org.neo4j.storageengine.api

Interface StorageEngine

public interface StorageEngine

A StorageEngine provides the functionality to durably store data, and read it back.

Method Summary

Modifier and Type	Method and Description
void	apply(CommandsToApply batch, TransactionApplicationMode mode) Apply a batch of groups of commands to this storage.
CommandReaderFactory	commandReaderFactory()
void	createCommands(Collection<StorageCommand> target, ReadableTransactionState state, StorageStatement storageStatement, ResourceLocker locks, long lastTransactionIdWhenStarted) Generates a list of commands representing the changes in the given transaction state (state and legacyIndexTransactionState.
void	flushAndForce(org.neo4j.io.pagecache.IOLimiter limiter) Flushes and forces all changes down to underlying storage.
void	forceClose() Force close all opened resources.
void	loadSchemaCache() Deprecated.
void	prepareForRecoveryRequired() Startup process have reached the conclusion that recovery is required.
void	registerDiagnostics(org.neo4j.kernel.info.DiagnosticsManager diagnosticsManager) Registers diagnostics about the storage onto DiagnosticsManager.
StoreReadLayer	storeReadLayer()

Method Detail

storeReadLayer

StoreReadLayer storeReadLayer()

Returns:

an interface for accessing data previously applied to this storage.

createCommands

void createCommands(Collection<StorageCommand> target,
                    ReadableTransactionState state,
                    StorageStatement storageStatement,
                    ResourceLocker locks,
                    long lastTransactionIdWhenStarted)
             throws org.neo4j.kernel.api.exceptions.TransactionFailureException,
                    org.neo4j.kernel.api.exceptions.schema.CreateConstraintFailureException,
                    org.neo4j.kernel.api.exceptions.schema.ConstraintValidationKernelException

Generates a list of commands representing the changes in the given transaction state (state and legacyIndexTransactionState. The returned commands can be used to form CommandsToApply batches, which can be applied to this storage using apply(CommandsToApply, TransactionApplicationMode). The reason this is separated like this is that the generated commands can be used for other things than applying to storage, f.ex replicating to another storage engine.

Parameters:

target - Collection to put commands into.

state - ReadableTransactionState representing logical store changes to generate commands for.

storageStatement - StorageStatement to use for reading store state during creation of commands.

locks - ResourceLocker can grab additional locks. This locks client still have the potential to acquire more locks at this point. TODO we should try to get rid of this locking mechanism during creation of commands The reason it's needed is that some relationship changes in the record storage engine needs to lock prev/next relationships and these changes happens when creating commands The EntityLocker interface is a subset of Locks.Client interface, just to fit in while it's here.

lastTransactionIdWhenStarted - transaction id which was seen as last committed when this transaction started, i.e. before any changes were made and before any data was read. TODO Transitional (Collection), might be Stream or whatever.

Throws:

org.neo4j.kernel.api.exceptions.TransactionFailureException - if command generation fails or some prerequisite of some command didn't validate, for example if trying to delete a node that still has relationships.

org.neo4j.kernel.api.exceptions.schema.CreateConstraintFailureException - if this transaction was set to create a constraint and that failed.

org.neo4j.kernel.api.exceptions.schema.ConstraintValidationKernelException - if this transaction was set to create a constraint and some data violates that constraint.

apply

void apply(CommandsToApply batch,
           TransactionApplicationMode mode)
    throws Exception

Apply a batch of groups of commands to this storage.

Parameters:

batch - batch of groups of commands to apply to storage.

mode - TransactionApplicationMode when applying.

Throws:

Exception - if an error occurs during application.

commandReaderFactory

CommandReaderFactory commandReaderFactory()

Returns:

a CommandReaderFactory capable of returning commands readers for specific log entry versions.

flushAndForce

void flushAndForce(org.neo4j.io.pagecache.IOLimiter limiter)

Flushes and forces all changes down to underlying storage. This is a blocking call and when it returns all changes applied to this storage engine will be durable.

Parameters:

limiter - The IOLimiter used to moderate the rate of IO caused by the flush process.

registerDiagnostics

void registerDiagnostics(org.neo4j.kernel.info.DiagnosticsManager diagnosticsManager)

Registers diagnostics about the storage onto DiagnosticsManager.

Parameters:

diagnosticsManager - DiagnosticsManager to register diagnostics at.

forceClose

void forceClose()

Force close all opened resources. This may be called during startup if there's a failure during recovery or similar.

prepareForRecoveryRequired

void prepareForRecoveryRequired()

Startup process have reached the conclusion that recovery is required. Make the necessary preparations to be ready for recovering transactions.

loadSchemaCache

@Deprecated
void loadSchemaCache()

Deprecated.