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org.apache.derby.impl.store.raw.data
Class AllocPage  

java.lang.Object
  org.apache.derby.impl.store.raw.data.BasePage
      org.apache.derby.impl.store.raw.data.CachedPage
          org.apache.derby.impl.store.raw.data.StoredPage
              org.apache.derby.impl.store.raw.data.AllocPage

All Implemented Interfaces:

org.apache.derby.iapi.services.cache.Cacheable, org.apache.derby.iapi.services.locks.Lockable, java.util.Observer, org.apache.derby.iapi.store.raw.Page, org.apache.derby.iapi.services.io.TypedFormat

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public class AllocPage

extends StoredPage

An allocation page of the file container.

This class extends a normal Stored page, with the exception that a hunk of space may be 'borrowed' by the file container to store the file header.

The borrowed space is not visible to the alloc page even though it is present in the page data array. It is accessed directly by the FileContainer. Any change made to the borrowed space is not managed or seen by the allocation page.

Page Format
An allocation page extends a stored page, the on disk format is different from a stored page in that N bytes are 'borrowed' by the container and the page header of an allocation page will be slightly bigger than a normal stored page. This N bytes are stored between the page header and the record space.

The reason why this N bytes can't simply be a row is because it needs to be statically accessible by the container object to avoid a chicken and egg problem of the container object needing to instantiate an alloc page object before it can be objectified, and an alloc page object needing to instantiate a container object before it can be objectified. So this N bytes must be stored outside of the normal record interface yet it must be settable because only the first alloc page has this borrowed space. Other (non-first) alloc page have N == 0.

                             <-- borrowed ->
        +----------+-------------+---+---------+-------------------+-------------+--------+
        | FormatId | page header | N | N bytes | alloc extend rows | slot offset |checksum|
        +----------+-------------+---+---------+-------------------+-------------+--------+
        

N is a byte that indicates the size of the borrowed space. Once an alloc page is initialized, the value of N cannot change.

The maximum space that can be borrowed by the container is 256 bytes.

The allocation page are of the same page size as any other pages in the container. The first allocation page of the FileContainer starts at the first physical byte of the container. Subsequent allocation pages are chained via the nextAllocPageOffset. Each allocation page is expected to manage at least 1000 user pages (for 1K page size) so this chaining may not be a severe performance hit. The logical -> physical mapping of an allocation page is stored in the previous allocation page. The container object will need to maintain this mapping.

The following fields are stored in the page header

Field Summary



protected static int
ALLOC_PAGE_HEADER_OFFSET



          constants



protected static int
ALLOC_PAGE_HEADER_SIZE



           



protected static int
BORROWED_SPACE_LEN



           



protected static int
BORROWED_SPACE_OFFSET



           



private  int
borrowedSpace



           



private  AllocExtent
extent



           



static int
FORMAT_NUMBER



           



protected static int
MAX_BORROWED_SPACE



           



private  long
nextAllocPageNumber



          alloc page header



private  long
nextAllocPageOffset



           



private  long
reserved1



           



private  long
reserved2



           



private  long
reserved3



           



private  long
reserved4



           



static java.lang.String
TEST_MULTIPLE_ALLOC_PAGE



          Extent Testing

 Use these strings to simulate error conditions for
 testing purposes.


 


Fields inherited from class org.apache.derby.impl.store.raw.data.StoredPage


bh, CHECKSUM_SIZE, COLUMN_FIRST, COLUMN_LONG, COLUMN_NONE, freeSpace, LARGE_SLOT_SIZE, logicalDataOut, maxFieldSize, minimumRecordSize, OVERFLOW_POINTER_SIZE, OVERFLOW_PTR_FIELD_SIZE, PAGE_HEADER_OFFSET, PAGE_HEADER_SIZE, PAGE_VERSION_OFFSET, rawDataIn, rawDataOut, RECORD_SPACE_OFFSET, SMALL_SLOT_SIZE, spareSpace, totalSpace


 


