org.rocksdb

Class WriteBatch

java.lang.Object

org.rocksdb.RocksObject

org.rocksdb.WriteBatch

public class WriteBatch
extends RocksObject

WriteBatch holds a collection of updates to apply atomically to a DB. The updates are applied in the order in which they are added to the WriteBatch. For example, the value of "key" will be "v3" after the following batch is written: batch.put("key", "v1"); batch.remove("key"); batch.put("key", "v2"); batch.put("key", "v3"); Multiple threads can invoke const methods on a WriteBatch without external synchronization, but if any of the threads may call a non-const method, all threads accessing the same WriteBatch must use external synchronization.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	WriteBatch.Handler Handler callback for iterating over the contents of a batch.

Field Summary

Fields inherited from class org.rocksdb.RocksObject

nativeHandle_

Constructor Summary

Constructors

Constructor and Description
WriteBatch() Constructs a WriteBatch instance.
WriteBatch(int reserved_bytes) Constructs a WriteBatch instance with a given size.

Method Summary

Modifier and Type	Method and Description
void	clear() Clear all updates buffered in this batch
int	count() Returns the number of updates in the batch.
protected void	disposeInternal() Delete the c++ side pointer.
void	iterate(WriteBatch.Handler handler) Support for iterating over the contents of a batch.
void	merge(byte[] key, byte[] value) Merge "value" with the existing value of "key" in the database.
void	merge(ColumnFamilyHandle columnFamilyHandle, byte[] key, byte[] value) Merge "value" with the existing value of "key" in given column family.
void	put(byte[] key, byte[] value) Store the mapping "key->value" in the database.
void	put(ColumnFamilyHandle columnFamilyHandle, byte[] key, byte[] value) Store the mapping "key->value" within given column family.
void	putLogData(byte[] blob) Append a blob of arbitrary size to the records in this batch.
void	remove(byte[] key) If the database contains a mapping for "key", erase it.
void	remove(ColumnFamilyHandle columnFamilyHandle, byte[] key) If column family contains a mapping for "key", erase it.

Methods inherited from class org.rocksdb.RocksObject

disOwnNativeHandle, dispose, finalize, isInitialized, isOwningNativeHandle

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

WriteBatch

public WriteBatch()

Constructs a WriteBatch instance.

WriteBatch

public WriteBatch(int reserved_bytes)

Constructs a WriteBatch instance with a given size.

Parameters:

reserved_bytes - reserved size for WriteBatch

Method Detail

count

public int count()

Returns the number of updates in the batch.

Returns:

number of items in WriteBatch

put

public void put(byte[] key,
                byte[] value)

Store the mapping "key->value" in the database.

Parameters:

key - the specified key to be inserted.

value - the value associated with the specified key.

put

public void put(ColumnFamilyHandle columnFamilyHandle,
                byte[] key,
                byte[] value)

Store the mapping "key->value" within given column family.

Parameters:

columnFamilyHandle - ColumnFamilyHandle instance

key - the specified key to be inserted.

value - the value associated with the specified key.

merge

public void merge(byte[] key,
                  byte[] value)

Merge "value" with the existing value of "key" in the database. "key->merge(existing, value)"

Parameters:

key - the specified key to be merged.

value - the value to be merged with the current value for the specified key.

merge

public void merge(ColumnFamilyHandle columnFamilyHandle,
                  byte[] key,
                  byte[] value)

Merge "value" with the existing value of "key" in given column family. "key->merge(existing, value)"

Parameters:

columnFamilyHandle - ColumnFamilyHandle instance

key - the specified key to be merged.

value - the value to be merged with the current value for the specified key.

remove

public void remove(byte[] key)

If the database contains a mapping for "key", erase it. Else do nothing.

Parameters:

key - Key to delete within database

remove

public void remove(ColumnFamilyHandle columnFamilyHandle,
                   byte[] key)

If column family contains a mapping for "key", erase it. Else do nothing.

Parameters:

columnFamilyHandle - ColumnFamilyHandle instance

key - Key to delete within database

putLogData

public void putLogData(byte[] blob)

Append a blob of arbitrary size to the records in this batch. The blob will be stored in the transaction log but not in any other file. In particular, it will not be persisted to the SST files. When iterating over this WriteBatch, WriteBatch::Handler::LogData will be called with the contents of the blob as it is encountered. Blobs, puts, deletes, and merges will be encountered in the same order in thich they were inserted. The blob will NOT consume sequence number(s) and will NOT increase the count of the batch Example application: add timestamps to the transaction log for use in replication.

Parameters:

blob - binary object to be inserted

iterate

public void iterate(WriteBatch.Handler handler)
             throws RocksDBException

Support for iterating over the contents of a batch.

Parameters:

handler - A handler that is called back for each update present in the batch

Throws:

RocksDBException - If we cannot iterate over the batch

clear

public void clear()

Clear all updates buffered in this batch

disposeInternal

protected void disposeInternal()

Delete the c++ side pointer.

Specified by:

disposeInternal in class RocksObject