Package org.eclipse.rdf4j.common.transaction

Enum IsolationLevels

java.lang.Object

java.lang.Enum<IsolationLevels>

org.eclipse.rdf4j.common.transaction.IsolationLevels

All Implemented Interfaces:

Serializable, Comparable<IsolationLevels>, IsolationLevel, TransactionSetting

public enum IsolationLevels
extends Enum<IsolationLevels>
implements IsolationLevel

Enumeration of Transaction IsolationLevels supported by RDF4J. Note that RDF4J stores are not required to support all levels, consult the documentatation for the specific SAIL implementation you are using to find out which levels are supported.

Author:

Jeen Broekstra, James Leigh

Enum Constant Summary

Enum Constants

Enum Constant	Description
NONE	None: the lowest isolation level; transactions can see their own changes, but may not be able to roll them back and no support for isolation among transactions is guaranteed
READ_COMMITTED	Read Committed: in this isolation level only statements from other transactions that have been committed (at some point) can be seen by this transaction.
READ_UNCOMMITTED	Read Uncommitted: transactions can be rolled back, but not necessarily isolated: concurrent transactions might see each other's uncommitted data (so-called 'dirty reads')
SERIALIZABLE	Serializable: in addition to SNAPSHOT, this isolation level requires that all other successful transactions must appear to occur either completely before or completely after a successful serializable transaction.
SNAPSHOT	Snapshot: in addition to SNAPSHOT_READ, successful transactions in this isolation level will operate against a particular dataset snapshot.
SNAPSHOT_READ	Snapshot Read: in addition to READ_COMMITTED, query results in this isolation level that are observed within a successful transaction will observe a consistent snapshot.

Field Summary

Fields inherited from interface org.eclipse.rdf4j.common.transaction.IsolationLevel

NAME

Method Summary

Modifier and Type	Method	Description
static IsolationLevel	getCompatibleIsolationLevel(IsolationLevel level, List<? extends IsolationLevel> supportedLevels)	Determines the first compatible isolation level in the list of supported levels, for the given level.
boolean	isCompatibleWith(IsolationLevel otherLevel)	Verifies if this transaction isolation level is compatible with the supplied other isolation level - that is, if this transaction isolation level offers at least the same guarantees as the other level.
static IsolationLevels	valueOf(String name)	Returns the enum constant of this type with the specified name.
static IsolationLevels[]	values()	Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.eclipse.rdf4j.common.transaction.IsolationLevel

getName, getValue

Enum Constant Details

NONE

public static final IsolationLevels NONE

None: the lowest isolation level; transactions can see their own changes, but may not be able to roll them back and no support for isolation among transactions is guaranteed

READ_UNCOMMITTED

public static final IsolationLevels READ_UNCOMMITTED

Read Uncommitted: transactions can be rolled back, but not necessarily isolated: concurrent transactions might see each other's uncommitted data (so-called 'dirty reads')

READ_COMMITTED

public static final IsolationLevels READ_COMMITTED

Read Committed: in this isolation level only statements from other transactions that have been committed (at some point) can be seen by this transaction.

SNAPSHOT_READ

public static final IsolationLevels SNAPSHOT_READ

Snapshot Read: in addition to READ_COMMITTED, query results in this isolation level that are observed within a successful transaction will observe a consistent snapshot. Changes to the data occurring while a query is evaluated will not affect that query result.

SNAPSHOT

public static final IsolationLevels SNAPSHOT

Snapshot: in addition to SNAPSHOT_READ, successful transactions in this isolation level will operate against a particular dataset snapshot. Transactions in this isolation level will see either the complete effects of other transactions (consistently throughout) or not at all.

SERIALIZABLE

public static final IsolationLevels SERIALIZABLE

Serializable: in addition to SNAPSHOT, this isolation level requires that all other successful transactions must appear to occur either completely before or completely after a successful serializable transaction.

Method Details

values

public static IsolationLevels[] values()

Returns an array containing the constants of this enum type, in the order they are declared.

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static IsolationLevels valueOf(String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

IllegalArgumentException - if this enum type has no constant with the specified name

NullPointerException - if the argument is null

isCompatibleWith

public boolean isCompatibleWith(IsolationLevel otherLevel)

Description copied from interface: IsolationLevel

Verifies if this transaction isolation level is compatible with the supplied other isolation level - that is, if this transaction isolation level offers at least the same guarantees as the other level. By definition, every transaction isolation level is compatible with itself.

Specified by:

isCompatibleWith in interface IsolationLevel

Parameters:

otherLevel - an other isolation level to check compatibility against.

Returns:

true iff this isolation level is compatible with the supplied other isolation level, false otherwise.

getCompatibleIsolationLevel

public static IsolationLevel getCompatibleIsolationLevel(IsolationLevel level,
 List<? extends IsolationLevel> supportedLevels)

Determines the first compatible isolation level in the list of supported levels, for the given level. Returns the level itself if it is in the list of supported levels. Returns null if no compatible level can be found.

Parameters:

level - the IsolationLevel for which to determine a compatible level.

supportedLevels - a list of supported isolation levels from which to select the closest compatible level.

Returns:

the given level if it occurs in the list of supported levels. Otherwise, the first compatible level in the list of supported isolation levels, or null if no compatible level can be found.

Throws:

IllegalArgumentException - if either one of the input parameters is null.