Examples of org.apache.derby.iapi.store.raw.Page

org.apache.derby.iapi.store.raw.Page
A Page contains an ordered set of records which are the stored form of rows. A record is a stream of bytes created from a row array. The record contains one or more fields, fields have a one to one correlation with the DataValueDescriptor's contained within a row array.
A Page represents exclusive access to a data page within a container. Exclusive access is released by calling the unlatch() method, once that occurs the caller must no longer use the Page reference.
Several of the methods in Page take a RecordHandle as an argument. RecordHandles are obtained from a Page, while holding exclusive access of Page or a from a previous exclusive access of a Page representing the same data page. All RecordHandle's used as arguments to methods (with the exception of recordExists()) must be valid for the current state of the page. If they are not valid then the method will throw an exception. A caller can ensure that a record handle is valid by:
- Obtaining the handle during this exclusive access of this page
- Checking the record still exists with the method recordExists()
- Not using a handle after a deleteAtSlot().
Several of the methods in Page take a slot number as an argument. A slot always correspond to a record, which may be deleted or undeleted.
MT - Latched - In general every method requires the page to be latched.
Latching
All page methods which are not valid for a latched page throw an exception if the page is not latched. [@exception clauses on all the methods should be updated to reflect this].
Aux Objects
The page cache will manage a client object along with the page as long as it remains in cache. This object is called the "aux object". The aux object is associated with the page with setAuxObject(), and can be retreived later with getAuxObject(). The aux object will remain valid as long as the page is latched, but callers cannot assume that an aux object will ever stick around once the page is unlatched. However, the page manager promises to call pageBeingEvicted() once before clearing the aux reference from the page. @see Object @see ContainerHandle @see RecordHandle @see AuxObject

            lastInsertedPage = new long[4];
            lastInsertedPage[0] = last;


            for (int i = 3; i > 0; i--)
            {
                Page page = addPage(handle, false);
                lastInsertedPage[i] = page.getPageNumber();
                page.unlatch();
            }
        }
    }

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    // create the first alloc page and the first user page, 
    // if this fails for any reason the transaction
    // will roll back and the container will be dropped (removed)
    ContainerHandle containerHdl = null;
    Page            firstPage    = null;


    try 
        {
      // if opening a temporary container with IS_KEPT flag set,
      // make sure to open it with IS_KEPT too.
      if (tmpContainer && 
        ((temporaryFlag & TransactionController.IS_KEPT) == 
                     TransactionController.IS_KEPT)) 
            {


        mode |= ContainerHandle.MODE_TEMP_IS_KEPT;
      }


      // open no-locking as we already have the container locked
      containerHdl = 
                t.openContainer(
                    identity, null, (ContainerHandle.MODE_FORUPDATE | mode)); 


      // we just added it, containerHdl should not be null
            if (SanityManager.DEBUG)
                SanityManager.ASSERT(containerHdl != null);


      if (!tmpContainer) 
            {
        // make it persistent (in concept if not in reality)
        RawContainerHandle rch = (RawContainerHandle)containerHdl;


        ContainerOperation lop = 
          new ContainerOperation(rch, ContainerOperation.CREATE);


        // mark the container as pre-dirtied so that if a checkpoint
        // happens after the log record is sent to the log stream, the
        // cache cleaning will wait for this change.
        rch.preDirty(true);
        try
        {
          t.logAndDo(lop);


          // flush the log to reduce the window between where
          // the container is created & synced and the log record
          // for it makes it to disk. If we fail in this
          // window we will leave a stranded container file.
          flush(t.getLastLogInstant());
        }
        finally
        {
          // in case logAndDo fail, make sure the container is not
          // stuck in preDirty state.
          rch.preDirty(false);
        }
      }


      firstPage = containerHdl.addPage();


    } 
        finally 
        {


      if (firstPage != null) 
            {
        firstPage.unlatch();
        firstPage = null;
      }
      
      containerCache.release(container);

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            DataValueDescriptor[] row = 
                runtime_mem.get_row_for_export(getRawTran());


            // Print pages of the heap.
            Page page = container.getFirstPage();


            while (page != null)
            {
                SanityManager.DEBUG_PRINT(
                    "p_heap", ConglomerateUtil.debugPage(page, 0, false, row));


                long pageid = page.getPageNumber();
                page.unlatch();
                page = container.getNextPage(pageid);
            }
        }


        return;

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            // Reposition to remembered spot on page.


