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// 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).
package org.rocksdb;
/**
* 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.
*/
public class WriteOptions extends RocksObject {
/**
* Construct WriteOptions instance.
*/
public WriteOptions() {
super(newWriteOptions());
}
// TODO(AR) consider ownership
WriteOptions(final long nativeHandle) {
super(nativeHandle);
disOwnNativeHandle();
}
/**
* 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!
*
* @param other The ColumnFamilyOptions to copy.
*/
public WriteOptions(WriteOptions other) {
super(copyWriteOptions(other.nativeHandle_));
}
/**
* 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
*
* @param flag a boolean flag to indicate whether a write
* should be synchronized.
* @return the instance of the current WriteOptions.
*/
public WriteOptions setSync(final boolean flag) {
setSync(nativeHandle_, flag);
return this;
}
/**
* 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()".
*
* @return boolean value indicating if sync is active.
*/
public boolean sync() {
return sync(nativeHandle_);
}
/**
* 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.
*
* @param flag a boolean flag to specify whether to disable
* write-ahead-log on writes.
* @return the instance of the current WriteOptions.
*/
public WriteOptions setDisableWAL(final boolean flag) {
setDisableWAL(nativeHandle_, flag);
return this;
}
/**
* 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.
*
* @return boolean value indicating if WAL is disabled.
*/
public boolean disableWAL() {
return disableWAL(nativeHandle_);
}
/**
* 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
*
* @param ignoreMissingColumnFamilies true to ignore writes to column families
* which don't exist
* @return the instance of the current WriteOptions.
*/
public WriteOptions setIgnoreMissingColumnFamilies(
final boolean ignoreMissingColumnFamilies) {
setIgnoreMissingColumnFamilies(nativeHandle_, ignoreMissingColumnFamilies);
return this;
}
/**
* 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
*
* @return true if writes to column families which don't exist are ignored
*/
public boolean ignoreMissingColumnFamilies() {
return ignoreMissingColumnFamilies(nativeHandle_);
}
/**
* If true and we need to wait or sleep for the write request, fails
* immediately with {@link Status.Code#Incomplete}.
*
* @param noSlowdown true to fail write requests if we need to wait or sleep
* @return the instance of the current WriteOptions.
*/
public WriteOptions setNoSlowdown(final boolean noSlowdown) {
setNoSlowdown(nativeHandle_, noSlowdown);
return this;
}
/**
* If true and we need to wait or sleep for the write request, fails
* immediately with {@link Status.Code#Incomplete}.
*
* @return true when write requests are failed if we need to wait or sleep
*/
public boolean noSlowdown() {
return noSlowdown(nativeHandle_);
}
/**
* If true, this write request is of lower priority if compaction is
* behind. In this case that, {@link #noSlowdown()} == true, the request
* will be cancelled immediately with {@link 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
*
* @param lowPri true if the write request should be of lower priority than
* compactions which are behind.
*
* @return the instance of the current WriteOptions.
*/
public WriteOptions setLowPri(final boolean lowPri) {
setLowPri(nativeHandle_, lowPri);
return this;
}
/**
* Returns true if this write request is of lower priority if compaction is
* behind.
*
* See {@link #setLowPri(boolean)}.
*
* @return true if this write request is of lower priority, false otherwise.
*/
public boolean lowPri() {
return lowPri(nativeHandle_);
}
private native static long newWriteOptions();
private native static long copyWriteOptions(long handle);
@Override protected final native void disposeInternal(final long handle);
private native void setSync(long handle, boolean flag);
private native boolean sync(long handle);
private native void setDisableWAL(long handle, boolean flag);
private native boolean disableWAL(long handle);
private native void setIgnoreMissingColumnFamilies(final long handle,
final boolean ignoreMissingColumnFamilies);
private native boolean ignoreMissingColumnFamilies(final long handle);
private native void setNoSlowdown(final long handle,
final boolean noSlowdown);
private native boolean noSlowdown(final long handle);
private native void setLowPri(final long handle, final boolean lowPri);
private native boolean lowPri(final long handle);
}
