     }
   }
 
@@ -635,19 +499,11 @@ public class ColumnFamilyTest {
          final RocksDB db = RocksDB.open(options,
              dbFolder.getRoot().getAbsolutePath(), cfDescriptors,
              columnFamilyHandleList)) {
-      try {
       final List<byte[]> keys = new ArrayList<>();
       keys.add("key".getBytes());
       keys.add("newcfkey".getBytes());
       final List<ColumnFamilyHandle> cfCustomList = new ArrayList<>();
       db.multiGetAsList(cfCustomList, keys);
-
-      } finally {
-        for (final ColumnFamilyHandle columnFamilyHandle :
-            columnFamilyHandleList) {
-          columnFamilyHandle.close();
-        }
-      }
     }
   }
 
@@ -661,25 +517,12 @@ public class ColumnFamilyTest {
       final byte[] b0 = new byte[]{(byte) 0x00};
       final byte[] b1 = new byte[]{(byte) 0x01};
       final byte[] b2 = new byte[]{(byte) 0x02};
-      ColumnFamilyHandle cf1 = null, cf2 = null, cf3 = null;
-      try {
-        cf1 = db.createColumnFamily(new ColumnFamilyDescriptor(b0));
-        cf2 = db.createColumnFamily(new ColumnFamilyDescriptor(b1));
-        final List<byte[]> families = RocksDB.listColumnFamilies(options,
-            dbFolder.getRoot().getAbsolutePath());
+      db.createColumnFamily(new ColumnFamilyDescriptor(b0));
+      db.createColumnFamily(new ColumnFamilyDescriptor(b1));
+      final List<byte[]> families =
+          RocksDB.listColumnFamilies(options, dbFolder.getRoot().getAbsolutePath());
       assertThat(families).contains("default".getBytes(), b0, b1);
-        cf3 = db.createColumnFamily(new ColumnFamilyDescriptor(b2));
-      } finally {
-        if (cf1 != null) {
-          cf1.close();
-        }
-        if (cf2 != null) {
-          cf2.close();
-        }
-        if (cf3 != null) {
-          cf3.close();
-        }
-      }
+      db.createColumnFamily(new ColumnFamilyDescriptor(b2));
     }
   }
 
@@ -690,22 +533,13 @@ public class ColumnFamilyTest {
          final RocksDB db = RocksDB.open(options,
              dbFolder.getRoot().getAbsolutePath());
     ) {
-      try {
-        final byte[] b0 = new byte[]{0, 0};
-        final byte[] b1 = new byte[]{0, 1};
+      final byte[] b0 = new byte[] {0, 0};
+      final byte[] b1 = new byte[] {0, 1};
       cf1 = db.createColumnFamily(new ColumnFamilyDescriptor(b0));
       cf2 = db.createColumnFamily(new ColumnFamilyDescriptor(b1));
-        final List<byte[]> families = RocksDB.listColumnFamilies(options,
-            dbFolder.getRoot().getAbsolutePath());
+      final List<byte[]> families =
+          RocksDB.listColumnFamilies(options, dbFolder.getRoot().getAbsolutePath());
       assertThat(families).contains("default".getBytes(), b0, b1);
-      } finally {
-        if (cf1 != null) {
-          cf1.close();
-        }
-        if (cf2 != null) {
-          cf2.close();
-        }
-      }
     }
   }
 
@@ -716,17 +550,57 @@ public class ColumnFamilyTest {
          final RocksDB db = RocksDB.open(options,
              dbFolder.getRoot().getAbsolutePath());
     ) {
-      try {
       final String simplifiedChinese = "\u7b80\u4f53\u5b57";
-        columnFamilyHandle = db.createColumnFamily(
-            new ColumnFamilyDescriptor(simplifiedChinese.getBytes()));
+      columnFamilyHandle =
+          db.createColumnFamily(new ColumnFamilyDescriptor(simplifiedChinese.getBytes()));
 
-        final List<byte[]> families = RocksDB.listColumnFamilies(options,
-            dbFolder.getRoot().getAbsolutePath());
-        assertThat(families).contains("default".getBytes(),
-            simplifiedChinese.getBytes());
+      final List<byte[]> families =
+          RocksDB.listColumnFamilies(options, dbFolder.getRoot().getAbsolutePath());
+      assertThat(families).contains("default".getBytes(), simplifiedChinese.getBytes());
+    }
+  }
+
+  @Test
+  public void testDestroyColumnFamilyHandle() throws RocksDBException {
+    try (final Options options = new Options().setCreateIfMissing(true);
+         final RocksDB db = RocksDB.open(options, dbFolder.getRoot().getAbsolutePath());) {
+      final byte[] name1 = "cf1".getBytes();
+      final byte[] name2 = "cf2".getBytes();
+      final ColumnFamilyDescriptor desc1 = new ColumnFamilyDescriptor(name1);
+      final ColumnFamilyDescriptor desc2 = new ColumnFamilyDescriptor(name2);
+      final ColumnFamilyHandle cf1 = db.createColumnFamily(desc1);
+      final ColumnFamilyHandle cf2 = db.createColumnFamily(desc2);
+      assertTrue(cf1.isOwningHandle());
+      assertTrue(cf2.isOwningHandle());
+      assertFalse(cf1.isDefaultColumnFamily());
+      db.destroyColumnFamilyHandle(cf1);
+      // At this point cf1 should not be used!
+      assertFalse(cf1.isOwningHandle());
+      assertTrue(cf2.isOwningHandle());
+    }
+  }
+
+  @Test
+  @Deprecated
+  /**
+   * @deprecated Now explicitly closing instances of ColumnFamilyHandle is not required.
+   *     RocksDB instance will take care of closing its associated ColumnFamilyHandle objects.
+   */
+  public void testColumnFamilyCloseBeforeDb() 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<>();
+
+    try (final DBOptions options =
+             new DBOptions().setCreateIfMissing(true).setCreateMissingColumnFamilies(true);
+         final RocksDB db = RocksDB.open(
+             options, dbFolder.getRoot().getAbsolutePath(), cfNames, columnFamilyHandleList)) {
+      try {
+        db.put("testKey".getBytes(), "tstValue".getBytes());
+        // Do something...
       } finally {
-        if (columnFamilyHandle != null) {
+        for (final ColumnFamilyHandle columnFamilyHandle : columnFamilyHandleList) {
           columnFamilyHandle.close();
         }
       }

java/src/test/java/org/rocksdb/CompactionFilterFactoryTest.java

@@ -39,10 +39,8 @@ public class CompactionFilterFactoryTest {
 
       final List<ColumnFamilyHandle> cfHandles = new ArrayList<>();
 
-      try (final RocksDB rocksDb = RocksDB.open(options,
-               dbFolder.getRoot().getAbsolutePath(), cfNames, cfHandles);
-      ) {
-        try {
+      try (final RocksDB rocksDb =
+               RocksDB.open(options, dbFolder.getRoot().getAbsolutePath(), cfNames, cfHandles)) {
         final byte[] key1 = "key1".getBytes();
         final byte[] key2 = "key2".getBytes();
 
@@ -57,11 +55,6 @@ public class CompactionFilterFactoryTest {
         assertThat(rocksDb.get(cfHandles.get(1), key1)).isEqualTo(value1);
         final boolean exists = rocksDb.keyMayExist(cfHandles.get(1), key2, null);
         assertThat(exists).isFalse();
-        } finally {
-          for (final ColumnFamilyHandle cfHandle : cfHandles) {
-            cfHandle.close();
-          }
-        }
       }
     }
   }