            // Get the page object. If getPage() returns null, the page is
            // not valid (could for instance have been removed by compress
            // table) so we need to reposition by key instead.
            Page page = container.getPage(pos.current_rh.getPageNumber());
            if (page != null) {
                ControlRow row =
                        ControlRow.getControlRowForPage(container, page);
                if (row instanceof LeafControlRow &&
                        !row.page.isRepositionNeeded(pos.versionWhenSaved)) {

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     */
    void savePositionAndReleasePage(DataValueDescriptor[] partialKey,
                                    int[] vcols)
            throws StandardException {


        final Page page = scan_position.current_leaf.getPage();


        if (SanityManager.DEBUG) {
            SanityManager.ASSERT(page.isLatched(), "Page is not latched");
            SanityManager.ASSERT(scan_position.current_positionKey == null,
                                 "Scan position already saved");


            if (partialKey == null) {
                SanityManager.ASSERT(vcols == null);
            }
            if (vcols != null) {
                SanityManager.ASSERT(partialKey != null);
                SanityManager.ASSERT(vcols.length <= partialKey.length);
            }
        }


        try {
            DataValueDescriptor[] fullKey = scan_position.getKeyTemplate();


            FetchDescriptor fetchDescriptor = null;
            boolean haveAllColumns = false;
            if (partialKey != null) {
                int copiedCols = 0;
                final int partialKeyLength =
                        (vcols == null) ? partialKey.length : vcols.length;
                for (int i = 0; i < partialKeyLength; i++) {
                    if (vcols == null || vcols[i] != 0) {
                        fullKey[i].setValue(partialKey[i]);
                        copiedCols++;
                    }
                }
                if (copiedCols < fullKey.length) {
                    fetchDescriptor =
                            scan_position.getFetchDescriptorForSaveKey(
                            vcols, fullKey.length);
                } else {
                    haveAllColumns = true;
                }
            }


            if (!haveAllColumns) {
                RecordHandle rh = page.fetchFromSlot(
                        (RecordHandle) null,
                        scan_position.current_slot,
                        fullKey,
                        fetchDescriptor,
                        true);


                if (SanityManager.DEBUG) {
                    SanityManager.ASSERT(rh != null, "Row not found");
                }
            }


            scan_position.current_positionKey = fullKey;
            // Don't null out current_rh, we might be able to use it later if
            // no rows are moved off the page.
            //scan_position.current_rh = null;
            scan_position.versionWhenSaved = page.getPageVersion();
            scan_position.current_slot = Page.INVALID_SLOT_NUMBER;


        } finally {
            scan_position.current_leaf.release();
            scan_position.current_leaf = null;

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                leaf.page.recordCount() - 1 - leaf.page.nonDeletedRecordCount();


            if (num_possible_commit_delete > 0)
            {


                Page page   = leaf.page;




                // RowLocation column is in last column of template.
                FetchDescriptor lock_fetch_desc = 
                    RowUtil.getFetchDescriptorConstant(
                        scratch_template.length - 1);


                // loop backward so that purges which affect the slot table 
                // don't affect the loop (ie. they only move records we 
                // have already looked at).
                for (int slot_no = page.recordCount() - 1; 
                     slot_no > 0; 
                     slot_no--) 
                {
                    if (page.isDeletedAtSlot(slot_no))
                    {
                        // try to get an exclusive lock on the row, if we can 
                        // then the row is a committed deleted row and it is 
                        // safe to purge it.
                        if (btree_locking_policy.lockScanCommittedDeletedRow(
                                open_btree, leaf, scratch_template, 
                                lock_fetch_desc, slot_no))
                        {
                            // the row is a committed deleted row, purge it.
                            page.purgeAtSlot(slot_no, 1, true);


                            purged_at_least_one_row = true;
                        }
                    }
                }

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            SanityManager.ASSERT(container != null, 
                "ControlRow.Get() is being called on a closed container.");
        }


    // Get the page, waiting if necessary.  The page is returned latched.
    Page page = container.getPage(pageNumber);


        if (SanityManager.DEBUG)
        {
      if (page == null)
              SanityManager.THROWASSERT(

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    long            pageNumber)
    throws StandardException
  {
    // Try to get the page without waiting.  If we would have
    // to wait, return null.
    Page page = open_btree.container.getUserPageNoWait(pageNumber);
    if (page == null)
      return null; 


    // Got the page without waiting.  Return the corresponding
    // control row.

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                // Remember the time stamp on the first page of the column
                // chain.  This is to prevent the case where the post commit
                // work gets fired twice, in that case, the second time it is
                // fired, this overflow page may not part of this row chain
                // that is being updated.
                Page firstPageOnColumnChain = getOverflowPage(overflowPage);
                PageTimeStamp ts = firstPageOnColumnChain.currentTimeStamp();
                firstPageOnColumnChain.unlatch();


                RawTransaction rxact = (RawTransaction)owner.getTransaction();


                ReclaimSpace work = 
                    new ReclaimSpace(ReclaimSpace.COLUMN_CHAIN,

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        // Remember the time stamp on the first page of the column
        // chain.  This is to prevent the case where the post commit
        // work gets fired twice, in that case, the second time it is
        // fired, this overflow page may not part of this row chain
        // that is being updated.
        Page firstPageOnColumnChain = getOverflowPage(overflowPage);
        PageTimeStamp ts = firstPageOnColumnChain.currentTimeStamp();
        firstPageOnColumnChain.unlatch();


        RawTransaction rxact = (RawTransaction)owner.getTransaction();


        ReclaimSpace work = 
          new ReclaimSpace(ReclaimSpace.COLUMN_CHAIN,

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