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diff --git a/src/rocksdb/java/samples/src/main/java/OptimisticTransactionSample.java b/src/rocksdb/java/samples/src/main/java/OptimisticTransactionSample.java new file mode 100644 index 000000000..7e7a22e94 --- /dev/null +++ b/src/rocksdb/java/samples/src/main/java/OptimisticTransactionSample.java @@ -0,0 +1,184 @@ +// Copyright (c) 2011-present, Facebook, Inc. All rights reserved. +// This source code is licensed under both the GPLv2 (found in the +// COPYING file in the root directory) and Apache 2.0 License +// (found in the LICENSE.Apache file in the root directory). + +import org.rocksdb.*; + +import static java.nio.charset.StandardCharsets.UTF_8; + +/** + * Demonstrates using Transactions on an OptimisticTransactionDB with + * varying isolation guarantees + */ +public class OptimisticTransactionSample { + private static final String dbPath = "/tmp/rocksdb_optimistic_transaction_example"; + + public static final void main(final String args[]) throws RocksDBException { + + try(final Options options = new Options() + .setCreateIfMissing(true); + final OptimisticTransactionDB txnDb = + OptimisticTransactionDB.open(options, dbPath)) { + + try (final WriteOptions writeOptions = new WriteOptions(); + final ReadOptions readOptions = new ReadOptions()) { + + //////////////////////////////////////////////////////// + // + // Simple OptimisticTransaction Example ("Read Committed") + // + //////////////////////////////////////////////////////// + readCommitted(txnDb, writeOptions, readOptions); + + + //////////////////////////////////////////////////////// + // + // "Repeatable Read" (Snapshot Isolation) Example + // -- Using a single Snapshot + // + //////////////////////////////////////////////////////// + repeatableRead(txnDb, writeOptions, readOptions); + + + //////////////////////////////////////////////////////// + // + // "Read Committed" (Monotonic Atomic Views) Example + // --Using multiple Snapshots + // + //////////////////////////////////////////////////////// + readCommitted_monotonicAtomicViews(txnDb, writeOptions, readOptions); + } + } + } + + /** + * Demonstrates "Read Committed" isolation + */ + private static void readCommitted(final OptimisticTransactionDB txnDb, + final WriteOptions writeOptions, final ReadOptions readOptions) + throws RocksDBException { + final byte key1[] = "abc".getBytes(UTF_8); + final byte value1[] = "def".getBytes(UTF_8); + + final byte key2[] = "xyz".getBytes(UTF_8); + final byte value2[] = "zzz".getBytes(UTF_8); + + // Start a transaction + try(final Transaction txn = txnDb.beginTransaction(writeOptions)) { + // Read a key in this transaction + byte[] value = txn.get(readOptions, key1); + assert(value == null); + + // Write a key in this transaction + txn.put(key1, value1); + + // Read a key OUTSIDE this transaction. Does not affect txn. + value = txnDb.get(readOptions, key1); + assert(value == null); + + // Write a key OUTSIDE of this transaction. + // Does not affect txn since this is an unrelated key. + // If we wrote key 'abc' here, the transaction would fail to commit. + txnDb.put(writeOptions, key2, value2); + + // Commit transaction + txn.commit(); + } + } + + /** + * Demonstrates "Repeatable Read" (Snapshot Isolation) isolation + */ + private static void repeatableRead(final OptimisticTransactionDB txnDb, + final WriteOptions writeOptions, final ReadOptions readOptions) + throws RocksDBException { + + final byte key1[] = "ghi".getBytes(UTF_8); + final byte value1[] = "jkl".getBytes(UTF_8); + + // Set a snapshot at start of transaction by setting setSnapshot(true) + try(final OptimisticTransactionOptions txnOptions = + new OptimisticTransactionOptions().setSetSnapshot(true); + final Transaction txn = + txnDb.beginTransaction(writeOptions, txnOptions)) { + + final Snapshot snapshot = txn.getSnapshot(); + + // Write a key OUTSIDE of transaction + txnDb.put(writeOptions, key1, value1); + + // Read a key using the snapshot. + readOptions.setSnapshot(snapshot); + final byte[] value = txn.getForUpdate(readOptions, key1, true); + assert (value == null); + + try { + // Attempt to