Class RemoveFileOperation

java.lang.Object
org.apache.derby.impl.store.raw.data.RemoveFileOperation
All Implemented Interfaces:
Externalizable, Serializable, Formatable, TypedFormat, Loggable, Undoable

public class RemoveFileOperation extends Object implements Undoable
See Also:
  • Field Details

    • name

      private String name
    • generationId

      private long generationId
    • removeAtOnce

      private boolean removeAtOnce
    • fileToGo

      private transient StorageFile fileToGo
  • Constructor Details

    • RemoveFileOperation

      public RemoveFileOperation()
    • RemoveFileOperation

      RemoveFileOperation(String name, long generationId, boolean removeAtOnce)
  • Method Details

    • writeExternal

      public void writeExternal(ObjectOutput out) throws IOException
      Specified by:
      writeExternal in interface Externalizable
      Throws:
      IOException
    • readExternal

      public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException
      Specified by:
      readExternal in interface Externalizable
      Throws:
      IOException
      ClassNotFoundException
    • getTypeFormatId

      public int getTypeFormatId()
      Return my format identifier.
      Specified by:
      getTypeFormatId in interface TypedFormat
      Returns:
      The identifier. (A UUID stuffed in an array of 16 bytes).
    • getPreparedLog

      public ByteArray getPreparedLog()
      the default for prepared log is always null for all the operations that don't have optionalData. If an operation has optional data, the operation need to prepare the optional data for this method. Space Operation has no optional data to write out
      Specified by:
      getPreparedLog in interface Loggable
    • releaseResource

      public void releaseResource(Transaction tran)
      Description copied from interface: Loggable
      Release any resource that was acquired for doMe for rollback or recovery redo. This resource is acquired in either generateUndo (if this is a compensation operation during run time rollback or recovery rollback) or in needsRedo (if this is during recovery redo). The run time transaction context should have all the resource already acquird for run time roll forward, so there is no need to releaseResource during run time roll forward. This method must be safe to be called multiple times.
      Specified by:
      releaseResource in interface Loggable
    • group

      public int group()
      A space operation is a RAWSTORE log record
      Specified by:
      group in interface Loggable
    • doMe

      public void doMe(Transaction xact, LogInstant instant, LimitObjectInput in) throws StandardException
      Description copied from interface: Loggable
      Apply the change indicated by this operation and optional data. If this method fail, the system will be shut down because the log record has already been written to disk. Moreover, the log record will be replayed during recovery and this doMe method will be called on the same page again, so if it fails again, recovery will fail and the database cannot be started. So it is very important to make sure that every resource you need, such as disk space, has been acquired before the logAndDo method is called!
      This method cannot acquire any resource (like latching of a page) since it is called underneath the logging system, ie., the log record has already been written to the log stream.

      The available() method of in indicates how much data can be read, i.e. how much was originally written.

      Specified by:
      doMe in interface Loggable
      Parameters:
      xact - the Transaction
      instant - the log instant of this operation
      in - optional data
      Throws:
      StandardException - Standard Derby policy.
    • needsRedo

      public boolean needsRedo(Transaction xact) throws StandardException
      Description copied from interface: Loggable
      Determine if the operation should be reapplied in recovery redo. If redo is needed, acquire any resource that is necessary for the loggable's doMe method. These need to be released in the releaseResource method.

      The sequence of events in recovery redo of a Loggable operation is:

    • Get the loggable operation. If loggable.needsRedo is false, then no need to redo this operation.
    • If loggable.needsRedo is true, all the resources necessary for applying the doMe is acquired in needsRedo.
    • If the loggable is actually a compensation operation, then the logging system will find the undoable operation that needs to be undone, call compensation.setUndoOp with the undoable operation.
    • The recovery system then calls loggable.doMe, which re-applies the loggable operation, or re-applies the compensation operation
    • The recovery system then calls loggable.releaseResource.
    • Specified by:
      needsRedo in interface Loggable
      Parameters:
      xact - The transaction trying to redo this operation
      Returns:
      true if operation needs redoing, false if not.
      Throws:
      StandardException - Standard Derby error policy
      See Also:
    • generateUndo

      public Compensation generateUndo(Transaction xact, LimitObjectInput in) throws StandardException, IOException
      Description copied from interface: Undoable
      Generate a loggable which will undo this change, using the optional input if necessary.

      NOTE
      Any logical undo logic must be hidden behind generateUndo. During recovery redo, it should not depend on any logical undo logic.

      There are 3 ways to implement a redo-only log record:

    • Make the log record a Loggable instead of an Undoable, this is the cleanest method.
    • If you want to extend a log operation class that is an Undoable, you can then either have generateUndo return null - this is preferred - (the log operation's undoMe should never be called, so you can put a null body there if the super class you are extending does not implement a undoMe).
    • Or, have undoMe do nothing - this is least preferred.

      Any resource (e.g., latched page) that is needed for the undoable.undoMe() must be acquired in undoable.generateUndo(). Moreover, that resource must be identified in the compensation operation, and reacquired in the compensation.needsRedo() method during recovery redo.
      If you do write your own generateUndo or needsRedo, any resource you latch or acquire, you must release them in Compensation.doMe() or in Compensation.releaseResource().

      To write a generateUndo operation, find the object that needs to be rolled back. Assuming that it is a page, latch it, put together a Compensation operation with the undoOp set to this operation, and save the page number in the compensation operation, then return the Compensation operation to the logging system.

      The sequence of events in a rollback of a undoable operation is

    • The logging system calls undoable.generateUndo. If this returns null, then there is nothing to undo.
    • If generateUndo returns a Compensation operation, then the logging system will log the Compensation log record and call Compenstation.doMe(). (Hopefully, this just calls the undoable's undoMe)
    • After the Compensation operation has been applied, the logging system will call compensation.releaseResource(). If you do overwrite a super class's releaseResource(), it would be prudent to call super.releaseResource() first.

      The available() method of in indicates how much data can be read, i.e. how much was originally written.

    • Specified by:
      generateUndo in interface Undoable
      Parameters:
      xact - the transaction doing the rollback
      Returns:
      the compensation operation that will rollback this change, or null if nothing to undo.
      Throws:
      StandardException - Standard Derby policy.
      IOException - Can be thrown by any of the methods of ObjectInput.
      See Also: