org.eclipse.rdf4j.sail.memory

## Class MemoryStore

- java.lang.Object
- - org.eclipse.rdf4j.sail.helpers.AbstractSail
  - - org.eclipse.rdf4j.sail.helpers.AbstractNotifyingSail
    - - org.eclipse.rdf4j.sail.memory.MemoryStore

- All Implemented Interfaces:
    FederatedServiceResolverClient, NotifyingSail, Sail

      public class MemoryStore
      extends AbstractNotifyingSail
      implements FederatedServiceResolverClient

  An implementation of the Sail interface that stores its data in main memory and that can use a file for persistent storage. This Sail implementation supports single, isolated transactions. This means that changes to the data are not visible until a transaction is committed and that concurrent transactions are not possible. When another transaction is active, calls to `startTransaction()` will block until the active transaction is committed or rolled back. The MemoryStore is designed for datasets with fewer than 100,000 triples. The MemoryStore uses hash tables, and when these hash tables fill up it copies the values to larger hash tables. This can cause strain on the garbage collector due to lots of memory being allocated and freed.
  Author:
    Arjohn Kampman, jeen

- - ### Field Summary

    Fields
    Modifier and Type | Field and Description
    --- | ---
    `protected static String` | `DATA_FILE_NAME`
    `protected static String` | `SYNC_FILE_NAME`

    - ### Fields inherited from class org.eclipse.rdf4j.sail.helpers.AbstractSail

      `connectionTimeOut, DEFAULT_CONNECTION_TIMEOUT, DEFAULT_ITERATION_SYNC_THRESHOLD, initializationLock`

  - ### Constructor Summary

    Constructors
    Constructor and Description
    `MemoryStore()` Creates a new MemoryStore.
    `MemoryStore(File dataDir)` Creates a new persistent MemoryStore.

  - ### Method Summary

    All Methods Instance Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `protected void` | `cancelSyncTask()`
    `protected void` | `cancelSyncTimer()`
    `protected NotifyingSailConnection` | `getConnectionInternal()` Returns a store-specific SailConnection object.
    `EvaluationStrategyFactory` | `getEvaluationStrategyFactory()`
    `FederatedServiceResolver` | `getFederatedServiceResolver()`
    `boolean` | `getPersist()`
    `long` | `getSyncDelay()` Gets the currently configured sync delay.
    `ValueFactory` | `getValueFactory()` Gets a ValueFactory object that can be used to create IRI-, blank node-, literal- and statement objects.
    `protected void` | `initializeInternal()` Initializes this repository.
    `boolean` | `isWritable()` Checks whether this Sail object is writable.
    `void` | `notifySailChanged(SailChangedEvent event)` Notifies all registered SailChangedListener's of changes to the contents of this Sail.
    `protected void` | `scheduleSyncTask()`
    `void` | `setEvaluationStrategyFactory(EvaluationStrategyFactory factory)` Sets the `EvaluationStrategy` to use.
    `void` | `setFederatedServiceResolver(FederatedServiceResolver resolver)` Overrides the `FederatedServiceResolver` used by this instance, but the given resolver is not shutDown when this instance is.
    `void` | `setPersist(boolean persist)`
    `void` | `setSyncDelay(long syncDelay)` Sets the time (in milliseconds) to wait after a transaction was commited before writing the changed data to file.
    `protected void` | `shutDownInternal()` Do store-specific operations to ensure proper shutdown of the store.
    `void` | `sync()` Synchronizes the contents of this repository with the data that is stored on disk.

    - ### Methods inherited from class org.eclipse.rdf4j.sail.helpers.AbstractNotifyingSail

      `addSailChangedListener, getConnection, removeSailChangedListener`

    - ### Methods inherited from class org.eclipse.rdf4j.sail.helpers.AbstractSail

      `addSupportedIsolationLevel, connectionClosed, debugEnabled, getDataDir, getDefaultIsolationLevel, getIterationCacheSyncThreshold, getSupportedIsolationLevels, init, initialize, isInitialized, isTrackResultSize, removeSupportedIsolationLevel, setConnectionTimeOut, setDataDir, setDefaultIsolationLevel, setIterationCacheSyncThreshold, setSupportedIsolationLevels, setSupportedIsolationLevels, setTrackResultSize, shutDown, toString`

    - ### Methods inherited from class java.lang.Object

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

    - ### Methods inherited from interface org.eclipse.rdf4j.sail.Sail

      `getDataDir, getDefaultIsolationLevel, getSupportedIsolationLevels, init, initialize, setDataDir, shutDown`

- - ### Field Detail

    - #### DATA_FILE_NAME

          protected static final String DATA_FILE_NAME

      See Also:
        Constant Field Values

    - #### SYNC_FILE_NAME

          protected static final String SYNC_FILE_NAME

      See Also:
        Constant Field Values

  - ### Constructor Detail

    - #### MemoryStore

          public MemoryStore()

      Creates a new MemoryStore.