Fields inherited from class org.apache.derby.impl.store.raw.data.CachedPage


alreadyReadPage, containerCache, dataFactory, initialRowCount, isDirty, PAGE_FORMAT_ID_SIZE, pageCache, pageData, preDirty, WRITE_NO_SYNC, WRITE_SYNC


 


Fields inherited from class org.apache.derby.impl.store.raw.data.BasePage


identity, inClean, INIT_PAGE_OVERFLOW, INIT_PAGE_REUSE, INIT_PAGE_REUSE_RECORDID, INVALID_PAGE, LOG_RECORD_DEFAULT, LOG_RECORD_FOR_PURGE, LOG_RECORD_FOR_UPDATE, owner, preLatch, VALID_PAGE


 


Fields inherited from interface org.apache.derby.iapi.store.raw.Page


DIAG_BYTES_FREE, DIAG_BYTES_RESERVED, DIAG_MAXROWSIZE, DIAG_MINIMUM_REC_SIZE, DIAG_MINROWSIZE, DIAG_NUMOVERFLOWED, DIAG_PAGE_SIZE, DIAG_PAGEOVERHEAD, DIAG_RESERVED_SPACE, DIAG_ROWSIZE, DIAG_SLOTTABLE_SIZE, FIRST_SLOT_NUMBER, INSERT_CONDITIONAL, INSERT_DEFAULT, INSERT_FOR_SPLIT, INSERT_INITIAL, INSERT_OVERFLOW, INSERT_UNDO_WITH_PURGE, INVALID_SLOT_NUMBER


 






Constructor Summary


AllocPage()



           


 






Method Summary



 void
addPage(FileContainer mycontainer,
        long newPageNumber,
        org.apache.derby.iapi.store.raw.xact.RawTransaction ntt,
        BaseContainerHandle userHandle)



          Add a page which is managed by this alloc page.



 boolean
canAddFreePage(long lastAllocatedPage)



           



 void
chainNewAllocPage(BaseContainerHandle allocHandle,
                  long newAllocPageNum,
                  long newAllocPageOffset)



           



protected  void
chainNextAllocPage(org.apache.derby.iapi.store.raw.log.LogInstant instant,
                   long newAllocPageNum,
                   long newAllocPageOffset)



          Chain the next page number and offset underneath a log record



protected  boolean
compress(org.apache.derby.iapi.store.raw.xact.RawTransaction ntt,
         FileContainer myContainer)



          compress out empty pages at end of container.



protected  void
compressSpace(org.apache.derby.iapi.store.raw.log.LogInstant instant,
              int new_highest_page,
              int num_pages_truncated)



          Compress free pages.



private  AllocExtent
createExtent(long pageNum,
             int pageSize,
             int pagesAlloced,
             int availspace)



           



protected  void
createPage(org.apache.derby.iapi.store.raw.PageKey newIdentity,
           int[] args)



          Create a new alloc page.



 void
deallocatePage(BaseContainerHandle userHandle,
               long pageNumber)



           



protected  AllocExtent
getAllocExtent()



          Return a copy of the allocExtent to be cached by the container.



 long
getLastPagenum()



           



protected  long
getLastPreallocPagenum()



           



protected  int
getMaxFreeSpace()



          The maximum free space on this page possible.



 long
getMaxPagenum()



           



 long
getNextAllocPageNumber()



           



 long
getNextAllocPageOffset()



           



protected  int
getPageStatus(long pageNumber)



           



 int
getTypeFormatId()



          Return my format identifier.



protected  void
initFromData(FileContainer myContainer,
             org.apache.derby.iapi.store.raw.PageKey newIdentity)



          Initialize in memory structure using the buffer in pageData



 boolean
isLast()



           



 long
nextFreePageNumber(long pnum)



          Return the next free page number after given page number



protected  void
preAllocatePage(FileContainer myContainer,
                int preAllocThreshold,
                int preAllocSize)



          Preallocate user page if needed.



private  void
readAllocPageHeader()



           



static void
ReadContainerInfo(byte[] containerInfo,
                  byte[] epage)



          Extract the container information from epage.



private  AllocExtent
readExtent(int offset)



           



protected  void
setPageStatus(org.apache.derby.iapi.store.raw.log.LogInstant instant,
              long pageNumber,
              int newStatus)



          Do the actual page allocation/deallocation/ree underneath a log operation.



 java.lang.String
toString()



          debugging, print this page



protected  void
undoCompressSpace(org.apache.derby.iapi.store.raw.log.LogInstant instant,
                  int new_highest_page,
                  int num_pages_truncated)



          Handle undo of compress space operation.



private  void
updateAllocPageHeader()



           



protected  void
updateUnfilledPageInfo(AllocExtent inputExtent)



           



static void
WriteContainerInfo(byte[] containerInfo,
                   byte[] epage,
                   boolean create)



          Write the container information into the container information area.



private  void
writeExtent(int offset)



           



protected  void
writePage(org.apache.derby.iapi.store.raw.PageKey identity)



          Write the page out


 


Methods inherited from class org.apache.derby.impl.store.raw.data.StoredPage


allowInsert, appendOverflowFieldHeader, clearSection, compactRecord, currentTimeStamp, doUpdateAtSlot, entireRecordOnPage, equalTimeStamp, expandPage, fetchNumFieldsAtSlot, getCurrentFreeSpace, getIsOverflow, getNewOverflowPage, getOverflowPage, getOverflowPageForInsert, getOverflowPageForInsert, getOverflowSlot, getPageSize, getRecordLength, getRecordPortionLength, getReservedCount, getSlotsInUse, getTotalSpace, initialize, initPage, insertAtSlot, internalDeletedRecordCount, isOverflowPage, logAction, logColumn, logField, logLongColumn, logRecord, logRow, moveRecordForCompressAtSlot, newRecordId, newRecordId, newRecordIdAndBump, purgeOverflowAtSlot, purgeRecord, purgeRowPieces, recordHeaderOnDemand, releaseExclusive, removeOrphanedColumnChain, reserveSpaceForSlot, restorePortionLongColumn, restoreRecordFromSlot, restoreRecordFromStream, setDeleteStatus, setPageStatus, setReservedSpace, setTimeStamp, skipField, skipRecord, spaceForCopy, spaceForCopy, spaceForInsert, spaceForInsert, storeField, storeRecord, unfilled, updateChecksum, updateFieldAtSlot, updateFieldOverflowDetails, updateOverflowDetails, updateOverflowed, usePageBuffer, validateChecksum, writeFormatId


 


Methods inherited from class org.apache.derby.impl.store.raw.data.CachedPage


clean, clearIdentity, createIdentity, isActuallyDirty, isDirty, preDirty, setContainerRowCount, setDirty, setFactory, setIdentity, setPageArray


 


Methods inherited from class org.apache.derby.impl.store.raw.data.BasePage


bumpPageVersion, bumpRecordCount, cleanPageForReuse, clearLastLogInstant, compactRecord, copyAndPurge, deallocatePage, delete, deleteAtSlot, fetch, fetchFieldFromSlot, fetchFromSlot, fetchNumFields, fillInIdentity, findRecordById, getAuxObject, getHeaderAtSlot, getIdentity, getInvalidRecordHandle, getLastLogInstant, getNextSlotNumber, getPageId, getPageNumber, getPageStatus, getPageVersion, getRecordHandle, getRecordHandleAtSlot, getSlotNumber, initializeHeaders, initPage, insert, insertAllowOverflow, insertLongColumn, insertNoOverflow, internalNonDeletedRecordCount, isDeletedAtSlot, isDeletedOnPage, isLatched, lockAttributes, lockerAlwaysCompatible, lockEvent, makeRecordHandle, MakeRecordHandle, nonDeletedRecordCount, purgeAtSlot, recordCount, recordExists, removeAndShiftDown, requestCompatible, setAuxObject, setDeleteStatus, setExclusive, setExclusiveNoWait, setHeaderAtSlot, setPageStatus, setPageVersion, shiftUp, slotTableToString, unlatch, unlockEvent, update, update, updateAtSlot, updateLastLogInstant


