B2IUndo (Apache Derby V10.14 Internals)

java.lang.Object
- org.apache.derby.impl.store.access.btree.index.B2IUndo

All Implemented Interfaces:

java.io.Externalizable, java.io.Serializable, Formatable, TypedFormat, LogicalUndo
```
public class B2IUndo
extends java.lang.Object
implements LogicalUndo, Formatable
```
The B2IUndo interface packages up the routines which the rawstore needs to call to perform logical undo of a record in a B2i. The rawstore will determine that a page has changed since the record was written, and if it has it will call the findUndo() interface, to find the page where the record exists (as it may have moved).
This class must not contain any persistent state, as this class is stored in the log record of the insert/delete.

See Also:

LogicalUndoable, Undoable.generateUndo(org.apache.derby.iapi.store.raw.Transaction, org.apache.derby.iapi.services.io.LimitObjectInput), Serialized Form

Constructor Summary

Constructors
Constructor Description

B2IUndo()

Constructors
Constructor	Description
`B2IUndo()`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method	Description
`Page`	`findUndo(Transaction rawtran, LogicalUndoable pageOp, LimitObjectInput in)`	Find the page and record to undo.
`int`	`getTypeFormatId()`	Return my format identifier.
`void`	`readExternal(java.io.ObjectInput in)`	Restore the in-memory representation from the stream.
`void`	`writeExternal(java.io.ObjectOutput out)`	This object has no state, so nothing to write.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - B2IUndo
```
public B2IUndo()
```
- Method Detail
  - findUndo
```
public Page findUndo(Transaction rawtran,
                     LogicalUndoable pageOp,
                     LimitObjectInput in)
              throws StandardException,
                     java.io.IOException
```
    Find the page and record to undo. If no logical undo is necessary, i.e., row has not moved, then just return the latched page where undo should go. If the record has moved, it has a new recordId on the new page, this routine needs to call pageOp.resetRecord with the new RecordHandle so that the logging system can update the compensation Operation with the new location.
    
    Specified by:
    
    findUndo in interface LogicalUndo
    
    Parameters:
    
    rawtran - the transaction doing the rollback
    
    pageOp - the page operation that supports logical undo. This LogicalUndo function pointer is a field of that pageOperation
    
    in - data stored in the log stream that contains the record data necessary to restore the row.
    
    Throws:
    
    StandardException - Standard Derby error policy
    
    java.io.IOException - Method may read from InputStream
  - 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).
    
    See Also:
    
    TypedFormat.getTypeFormatId()
  - writeExternal
```
public void writeExternal(java.io.ObjectOutput out)
                   throws java.io.IOException
```
    This object has no state, so nothing to write.
    
    Specified by:
    
    writeExternal in interface java.io.Externalizable
    
    Throws:
    
    java.io.IOException
  - readExternal
```
public void readExternal(java.io.ObjectInput in)
                  throws java.io.IOException,
                         java.lang.ClassNotFoundException
```
    Restore the in-memory representation from the stream. This object has no state, so nothing to restore.
    
    Specified by:
    
    readExternal in interface java.io.Externalizable
    
    Throws:
    
    java.lang.ClassNotFoundException - Thrown if the stored representation is serialized and a class named in the stream could not be found.
    
    java.io.IOException
    
    See Also:
    
    Externalizable.readExternal(java.io.ObjectInput)

Class B2IUndo

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

B2IUndo

Method Detail

findUndo

getTypeFormatId

writeExternal

readExternal