commit transaction + txn.commit(); + throw new IllegalStateException(); + } catch(final RocksDBException e) { + // Transaction could not commit since the write outside of the txn + // conflicted with the read! + assert(e.getStatus().getCode() == Status.Code.Busy); + } + + txn.rollback(); + } finally { + // Clear snapshot from read options since it is no longer valid + readOptions.setSnapshot(null); + } + } + + /** + * Demonstrates "Read Committed" (Monotonic Atomic Views) isolation + * + * In this example, we set the snapshot multiple times. This is probably + * only necessary if you have very strict isolation requirements to + * implement. + */ + private static void readCommitted_monotonicAtomicViews( + final OptimisticTransactionDB txnDb, final WriteOptions writeOptions, + final ReadOptions readOptions) throws RocksDBException { + + final byte keyX[] = "x".getBytes(UTF_8); + final byte valueX[] = "x".getBytes(UTF_8); + + final byte keyY[] = "y".getBytes(UTF_8); + final byte valueY[] = "y".getBytes(UTF_8); + + try (final OptimisticTransactionOptions txnOptions = + new OptimisticTransactionOptions().setSetSnapshot(true); + final Transaction txn = + txnDb.beginTransaction(writeOptions, txnOptions)) { + + // Do some reads and writes to key "x" + Snapshot snapshot = txnDb.getSnapshot(); + readOptions.setSnapshot(snapshot); + byte[] value = txn.get(readOptions, keyX); + txn.put(valueX, valueX); + + // Do a write outside of the transaction to key "y" + txnDb.put(writeOptions, keyY, valueY); + + // Set a new snapshot in the transaction + txn.setSnapshot(); + snapshot = txnDb.getSnapshot(); + readOptions.setSnapshot(snapshot); + + // Do some reads and writes to key "y" + // Since the snapshot was advanced, the write done outside of the + // transaction does not conflict. + value = txn.getForUpdate(readOptions, keyY, true); + txn.put(keyY, valueY); + + // Commit. Since the snapshot was advanced, the write done outside of the + // transaction does not prevent this transaction from Committing. + txn.commit(); + + } finally { + // Clear snapshot from read options since it is no longer valid + readOptions.setSnapshot(null); + } + } +} diff --git a/src/rocksdb/java/samples/src/main/java/RocksDBColumnFamilySample.java b/src/rocksdb/java/samples/src/main/java/RocksDBColumnFamilySample.java new file mode 100644 index 000000000..72f5731a1 --- /dev/null +++ b/src/rocksdb/java/samples/src/main/java/RocksDBColumnFamilySample.java @@ -0,0 +1,78 @@ +// Copyright (c) 2011-present, Facebook, Inc. All rights reserved. +// This source code is licensed under both the GPLv2 (found in the +// COPYING file in the root directory) and Apache 2.0 License +// (found in the LICENSE.Apache file in the root directory). + +import org.rocksdb.*; + +import java.util.ArrayList; +import java.util.List; + +public class RocksDBColumnFamilySample { + static { + RocksDB.loadLibrary(); + } + + public static void main(final String[] args) throws RocksDBException { + if (args.length < 1) { + System.out.println( + "usage: RocksDBColumnFamilySample db_path"); + System.exit(-1); + } + + final String db_path = args[0]; + + System.out.println("RocksDBColumnFamilySample"); + try(final Options options = new Options().setCreateIfMissing(true); + final RocksDB db = RocksDB.open(options, db_path)) { + + assert(db != null); + + // create column family + try(final ColumnFamilyHandle columnFamilyHandle = db.createColumnFamily( + new ColumnFamilyDescriptor("new_cf".getBytes(), + new ColumnFamilyOptions()))) { + assert (columnFamilyHandle != null); + } + } + + // open DB with two column families + final List<ColumnFamilyDescriptor> columnFamilyDescriptors = + new ArrayList<>(); + // have to open default column family + columnFamilyDescriptors.add(new ColumnFamilyDescriptor( + RocksDB.DEFAULT_COLUMN_FAMILY, new ColumnFamilyOptions())); + // open the new one, too + columnFamilyDescriptors.add(new ColumnFamilyDescriptor( + "new_cf".getBytes(), new ColumnFamilyOptions())); + final List<ColumnFamilyHandle> columnFamilyHandles = new ArrayList<>(); + try(final DBOptions options = new DBOptions(); + final RocksDB db = RocksDB.open(options, db_path, + columnFamilyDescriptors, columnFamilyHandles)) { + assert(db != null); + + try { + // put and get from non-default column family + db.put( + columnFamilyHandles.get(1), new WriteOptions(), "key".getBytes(), "value".getBytes()); + + // atomic write + try (final WriteBatch wb = new WriteBatch()) { + wb.put(columnFamilyHandles.get(0), "key2".getBytes(), + "value2".getBytes()); + wb.put(columnFamilyHandles.get(1), "key3".getBytes(), + "value3".getBytes()); + wb.delete(columnFamilyHandles.get(1), "key".getBytes()); + db.write(new WriteOptions(), wb); + } + + // drop column family + db.dropColumnFamily(columnFamilyHandles.get(1)); + } finally { + for (final ColumnFamilyHandle handle : columnFamilyHandles) { + handle.close(); + } + } + } + } +} diff --git a/src/rocksdb/java/samples/src/main/java/RocksDBSample.java b/src/rocksdb/java/samples/src/main/java/RocksDBSample.java new file mode 100644 index 000000000..ea650b141 --- /dev/null +++ b/src/rocksdb/java/samples/src/main/java/RocksDBSample.java @@ -0,0 +1,296 @@ +// Copyright (c) 2011-present, Facebook, Inc. All rights reserved. +// This source code is licensed under both the GPLv2 (found in the +// COPYING file in the root directory) and Apache 2.0 License +// (found in the LICENSE.Apache file in the root directory). + +import java.lang.IllegalArgumentException; +import java.util.Arrays; +import java.util.List; +import java.util.Map; +import java.util.ArrayList; + +import org.rocksdb.*; +import org.rocksdb.util.SizeUnit; + +public class RocksDBSample { + static { + RocksDB.loadLibrary(); + } + + public static void main(final String[] args) { + if (args.length < 1) { + System.out.println("usage: RocksDBSample db_path"); + System.exit(-1); + } + + final String db_path = args[0]; + final String db_path_not_found = db_path + "_not_found"; + + System.out.println("RocksDBSample"); + try (final Options options = new Options(); + final Filter bloomFilter = new BloomFilter(10); + final ReadOptions readOptions = new ReadOptions() + .setFillCache(false); + final Statistics stats = new Statistics(); + final RateLimiter rateLimiter = new RateLimiter(10000000,10000, 10)) { + + try (final RocksDB db = RocksDB.open(options, db_path_not_found)) { + assert (false); + } catch (final RocksDBException e) { + System.out.format("Caught the expected exception -- %s\n", e); + } + + try { + options.setCreateIfMissing(true) + .setStatistics(stats) + .setWriteBufferSize(8 * SizeUnit.KB) + .setMaxWriteBufferNumber(3) + .setMaxBackgroundJobs(10) + .setCompressionType(CompressionType.ZLIB_COMPRESSION) + .setCompactionStyle(CompactionStyle.UNIVERSAL); + } catch (final IllegalArgumentException e) { + assert (false); + } + + assert (options.createIfMissing() == true); + assert (options.writeBufferSize() == 8 * SizeUnit.KB); + assert (options.maxWriteBufferNumber() == 3); + assert (options.maxBackgroundJobs() == 10); + assert (options.compressionType() == CompressionType.ZLIB_COMPRESSION); + assert (options.compactionStyle() == CompactionStyle.UNIVERSAL); + + assert (options.memTableFactoryName().equals("SkipListFactory")); + options.setMemTableConfig( + new HashSkipListMemTableConfig() + .setHeight(4) + .setBranchingFactor(4) + .setBucketCount(2000000)); + assert (options.memTableFactoryName().equals("HashSkipListRepFactory")); + + options.setMemTableConfig( + new HashLinkedListMemTableConfig() + .setBucketCount(100000)); + assert (options.memTableFactoryName().equals("HashLinkedListRepFactory")); + + options.setMemTableConfig( + new VectorMemTableConfig().setReservedSize(10000)); + assert (options.memTableFactoryName().equals("VectorRepFactory")); + + options.setMemTableConfig(new SkipListMemTableConfig()); + assert (options.memTableFactoryName().equals("SkipListFactory")); + + options.setTableFormatConfig(new PlainTableConfig()); + // Plain-Table requires mmap read + options.setAllowMmapReads(true); + assert (options.tableFactoryName().equals("PlainTable")); + + options.setRateLimiter(rateLimiter); + + final BlockBasedTableConfig table_options = new BlockBasedTableConfig(); + Cache cache = new LRUCache(64 * 1024, 