 


Methods inherited from class java.lang.Object


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


 


Methods inherited from interface org.apache.derby.iapi.services.cache.Cacheable


getIdentity


 








Field Detail




FORMAT_NUMBER
public static final int FORMAT_NUMBER


See Also:
Constant Field Values




nextAllocPageNumber
private long nextAllocPageNumber

alloc page header







nextAllocPageOffset
private long nextAllocPageOffset







reserved1
private long reserved1







reserved2
private long reserved2







reserved3
private long reserved3







reserved4
private long reserved4







extent
private AllocExtent extent







borrowedSpace
private int borrowedSpace







ALLOC_PAGE_HEADER_OFFSET
protected static final int ALLOC_PAGE_HEADER_OFFSET

constants


See Also:
Constant Field Values




ALLOC_PAGE_HEADER_SIZE
protected static final int ALLOC_PAGE_HEADER_SIZE


See Also:
Constant Field Values




BORROWED_SPACE_OFFSET
protected static final int BORROWED_SPACE_OFFSET


See Also:
Constant Field Values




BORROWED_SPACE_LEN
protected static final int BORROWED_SPACE_LEN


See Also:
Constant Field Values




MAX_BORROWED_SPACE
protected static final int MAX_BORROWED_SPACE


See Also:
Constant Field Values




TEST_MULTIPLE_ALLOC_PAGE
public static final java.lang.String TEST_MULTIPLE_ALLOC_PAGE

Extent Testing

 Use these strings to simulate error conditions for
 testing purposes.











Constructor Detail




AllocPage
public AllocPage()









Method Detail




getTypeFormatId
public int getTypeFormatId()

Return my format identifier.


Specified by:
getTypeFormatId in interface org.apache.derby.iapi.services.io.TypedFormat
Overrides:
getTypeFormatId in class StoredPage








getMaxFreeSpace
protected int getMaxFreeSpace()

Description copied from class: StoredPage
The maximum free space on this page possible.
 

 The the maximum amount of space that can be used on the page
 for the records and the slot offset table.
 NOTE: subclass may have overwitten it to report less freeSpace


Overrides:
getMaxFreeSpace in class StoredPage








createPage
protected void createPage(org.apache.derby.iapi.store.raw.PageKey newIdentity,
                          int[] args)
                   throws org.apache.derby.iapi.error.StandardException

Create a new alloc page.


Overrides:
createPage in class StoredPage








createExtent
private AllocExtent createExtent(long pageNum,
                                 int pageSize,
                                 int pagesAlloced,
                                 int availspace)








initFromData
protected void initFromData(FileContainer myContainer,
                            org.apache.derby.iapi.store.raw.PageKey newIdentity)
                     throws org.apache.derby.iapi.error.StandardException

Initialize in memory structure using the buffer in pageData


Overrides:
initFromData in class StoredPage








writePage
protected void writePage(org.apache.derby.iapi.store.raw.PageKey identity)
                  throws org.apache.derby.iapi.error.StandardException

Write the page out


Overrides:
writePage in class StoredPage








readAllocPageHeader
private void readAllocPageHeader()
                          throws java.io.IOException








updateAllocPageHeader
private void updateAllocPageHeader()
                            throws java.io.IOException








readExtent
private AllocExtent readExtent(int offset)
                        throws java.io.IOException,
                               java.lang.ClassNotFoundException








writeExtent
private void writeExtent(int offset)
                  throws java.io.IOException








WriteContainerInfo
public static void WriteContainerInfo(byte[] containerInfo,
                                      byte[] epage,
                                      boolean create)
                               throws org.apache.derby.iapi.error.StandardException

Write the container information into the container information area.








ReadContainerInfo
public static void ReadContainerInfo(byte[] containerInfo,
                                     byte[] epage)

Extract the container information from epage.








nextFreePageNumber
public long nextFreePageNumber(long pnum)

Return the next free page number after given page number








addPage
public void addPage(FileContainer mycontainer,
                    long newPageNumber,
                    org.apache.derby.iapi.store.raw.xact.RawTransaction ntt,
                    BaseContainerHandle userHandle)
             throws org.apache.derby.iapi.error.StandardException

Add a page which is managed by this alloc page.
                Return the page number of the newly added page.

