org.rocksdb

Class WriteOptions

java.lang.Object

org.rocksdb.AbstractNativeReference

org.rocksdb.AbstractImmutableNativeReference

org.rocksdb.RocksObject

org.rocksdb.WriteOptions

All Implemented Interfaces:

java.lang.AutoCloseable

public class WriteOptions
extends RocksObject

Options that control write operations. Note that developers should call WriteOptions.dispose() to release the c++ side memory before a WriteOptions instance runs out of scope.

Field Summary

Fields inherited from class org.rocksdb.RocksObject

nativeHandle_

Fields inherited from class org.rocksdb.AbstractImmutableNativeReference

owningHandle_

Constructor Summary

Constructors

Constructor and Description
WriteOptions() Construct WriteOptions instance.
WriteOptions(WriteOptions other) Copy constructor for WriteOptions.

Method Summary

Methods

Modifier and Type	Method and Description
boolean	disableWAL() If true, writes will not first go to the write ahead log, and the write may got lost after a crash.
protected void	disposeInternal(long handle)
boolean	ignoreMissingColumnFamilies() If true and if user is trying to write to column families that don't exist (they were dropped), ignore the write (don't return an error).
boolean	lowPri() Returns true if this write request is of lower priority if compaction is behind.
boolean	noSlowdown() If true and we need to wait or sleep for the write request, fails immediately with Status.Code.Incomplete.
WriteOptions	setDisableWAL(boolean flag) If true, writes will not first go to the write ahead log, and the write may got lost after a crash.
WriteOptions	setIgnoreMissingColumnFamilies(boolean ignoreMissingColumnFamilies) If true and if user is trying to write to column families that don't exist (they were dropped), ignore the write (don't return an error).
WriteOptions	setLowPri(boolean lowPri) If true, this write request is of lower priority if compaction is behind.
WriteOptions	setNoSlowdown(boolean noSlowdown) If true and we need to wait or sleep for the write request, fails immediately with Status.Code.Incomplete.
WriteOptions	setSync(boolean flag) If true, the write will be flushed from the operating system buffer cache (by calling WritableFile::Sync()) before the write is considered complete.
boolean	sync() If true, the write will be flushed from the operating system buffer cache (by calling WritableFile::Sync()) before the write is considered complete.

Methods inherited from class org.rocksdb.RocksObject

disposeInternal

Methods inherited from class org.rocksdb.AbstractImmutableNativeReference

close, disOwnNativeHandle, isOwningHandle

Methods inherited from class org.rocksdb.AbstractNativeReference

dispose, finalize

Methods inherited from class java.lang.Object

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

Constructor Detail

WriteOptions

public WriteOptions()

Construct WriteOptions instance.

WriteOptions

public WriteOptions(WriteOptions other)

Copy constructor for WriteOptions. NOTE: This does a shallow copy, which means comparator, merge_operator, compaction_filter, compaction_filter_factory and other pointers will be cloned!

Parameters:

other - The ColumnFamilyOptions to copy.

Method Detail

setSync

public WriteOptions setSync(boolean flag)

If true, the write will be flushed from the operating system buffer cache (by calling WritableFile::Sync()) before the write is considered complete. If this flag is true, writes will be slower. If this flag is false, and the machine crashes, some recent writes may be lost. Note that if it is just the process that crashes (i.e., the machine does not reboot), no writes will be lost even if sync==false. In other words, a DB write with sync==false has similar crash semantics as the "write()" system call. A DB write with sync==true has similar crash semantics to a "write()" system call followed by "fdatasync()". Default: false

Parameters:

flag - a boolean flag to indicate whether a write should be synchronized.

Returns:

the instance of the current WriteOptions.

sync

public boolean sync()

If true, the write will be flushed from the operating system buffer cache (by calling WritableFile::Sync()) before the write is considered complete. If this flag is true, writes will be slower. If this flag is false, and the machine crashes, some recent writes may be lost. Note that if it is just the process that crashes (i.e., the machine does not reboot), no writes will be lost even if sync==false. In other words, a DB write with sync==false has similar crash semantics as the "write()" system call. A DB write with sync==true has similar crash semantics to a "write()" system call followed by "fdatasync()".

Returns:

boolean value indicating if sync is active.

setDisableWAL

public WriteOptions setDisableWAL(boolean flag)

If true, writes will not first go to the write ahead log, and the write may got lost after a crash. The backup engine relies on write-ahead logs to back up the memtable, so if you disable write-ahead logs, you must create backups with flush_before_backup=true to avoid losing unflushed memtable data.

Parameters:

flag - a boolean flag to specify whether to disable write-ahead-log on writes.

Returns:

the instance of the current WriteOptions.

disableWAL

public boolean disableWAL()

If true, writes will not first go to the write ahead log, and the write may got lost after a crash. The backup engine relies on write-ahead logs to back up the memtable, so if you disable write-ahead logs, you must create backups with flush_before_backup=true to avoid losing unflushed memtable data.

Returns:

boolean value indicating if WAL is disabled.

setIgnoreMissingColumnFamilies

public WriteOptions setIgnoreMissingColumnFamilies(boolean ignoreMissingColumnFamilies)

If true and if user is trying to write to column families that don't exist (they were dropped), ignore the write (don't return an error). If there are multiple writes in a WriteBatch, other writes will succeed. Default: false

Parameters:

ignoreMissingColumnFamilies - true to ignore writes to column families which don't exist

Returns:

the instance of the current WriteOptions.

ignoreMissingColumnFamilies

public boolean ignoreMissingColumnFamilies()

If true and if user is trying to write to column families that don't exist (they were dropped), ignore the write (don't return an error). If there are multiple writes in a WriteBatch, other writes will succeed. Default: false

Returns:

true if writes to column families which don't exist are ignored

setNoSlowdown

public WriteOptions setNoSlowdown(boolean noSlowdown)

If true and we need to wait or sleep for the write request, fails immediately with Status.Code.Incomplete.

Parameters:

noSlowdown - true to fail write requests if we need to wait or sleep

Returns:

the instance of the current WriteOptions.

noSlowdown

public boolean noSlowdown()

If true and we need to wait or sleep for the write request, fails immediately with Status.Code.Incomplete.

Returns:

true when write requests are failed if we need to wait or sleep

setLowPri

public WriteOptions setLowPri(boolean lowPri)

If true, this write request is of lower priority if compaction is behind. In this case that, noSlowdown() == true, the request will be cancelled immediately with Status.Code.Incomplete returned. Otherwise, it will be slowed down. The slowdown value is determined by RocksDB to guarantee it introduces minimum impacts to high priority writes. Default: false

Parameters:

lowPri - true if the write request should be of lower priority than compactions which are behind.

Returns:

the instance of the current WriteOptions.

lowPri

public boolean lowPri()

Returns true if this write request is of lower priority if compaction is behind. See setLowPri(boolean).

Returns:

true if this write request is of lower priority, false otherwise.

disposeInternal

protected final void disposeInternal(long handle)

Specified by:

disposeInternal in class RocksObject