    - #### MemoryStore

          public MemoryStore(File dataDir)

      Creates a new persistent MemoryStore. If the specified data directory contains an existing store, its contents will be restored upon initialization.
      Parameters:
        `dataDir` - the data directory to be used for persistence.

  - ### Method Detail

    - #### setPersist

          public void setPersist(boolean persist)

    - #### getPersist

          public boolean getPersist()

    - #### setSyncDelay

          public void setSyncDelay(long syncDelay)

      Sets the time (in milliseconds) to wait after a transaction was commited before writing the changed data to file. Setting this variable to 0 will force a file sync immediately after each commit. A negative value will deactivate file synchronization until the Sail is shut down. A positive value will postpone the synchronization for at least that amount of milliseconds. If in the meantime a new transaction is started, the file synchronization will be rescheduled to wait for another `syncDelay` ms. This way, bursts of transaction events can be combined in one file sync.

      The default value for this parameter is `0` (immediate synchronization).

      Parameters:
        `syncDelay` - The sync delay in milliseconds.

    - #### getSyncDelay

          public long getSyncDelay()

      Gets the currently configured sync delay.
      Returns:
        syncDelay The sync delay in milliseconds.
      See Also:
        `setSyncDelay(long)`

    - #### getEvaluationStrategyFactory

          public EvaluationStrategyFactory getEvaluationStrategyFactory()

      Returns:
        Returns the `EvaluationStrategy`.

    - #### setEvaluationStrategyFactory

          public void setEvaluationStrategyFactory(EvaluationStrategyFactory factory)

      Sets the `EvaluationStrategy` to use.

    - #### getFederatedServiceResolver

          public FederatedServiceResolver getFederatedServiceResolver()

      Returns:
        Returns the SERVICE resolver.

    - #### setFederatedServiceResolver

          public void setFederatedServiceResolver(FederatedServiceResolver resolver)

      Overrides the `FederatedServiceResolver` used by this instance, but the given resolver is not shutDown when this instance is.
      Specified by:
        `setFederatedServiceResolver` in interface `FederatedServiceResolverClient`
      Parameters:
        `resolver` - The SERVICE resolver to set.

    - #### initializeInternal

          protected void initializeInternal()
                                     throws SailException

      Initializes this repository. If a persistence file is defined for the store, the contents will be restored.
      Overrides:
        `initializeInternal` in class `AbstractSail`
      Throws:
        `SailException` - when initialization of the store failed.

    - #### shutDownInternal

          protected void shutDownInternal()
                                   throws SailException

      Description copied from class: `AbstractSail`
      Do store-specific operations to ensure proper shutdown of the store.
      Specified by:
        `shutDownInternal` in class `AbstractSail`
      Throws:
        `SailException`

    - #### isWritable

          public boolean isWritable()

      Checks whether this Sail object is writable. A MemoryStore is not writable if a read-only data file is used.
      Specified by:
        `isWritable` in interface `Sail`

    - #### getConnectionInternal

          protected NotifyingSailConnection getConnectionInternal()
                                                           throws SailException

      Description copied from class: `AbstractSail`
      Returns a store-specific SailConnection object.
      Specified by:
        `getConnectionInternal` in class `AbstractNotifyingSail`
      Returns:
        A connection to the store.
      Throws:
        `SailException`

    - #### getValueFactory

          public ValueFactory getValueFactory()

      Description copied from interface: `Sail`
      Gets a ValueFactory object that can be used to create IRI-, blank node-, literal- and statement objects.
      Specified by:
        `getValueFactory` in interface `Sail`
      Returns:
        a ValueFactory object for this Sail object.

    - #### notifySailChanged

          public void notifySailChanged(SailChangedEvent event)

      Description copied from class: `AbstractNotifyingSail`
      Notifies all registered SailChangedListener's of changes to the contents of this Sail.
      Overrides:
        `notifySailChanged` in class `AbstractNotifyingSail`

    - #### scheduleSyncTask

          protected void scheduleSyncTask()
                                   throws SailException

      Throws:
        `SailException`

    - #### cancelSyncTask

          protected void cancelSyncTask()

    - #### cancelSyncTimer

          protected void cancelSyncTimer()

    - #### sync

          public void sync()
                    throws SailException

      Synchronizes the contents of this repository with the data that is stored on disk. Data will only be written when the contents of the repository and data in the file are out of sync.
      Throws:
        `SailException`

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