                
 MT - thread aware (latched)








deallocatePage
public void deallocatePage(BaseContainerHandle userHandle,
                           long pageNumber)
                    throws org.apache.derby.iapi.error.StandardException








updateUnfilledPageInfo
protected void updateUnfilledPageInfo(AllocExtent inputExtent)








canAddFreePage
public boolean canAddFreePage(long lastAllocatedPage)








getNextAllocPageOffset
public long getNextAllocPageOffset()








chainNewAllocPage
public void chainNewAllocPage(BaseContainerHandle allocHandle,
                              long newAllocPageNum,
                              long newAllocPageOffset)
                       throws org.apache.derby.iapi.error.StandardException








getNextAllocPageNumber
public long getNextAllocPageNumber()








isLast
public boolean isLast()








getLastPagenum
public long getLastPagenum()








getMaxPagenum
public long getMaxPagenum()








getLastPreallocPagenum
protected long getLastPreallocPagenum()








getPageStatus
protected int getPageStatus(long pageNumber)








setPageStatus
protected void setPageStatus(org.apache.derby.iapi.store.raw.log.LogInstant instant,
                             long pageNumber,
                             int newStatus)
                      throws org.apache.derby.iapi.error.StandardException

Do the actual page allocation/deallocation/ree underneath a log operation.
                Change the page status to new status








chainNextAllocPage
protected void chainNextAllocPage(org.apache.derby.iapi.store.raw.log.LogInstant instant,
                                  long newAllocPageNum,
                                  long newAllocPageOffset)
                           throws org.apache.derby.iapi.error.StandardException

Chain the next page number and offset underneath a log record








compressSpace
protected void compressSpace(org.apache.derby.iapi.store.raw.log.LogInstant instant,
                             int new_highest_page,
                             int num_pages_truncated)
                      throws org.apache.derby.iapi.error.StandardException

Compress free pages.
 

 Compress the free pages at the end of the range maintained by
 this allocation page.  All pages being compressed should be FREE.
 Only pages in the last allocation page can be compressed.
 









undoCompressSpace
protected void undoCompressSpace(org.apache.derby.iapi.store.raw.log.LogInstant instant,
                                 int new_highest_page,
                                 int num_pages_truncated)
                          throws org.apache.derby.iapi.error.StandardException

Handle undo of compress space operation.








toString
public java.lang.String toString()

Description copied from class: StoredPage
debugging, print this page


Overrides:
toString in class StoredPage








getAllocExtent
protected AllocExtent getAllocExtent()

Return a copy of the allocExtent to be cached by the container.
                the container must take care to maintain its coherency by
                invalidating the cache before any update.








preAllocatePage
protected void preAllocatePage(FileContainer myContainer,
                               int preAllocThreshold,
                               int preAllocSize)

Preallocate user page if needed.








compress
protected boolean compress(org.apache.derby.iapi.store.raw.xact.RawTransaction ntt,
                           FileContainer myContainer)
                    throws org.apache.derby.iapi.error.StandardException

compress out empty pages at end of container.
 

 Call the extent to update the data structure make the bit map look
 like contiguous free pages at the end of the extent no longer exist.
 Similar to preallocate do the operation unlogged, need to force the
 change to the extent before actually removing the space from the
 file.
 

 The sequence is:
     1) update extent data structure
     2) force extent changes to disk
     3) truncate pages

 If the system crashes between 1 and 2 then no changes are on disk.
 If the system crashes between 2 and 3 then there are extra pages in
     the file that extent does not know about, this is the same case
     as preallocation which the code already handes.  It will handle
     any set of pages from 0 to all of the intended pages being 
     truncated.  The next allocate looks at actual size of file as
     does the right thing.

 













  

  
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  SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD

DETAIL: FIELD | CONSTR | METHOD