org.h2.mvstore

Class MVStore.Builder

java.lang.Object

org.h2.mvstore.MVStore.Builder

Enclosing class:

MVStore

public static final class MVStore.Builder
extends java.lang.Object

A builder for an MVStore.

Constructor Summary

Constructors

Constructor and Description
Builder() Creates new instance of MVStore.Builder.

Method Summary

Modifier and Type	Method and Description
MVStore.Builder	adoptFileStore(FileStore store)
MVStore.Builder	autoCommitBufferSize(int kb) Set the size of the write buffer, in KB disk space (for file-based stores).
MVStore.Builder	autoCommitDisabled() Disable auto-commit, by setting the auto-commit delay and auto-commit buffer size to 0.
MVStore.Builder	autoCompactFillRate(int percent) Set the auto-compact target fill rate.
MVStore.Builder	backgroundExceptionHandler(java.lang.Thread.UncaughtExceptionHandler exceptionHandler) Set the listener to be used for exceptions that occur when writing in the background thread.
MVStore.Builder	cacheConcurrency(int concurrency) Set the read cache concurrency.
MVStore.Builder	cacheSize(int mb) Set the read cache size in MB.
MVStore.Builder	compress() Compress data before writing using the LZF algorithm.
MVStore.Builder	compressHigh() Compress data before writing using the Deflate algorithm.
MVStore.Builder	encryptionKey(char[] password) Encrypt / decrypt the file using the given password.
MVStore.Builder	fileName(java.lang.String fileName) Use the following file name.
MVStore.Builder	fileStore(FileStore<?> store) Use the provided file store instead of the default one.
static MVStore.Builder	fromString(java.lang.String s) Read the configuration from a string.
MVStore.Builder	keysPerPage(int keyCount) Set the number of keys per page.
MVStore	open() Open the store.
MVStore.Builder	pageSplitSize(int pageSplitSize) Set the amount of memory a page should contain at most, in bytes, before it is split.
MVStore.Builder	readOnly() Open the file in read-only mode.
MVStore.Builder	recoveryMode() Open the file in recovery mode, where some errors may be ignored.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

Builder

public Builder()

Creates new instance of MVStore.Builder.

Method Detail

autoCommitDisabled

public MVStore.Builder autoCommitDisabled()

Disable auto-commit, by setting the auto-commit delay and auto-commit buffer size to 0.

Returns:

this

autoCommitBufferSize

public MVStore.Builder autoCommitBufferSize(int kb)

Set the size of the write buffer, in KB disk space (for file-based stores). Unless auto-commit is disabled, changes are automatically saved if there are more than this amount of changes.

The default is 1024 KB.

When the value is set to 0 or lower, data is not automatically stored.

Parameters:

kb - the write buffer size, in kilobytes

Returns:

this

autoCompactFillRate

public MVStore.Builder autoCompactFillRate(int percent)

Set the auto-compact target fill rate. If the average fill rate (the percentage of the storage space that contains active data) of the chunks is lower, then the chunks with a low fill rate are re-written. Also, if the percentage of empty space between chunks is higher than this value, then chunks at the end of the file are moved. Compaction stops if the target fill rate is reached.

The default value is 90 (90%). The value 0 disables auto-compacting.

Parameters:

percent - the target fill rate

Returns:

this

fileName

public MVStore.Builder fileName(java.lang.String fileName)

Use the following file name. If the file does not exist, it is automatically created. The parent directory already must exist.

Parameters:

fileName - the file name

Returns:

this

encryptionKey

public MVStore.Builder encryptionKey(char[] password)

Encrypt / decrypt the file using the given password. This method has no effect for in-memory stores. The password is passed as a char array so that it can be cleared as soon as possible. Please note there is still a small risk that password stays in memory (due to Java garbage collection). Also, the hashed encryption key is kept in memory as long as the file is open.

Parameters:

password - the password

Returns:

this

readOnly

public MVStore.Builder readOnly()

Open the file in read-only mode. In this case, a shared lock will be acquired to ensure the file is not concurrently opened in write mode.

If this option is not used, the file is locked exclusively.

Please note a store may only be opened once in every JVM (no matter whether it is opened in read-only or read-write mode), because each file may be locked only once in a process.

Returns:

this

keysPerPage

public MVStore.Builder keysPerPage(int keyCount)

Set the number of keys per page.

Parameters:

keyCount - the number of keys

Returns:

this

recoveryMode

public MVStore.Builder recoveryMode()

Open the file in recovery mode, where some errors may be ignored.

Returns:

this

cacheSize

public MVStore.Builder cacheSize(int mb)

Set the read cache size in MB. The default is 16 MB.

Parameters:

mb - the cache size in megabytes

Returns:

this

cacheConcurrency

public MVStore.Builder cacheConcurrency(int concurrency)

Set the read cache concurrency. The default is 16, meaning 16 segments are used.

Parameters:

concurrency - the cache concurrency

Returns:

this

compress

public MVStore.Builder compress()

Compress data before writing using the LZF algorithm. This will save about 50% of the disk space, but will slow down read and write operations slightly.

This setting only affects writes; it is not necessary to enable compression when reading, even if compression was enabled when writing.

Returns:

this

compressHigh

public MVStore.Builder compressHigh()

Compress data before writing using the Deflate algorithm. This will save more disk space, but will slow down read and write operations quite a bit.

This setting only affects writes; it is not necessary to enable compression when reading, even if compression was enabled when writing.

Returns:

this

pageSplitSize

public MVStore.Builder pageSplitSize(int pageSplitSize)

Set the amount of memory a page should contain at most, in bytes, before it is split. The default is 16 KB for persistent stores and 4 KB for in-memory stores. This is not a limit in the page size, as pages with one entry can get larger. It is just the point where pages that contain more than one entry are split.

Parameters:

pageSplitSize - the page size

Returns:

this

backgroundExceptionHandler

public MVStore.Builder backgroundExceptionHandler(java.lang.Thread.UncaughtExceptionHandler exceptionHandler)

Set the listener to be used for exceptions that occur when writing in the background thread.

Parameters:

exceptionHandler - the handler

Returns:

this

fileStore

public MVStore.Builder fileStore(FileStore<?> store)

Use the provided file store instead of the default one.

File stores passed in this way need to be open. They are not closed when closing the store.

Please note that any kind of store (including an off-heap store) is considered a "persistence", while an "in-memory store" means objects are not persisted and fully kept in the JVM heap.

Parameters:

store - the file store

Returns:

this

adoptFileStore

public MVStore.Builder adoptFileStore(FileStore store)

open

public MVStore open()

Open the store.

Returns:

the opened store

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object

fromString

public static MVStore.Builder fromString(java.lang.String s)

Read the configuration from a string.

Parameters:

s - the string representation

Returns:

the builder