Transaction.prepare should be public (#10412)

Summary:
The absence of a public modifier appears to be an omission. prepare() is necessary for the TM to participate as a peer in a distributed transaction.

Also add basic “yes it does work in java” tests.

Resolves https://github.com/facebook/rocksdb/issues/10283

Pull Request resolved: https://github.com/facebook/rocksdb/pull/10412

Reviewed By: ajkr

Differential Revision: D38135513

Pulled By: riversand963

fbshipit-source-id: ff52b96bc7218bc3bf12845dee49f5d8edf0e297

java/src/main/java/org/rocksdb/Transaction.java

@@ -178,7 +178,7 @@ public class Transaction extends RocksObject {
   /**
    * Prepare the current transaction for 2PC
    */
-  void prepare() throws RocksDBException {
+  public void prepare() throws RocksDBException {
     //TODO(AR) consider a Java'ish version of this function, which returns an AutoCloseable (commit)
     assert(isOwningHandle());
     prepare(nativeHandle_);

java/src/test/java/org/rocksdb/OptimisticTransactionTest.java

@@ -5,17 +5,39 @@
 
 package org.rocksdb;
 
-import org.junit.Test;
+import static java.nio.charset.StandardCharsets.UTF_8;
+import static org.assertj.core.api.Assertions.*;
 
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
-
-import static java.nio.charset.StandardCharsets.UTF_8;
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.fail;
+import org.junit.Test;
 
 public class OptimisticTransactionTest extends AbstractTransactionTest {
+  @Test
+  public void prepare_commit() throws RocksDBException {
+    final byte[] k1 = "key1".getBytes(UTF_8);
+    final byte[] v1 = "value1".getBytes(UTF_8);
+    final byte[] v12 = "value12".getBytes(UTF_8);
+
+    try (final DBContainer dbContainer = startDb();
+         final ReadOptions readOptions = new ReadOptions()) {
+      try (final Transaction txn = dbContainer.beginTransaction()) {
+        txn.put(k1, v1);
+        txn.commit();
+      }
+
+      try (final Transaction txn = dbContainer.beginTransaction()) {
+        txn.put(k1, v12);
+        txn.prepare();
+
+        failBecauseExceptionWasNotThrown(RocksDBException.class);
+      } catch (final RocksDBException e) {
+        assertThat(e.getMessage())
+            .contains("Two phase commit not supported for optimistic transactions");
+      }
+    }
+  }
 
   @Test
   public void getForUpdate_cf_conflict() throws RocksDBException {

java/src/test/java/org/rocksdb/TransactionTest.java

@@ -51,6 +51,120 @@ public class TransactionTest extends AbstractTransactionTest {
     }
   }
 
+  @Test
+  public void prepare_commit() throws RocksDBException {
+    final byte[] k1 = "key1".getBytes(UTF_8);
+    final byte[] v1 = "value1".getBytes(UTF_8);
+    final byte[] v12 = "value12".getBytes(UTF_8);
+
+    try (final DBContainer dbContainer = startDb();
+         final ReadOptions readOptions = new ReadOptions()) {
+      try (final Transaction txn = dbContainer.beginTransaction()) {
+        txn.put(k1, v1);
+        txn.commit();
+      }
+
+      try (final Transaction txn = dbContainer.beginTransaction()) {
+        txn.setName("txnPrepare1");
+        txn.put(k1, v12);
+        txn.prepare();
+        txn.commit();
+      }
+
+      try (final Transaction txn = dbContainer.beginTransaction()) {
+        assertThat(txn.get(readOptions, k1)).isEqualTo(v12);
+      }
+    }
+  }
+
+  @Test
+  public void prepare_rollback() throws RocksDBException {
+    final byte[] k1 = "key1".getBytes(UTF_8);
+    final byte[] v1 = "value1".getBytes(UTF_8);
+    final byte[] v12 = "value12".getBytes(UTF_8);
+
+    try (final DBContainer dbContainer = startDb();
+         final ReadOptions readOptions = new ReadOptions()) {
+      try (final Transaction txn = dbContainer.beginTransaction()) {
+        txn.put(k1, v1);
+        txn.commit();
+      }
+
+      try (final Transaction txn = dbContainer.beginTransaction()) {
+        txn.setName("txnPrepare1");
+        txn.put(k1, v12);
+        txn.prepare();
+        txn.rollback();
+      }
+
+      try (final Transaction txn = dbContainer.beginTransaction()) {
+        assertThat(txn.get(readOptions, k1)).isEqualTo(v1);
+      }
+    }
+  }
+
+  @Test
+  public void prepare_read_prepared_commit() throws RocksDBException {
+    final byte[] k1 = "key1".getBytes(UTF_8);
+    final byte[] v1 = "value1".getBytes(UTF_8);
+    final byte[] v12 = "value12".getBytes(UTF_8);
+
+    try (final DBContainer dbContainer = startDb();
+         final ReadOptions readOptions = new ReadOptions()) {
+      try (final Transaction txn = dbContainer.beginTransaction()) {
+        txn.put(k1, v1);
+        txn.commit();
+      }
+
+      Transaction txnPrepare;
+      txnPrepare = dbContainer.beginTransaction();
+      txnPrepare.setName("txnPrepare1");
+      txnPrepare.put(k1, v12);
+      txnPrepare.prepare();
+
+      try (final Transaction txn = dbContainer.beginTransaction()) {
+        assertThat(txn.get(readOptions, k1)).isEqualTo(v1);
+      }
+
+      txnPrepare.commit();
+
+      try (final Transaction txn = dbContainer.beginTransaction()) {
+        assertThat(txn.get(readOptions, k1)).isEqualTo(v12);
+      }
+    }
+  }
+
+  @Test
+  public void prepare_read_prepared_rollback() throws RocksDBException {
+    final byte[] k1 = "key1".getBytes(UTF_8);
+    final byte[] v1 = "value1".getBytes(UTF_8);
+    final byte[] v12 = "value12".getBytes(UTF_8);
+
+    try (final DBContainer dbContainer = startDb();
+         final ReadOptions readOptions = new ReadOptions()) {
+      try (final Transaction txn = dbContainer.beginTransaction()) {
+        txn.put(k1, v1);
+        txn.commit();
+      }
+
+      Transaction txnPrepare;
+      txnPrepare = dbContainer.beginTransaction();
+      txnPrepare.setName("txnPrepare1");
+      txnPrepare.put(k1, v12);
+      txnPrepare.prepare();
+
+      try (final Transaction txn = dbContainer.beginTransaction()) {
+        assertThat(txn.get(readOptions, k1)).isEqualTo(v1);
+      }
+
+      txnPrepare.rollback();
+
+      try (final Transaction txn = dbContainer.beginTransaction()) {
+        assertThat(txn.get(readOptions, k1)).isEqualTo(v1);
+      }
+    }
+  }
+
   @Test
   public void getForUpdate_conflict() throws RocksDBException {
     final byte[] k1 = "key1".getBytes(UTF_8);