org.iq80.leveldb

Class Options

java.lang.Object

org.iq80.leveldb.Options

public class Options
extends Object

Options to control the behavior of a database

Constructor Summary

Constructors

Constructor and Description
Options()

Method Summary

Modifier and Type	Method and Description
int	blockRestartInterval()
Options	blockRestartInterval(int blockRestartInterval) Number of keys between restart points for delta encoding of keys.
int	blockSize()
Options	blockSize(int blockSize) Approximate size of user data packed per block.
long	cacheSize()
Options	cacheSize(long cacheSize) If cacheSize is zero, no block cache will be used- If non-zero, use the specified cache size for blocks.
DBComparator	comparator()
Options	comparator(DBComparator comparator) Parameters that affect behavior
CompressionType	compressionType()
Options	compressionType(CompressionType compressionType) Compress blocks using the specified compression algorithm.
boolean	createIfMissing() If true, the database will be created if it is missing.
Options	createIfMissing(boolean createIfMissing)
boolean	errorIfExists()
Options	errorIfExists(boolean errorIfExists) If true, an error is raised if the database already exists.
XFilterPolicy	filterPolicy()
Options	filterPolicy(XFilterPolicy filterPolicy) If non-null, use the specified filter policy to reduce disk reads.
static Options	fromOptions(Options options) Clone, create a copy of the provided instance of Options
Logger	logger()
Options	logger(Logger logger) Any internal progress/error information generated by the db will be written to logger if it is non-null, or to a file stored in the same directory as the DB contents if info_log is null.
int	maxFileSize()
Options	maxFileSize(int maxFileSize) Leveldb will write up to this amount of bytes to a file before switching to a new one.
int	maxOpenFiles()
Options	maxOpenFiles(int maxOpenFiles) Number of open files that can be used by the DB.
static Options	newDefaultOptions() Create an Options object with default values for all fields.
boolean	paranoidChecks()
Options	paranoidChecks(boolean paranoidChecks) If true, the implementation will do aggressive checking of the data it is processing and will stop early if it detects any errors.
boolean	reuseLogs()
Options	reuseLogs(boolean reuseLogs) If true, append to existing MANIFEST and log files when a database is opened.
int	writeBufferSize()
Options	writeBufferSize(int writeBufferSize) Parameters that affect performance

Methods inherited from class java.lang.Object

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

Constructor Detail

Options

public Options()

Method Detail

fromOptions

public static Options fromOptions(Options options)

Clone, create a copy of the provided instance of Options

newDefaultOptions

public static Options newDefaultOptions()

Create an Options object with default values for all fields.

createIfMissing

public boolean createIfMissing()

If true, the database will be created if it is missing.

createIfMissing

public Options createIfMissing(boolean createIfMissing)

errorIfExists

public boolean errorIfExists()

errorIfExists

public Options errorIfExists(boolean errorIfExists)

If true, an error is raised if the database already exists.

writeBufferSize

public int writeBufferSize()

writeBufferSize

public Options writeBufferSize(int writeBufferSize)

Parameters that affect performance

Amount of data to build up in memory (backed by an unsorted log on disk) before converting to a sorted on-disk file.

Larger values increase performance, especially during bulk loads. Up to two write buffers may be held in memory at the same time, so you may wish to adjust this parameter to control memory usage. Also, a larger write buffer will result in a longer recovery time the next time the database is opened.

maxOpenFiles

public int maxOpenFiles()

maxOpenFiles

public Options maxOpenFiles(int maxOpenFiles)

Number of open files that can be used by the DB. You may need to increase this if your database has a large working set (budget one open file per 2MB of working set).

blockRestartInterval

public int blockRestartInterval()

blockRestartInterval

public Options blockRestartInterval(int blockRestartInterval)

Number of keys between restart points for delta encoding of keys. This parameter can be changed dynamically. Most clients should leave this parameter alone.

maxFileSize

public int maxFileSize()

maxFileSize

public Options maxFileSize(int maxFileSize)

Leveldb will write up to this amount of bytes to a file before switching to a new one. Most clients should leave this parameter alone. However if your filesystem is more efficient with larger files, you could consider increasing the value. The downside will be longer compactions and hence longer latency/performance hiccups. Another reason to increase this parameter might be when you are initially populating a large database.

Default: 2MB

Parameters:

maxFileSize - max file size int bytes

blockSize

public int blockSize()

blockSize

public Options blockSize(int blockSize)

Approximate size of user data packed per block. Note that the block size specified here corresponds to uncompressed data. The actual size of the unit read from disk may be smaller if compression is enabled. This parameter can be changed dynamically.

compressionType

public CompressionType compressionType()

compressionType

public Options compressionType(CompressionType compressionType)

Compress blocks using the specified compression algorithm. This parameter can be changed dynamically.

Default: CompressionType.SNAPPY, which gives lightweight but fast compression.

Typical speeds of CompressionType.SNAPPY on an Intel(R) Core(TM)2 2.4GHz: ~200-500MB/s compression ~400-800MB/s decompression Note that these speeds are significantly faster than most persistent storage speeds, and therefore it is typically never worth switching to CompressionType.NONE. Even if the input data is incompressible, the CompressionType.SNAPPY implementation will efficiently detect that and will switch to uncompressed mode.

If Snappy compression is not available, CompressionType.NONE will be used.

cacheSize

public long cacheSize()

cacheSize

public Options cacheSize(long cacheSize)

If cacheSize is zero, no block cache will be used- If non-zero, use the specified cache size for blocks. By default leveldb will automatically create and use an 8MB internal cache.

comparator

public DBComparator comparator()

comparator

public Options comparator(DBComparator comparator)

Parameters that affect behavior

Comparator used to define the order of keys in the table. Default: a comparator that uses lexicographic byte-wise ordering

REQUIRES: The client must ensure that the comparator supplied here has the same name and orders keys *exactly* the same as the comparator provided to previous open calls on the same DB.

logger

public Logger logger()

logger

public Options logger(Logger logger)

Any internal progress/error information generated by the db will be written to logger if it is non-null, or to a file stored in the same directory as the DB contents if info_log is null.

paranoidChecks

public boolean paranoidChecks()

paranoidChecks

public Options paranoidChecks(boolean paranoidChecks)

If true, the implementation will do aggressive checking of the data it is processing and will stop early if it detects any errors. This may have unforeseen ramifications: for example, a corruption of one DB entry may cause a large number of entries to become unreadable or for the entire DB to become unopenable.

filterPolicy

public Options filterPolicy(XFilterPolicy filterPolicy)

If non-null, use the specified filter policy to reduce disk reads. Many applications will benefit from passing an instance of BloomFilter

Parameters:

filterPolicy - new filter policy

Returns:

self

filterPolicy

public XFilterPolicy filterPolicy()

reuseLogs

public Options reuseLogs(boolean reuseLogs)

If true, append to existing MANIFEST and log files when a database is opened. This can significantly speed up open.

reuseLogs

public boolean reuseLogs()