6); + table_options.setBlockCache(cache) + .setFilterPolicy(bloomFilter) + .setBlockSizeDeviation(5) + .setBlockRestartInterval(10) + .setCacheIndexAndFilterBlocks(true) + .setBlockCacheCompressed(new LRUCache(64 * 1000, 10)); + + assert (table_options.blockSizeDeviation() == 5); + assert (table_options.blockRestartInterval() == 10); + assert (table_options.cacheIndexAndFilterBlocks() == true); + + options.setTableFormatConfig(table_options); + assert (options.tableFactoryName().equals("BlockBasedTable")); + + try (final RocksDB db = RocksDB.open(options, db_path)) { + db.put("hello".getBytes(), "world".getBytes()); + + final byte[] value = db.get("hello".getBytes()); + assert ("world".equals(new String(value))); + + final String str = db.getProperty("rocksdb.stats"); + assert (str != null && !str.equals("")); + } catch (final RocksDBException e) { + System.out.format("[ERROR] caught the unexpected exception -- %s\n", e); + assert (false); + } + + try (final RocksDB db = RocksDB.open(options, db_path)) { + db.put("hello".getBytes(), "world".getBytes()); + byte[] value = db.get("hello".getBytes()); + System.out.format("Get('hello') = %s\n", + new String(value)); + + for (int i = 1; i <= 9; ++i) { + for (int j = 1; j <= 9; ++j) { + db.put(String.format("%dx%d", i, j).getBytes(), + String.format("%d", i * j).getBytes()); + } + } + + for (int i = 1; i <= 9; ++i) { + for (int j = 1; j <= 9; ++j) { + System.out.format("%s ", new String(db.get( + String.format("%dx%d", i, j).getBytes()))); + } + System.out.println(""); + } + + // write batch test + try (final WriteOptions writeOpt = new WriteOptions()) { + for (int i = 10; i <= 19; ++i) { + try (final WriteBatch batch = new WriteBatch()) { + for (int j = 10; j <= 19; ++j) { + batch.put(String.format("%dx%d", i, j).getBytes(), + String.format("%d", i * j).getBytes()); + } + db.write(writeOpt, batch); + } + } + } + for (int i = 10; i <= 19; ++i) { + for (int j = 10; j <= 19; ++j) { + assert (new String( + db.get(String.format("%dx%d", i, j).getBytes())).equals( + String.format("%d", i * j))); + System.out.format("%s ", new String(db.get( + String.format("%dx%d", i, j).getBytes()))); + } + System.out.println(""); + } + + value = db.get("1x1".getBytes()); + assert (value != null); + value = db.get("world".getBytes()); + assert (value == null); + value = db.get(readOptions, "world".getBytes()); + assert (value == null); + + final byte[] testKey = "asdf".getBytes(); + final byte[] testValue = + "asdfghjkl;'?><MNBVCXZQWERTYUIOP{+_)(*&^%$#@".getBytes(); + db.put(testKey, testValue); + byte[] testResult = db.get(testKey); + assert (testResult != null); + assert (Arrays.equals(testValue, testResult)); + assert (new String(testValue).equals(new String(testResult))); + testResult = db.get(readOptions, testKey); + assert (testResult != null); + assert (Arrays.equals(testValue, testResult)); + assert (new String(testValue).equals(new String(testResult))); + + final byte[] insufficientArray = new byte[10]; + final byte[] enoughArray = new byte[50]; + int len; + len = db.get(testKey, insufficientArray); + assert (len > insufficientArray.length); + len = db.get("asdfjkl;".getBytes(), enoughArray); + assert (len == RocksDB.NOT_FOUND); + len = db.get(testKey, enoughArray); + assert (len == testValue.length); + + len = db.get(readOptions, testKey, insufficientArray); + assert (len > insufficientArray.length); + len = db.get(readOptions, "asdfjkl;".getBytes(), enoughArray); + assert (len == RocksDB.NOT_FOUND); + len = db.get(readOptions, testKey, enoughArray); + assert (len == testValue.length); + + db.delete(testKey); + len = db.get(testKey, enoughArray); + assert (len == RocksDB.NOT_FOUND); + + // repeat the test with WriteOptions + try (final WriteOptions writeOpts = new WriteOptions()) { + writeOpts.setSync(true); + writeOpts.setDisableWAL(false); + db.put(writeOpts, testKey, testValue); + len = db.get(testKey, enoughArray); + assert (len == testValue.length); + assert (new String(testValue).equals( + new String(enoughArray, 0, len))); + } + + try { + for (final TickerType statsType : TickerType.values()) { + if (statsType != TickerType.TICKER_ENUM_MAX) { + stats.getTickerCount(statsType); + } + } + System.out.println("getTickerCount() passed."); + } catch (final Exception e) { + System.out.println("Failed in call to getTickerCount()"); + assert (false); //Should never reach here. + } + + try { + for (final HistogramType histogramType : HistogramType.values()) { + if (histogramType != HistogramType.HISTOGRAM_ENUM_MAX) { + HistogramData data = stats.getHistogramData(histogramType); + } + } + System.out.println("getHistogramData() passed."); + } catch (final Exception e) { + System.out.println("Failed in call to getHistogramData()"); + assert (false); //Should never reach here. + } + + try (final RocksIterator iterator = db.newIterator()) { + + boolean seekToFirstPassed = false; + for (iterator.seekToFirst(); iterator.isValid(); iterator.next()) { + iterator.status(); + assert (iterator.key() != null); + assert (iterator.value() != null); + seekToFirstPassed = true; + } + if (seekToFirstPassed) { + System.out.println("iterator seekToFirst tests passed."); + } + + boolean seekToLastPassed = false; + for (iterator.seekToLast(); iterator.isValid(); iterator.prev()) { + iterator.status(); + assert (iterator.key() != null); + assert (iterator.value() != null); + seekToLastPassed = true; + } + + if (seekToLastPassed) { + System.out.println("iterator seekToLastPassed tests passed."); + } + + iterator.seekToFirst(); + iterator.seek(iterator.key()); + assert (iterator.key() != null); + assert (iterator.value() != null); + + System.out.println("iterator seek test passed."); + + } + System.out.println("iterator tests passed."); + + final List<byte[]> keys = new ArrayList<>(); + try (final RocksIterator iterator = db.newIterator()) { + for (iterator.seekToLast(); iterator.isValid(); iterator.prev()) { + keys.add(iterator.key()); + } + } + + List<byte[]> values = db.multiGetAsList(keys); + assert (values.size() == keys.size()); + for (final byte[] value1 : values) { + assert (value1 != null); + } + + values = db.multiGetAsList(new ReadOptions(), keys); + assert (values.size() == keys.size()); + for (final byte[] value1 : values) { + assert (value1 != null); + } + } catch (final RocksDBException e) { + System.err.println(e); + } + } + } +} diff --git a/src/rocksdb/java/samples/src/main/java/TransactionSample.java b/src/rocksdb/java/samples/src/main/java/TransactionSample.java new file mode 100644 index 000000000..b88a68f12 --- /dev/null +++ b/src/rocksdb/java/samples/src/main/java/TransactionSample.java @@ -0,0 +1,183 @@ +// Copyright (c) 2011-present, Facebook, Inc. All rights reserved. +// This source code is licensed under both the GPLv2 (found in the +// COPYING file in the root directory) and Apache 2.0 License +// (found in the LICENSE.Apache file in the root directory). + +import org.rocksdb.*; + +import static java.nio.charset.StandardCharsets.UTF_8; + +/** + * Demonstrates using Transactions on a TransactionDB with + * varying isolation guarantees + */ +public class TransactionSample { + private static final String dbPath = "/tmp/rocksdb_transaction_example"; + + public static final void main(final String args[]) throws RocksDBException { + + try(final Options options = new Options() + .setCreateIfMissing(true); + final TransactionDBOptions txnDbOptions = new TransactionDBOptions(); + final TransactionDB txnDb = + TransactionDB.open(options, txnDbOptions, dbPath)) { + + try (final WriteOptions writeOptions = new WriteOptions(); + final ReadOptions readOptions = new ReadOptions()) { + + //////////////////////////////////////////////////////// + // + // Simple Transaction Example ("Read Committed") + // + //////////////////////////////////////////////////////// + readCommitted(txnDb, writeOptions, readOptions); + + + //////////////////////////////////////////////////////// + // + // "Repeatable Read" (Snapshot Isolation) Example + // -- Using a single Snapshot + // + //////////////////////////////////////////////////////// + repeatableRead(txnDb, writeOptions, readOptions); + + + //////////////////////////////////////////////////////// + // + // "Read Committed" (Monotonic Atomic Views) Example + // --Using multiple Snapshots + // + //////////////////////////////////////////////////////// + readCommitted_monotonicAtomicViews(txnDb, writeOptions, readOptions); + } + } + } + + /** + * Demonstrates "Read Committed" isolation + */ + private static void readCommitted(final TransactionDB txnDb, + final WriteOptions writeOptions, final ReadOptions readOptions) + throws RocksDBException { + final byte key1[] = "abc".getBytes(UTF_8); + final byte value1[] = "def".getBytes(UTF_8); + + final byte key2[] = "xyz".getBytes(UTF_8); + final byte value2[] = "zzz".getBytes(UTF_8); + + // Start a transaction + try(final Transaction txn = txnDb.beginTransaction(writeOptions)) { + // Read a key in this transaction + byte[] value = txn.get(readOptions, key1); + assert(value == null); + + // Write a key in this transaction + txn.put(key1, value1); + + // Read a key OUTSIDE this transaction. Does not affect txn. + value = txnDb.get(readOptions, key1); + assert(value == null); + + // Write a key OUTSIDE of this transaction. + // Does not affect txn since this is an unrelated key. + // If we wrote key 'abc' here, the transaction would fail to commit. + txnDb.put(writeOptions, key2, value2); + + // Commit transaction + txn.commit(); + } + } + + /** + * Demonstrates "Repeatable Read" (Snapshot Isolation) isolation + */ + private static void repeatableRead(final TransactionDB txnDb, + final WriteOptions writeOptions, final ReadOptions readOptions) + throws RocksDBException { + + final byte key1[] = "ghi".getBytes(UTF_8); + final byte value1[] = "jkl".getBytes(UTF_8); + + // Set a snapshot at start of transaction by setting setSnapshot(true) + try(final TransactionOptions txnOptions = new TransactionOptions() + .setSetSnapshot(true); + final Transaction txn = + txnDb.beginTransaction(writeOptions, txnOptions)) { + + final Snapshot snapshot = txn.getSnapshot(); + + // Write a key OUTSIDE of transaction + txnDb.put(writeOptions, key1, value1); + + // Attempt to read a key using the snapshot. This will fail since + // the previous write outside this txn conflicts with this read. + readOptions.setSnapshot(snapshot); + + try { + final byte[] value = txn.getForUpdate(readOptions, key1, true); + throw new IllegalStateException(); + } catch(final RocksDBException e) { + assert(e.getStatus().getCode() == Status.Code.Busy); + } + + txn.rollback(); + } finally { + // Clear snapshot from read options since it is no longer valid + readOptions.setSnapshot(null); + } + } + + /** + * Demonstrates "Read Committed" (Monotonic Atomic Views) isolation + * + * In this example, we set the snapshot multiple times. This is probably + * only necessary if you have very strict isolation requirements to + * implement. + */ + private static void readCommitted_monotonicAtomicViews( + final TransactionDB txnDb, final WriteOptions writeOptions, + final ReadOptions readOptions) throws RocksDBException { + + final byte keyX[] = "x".getBytes(UTF_8); + final byte valueX[] = "x".getBytes(UTF_8); + + final byte keyY[] = "y".getBytes(UTF_8); + final byte valueY[] = "y".getBytes(UTF_8); + + try (final TransactionOptions txnOptions = new TransactionOptions() + .setSetSnapshot(true); + final Transaction txn = + txnDb.beginTransaction(writeOptions, txnOptions)) { + + // Do some reads and writes to key "x" + Snapshot snapshot = txnDb.getSnapshot(); + readOptions.setSnapshot(snapshot); + byte[] value = txn.get(readOptions, keyX); + txn.put(valueX, valueX); + + // Do a write outside of the transaction to key "y" + txnDb.put(writeOptions, keyY, valueY); + + // Set a new snapshot in the transaction + txn.setSnapshot(); + txn.setSavePoint(); + snapshot = txnDb.getSnapshot(); + readOptions.setSnapshot(snapshot); + + // Do some reads and writes to key "y" + // Since the snapshot was advanced, the write done outside of the + // transaction does not conflict. + value = txn.getForUpdate(readOptions, keyY, true); + txn.put(keyY, valueY); + + // Decide we want to revert the last write from this transaction. + txn.rollbackToSavePoint(); + + // Commit. + txn.commit(); + } finally { + // Clear snapshot from read options since it is no longer valid + readOptions.setSnapshot(null); + } + } +} |