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

                // Need to get an exclusive scan lock on the page before we can
                // do any sort of purges, otherwise other concurrent scans would
                // not work.  If we can't get the lock NOWAIT, just give up on
                // purging rows and do the split without reclaiming rows.


                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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        // need to open the container and insert the row.  Since we are
        // creating it no need to bother with locking since no one can get
        // to it until after we have created it and returned it's id.
        ContainerHandle container = null;
        Page            page      = null;


        try
        {
            container = 
                rawtran.openContainer(
                    id, (LockingPolicy) null, 
                    ContainerHandle.MODE_FORUPDATE | 
                        (isTemporary() ? ContainerHandle.MODE_TEMP_IS_KEPT : 0));


            // row in slot 0 of heap page 1 which is just a single column with
            // the heap entry.
            DataValueDescriptor[] control_row = new DataValueDescriptor[1];
            control_row[0] = this;


            page =
                container.getPage(ContainerHandle.FIRST_PAGE_NUMBER);


            page.insertAtSlot(
                Page.FIRST_SLOT_NUMBER,
                control_row,
                (FormatableBitSet) null,
                (LogicalUndo) null, 
                Page.INSERT_OVERFLOW,
                AccessFactoryGlobals.HEAP_OVERFLOW_THRESHOLD);
            page.unlatch();
            page = null;


            // Don't include the control row in the estimated row count.
            container.setEstimatedRowCount(0, /* unused flag */ 0);
        }
        finally
        {
            if (container != null)
                container.close();
            if (page !=null)
                page.unlatch();
        }
  }

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        throws StandardException
    {
        // need to open the container and update the row containing the 
        // serialized format of the heap.  
        ContainerHandle container = null;
        Page            page      = null;
        Transaction     rawtran   = xact_manager.getRawStoreXact();


        try
        {
            container = 
                rawtran.openContainer(
                    id, 
                    rawtran.newLockingPolicy(
                        LockingPolicy.MODE_CONTAINER,
                        TransactionController.ISOLATION_SERIALIZABLE, true),
                    ContainerHandle.MODE_FORUPDATE | 
                        (isTemporary() ? ContainerHandle.MODE_TEMP_IS_KEPT : 0));


            if (column_id != format_ids.length)
            {
                if (SanityManager.DEBUG)
                    SanityManager.THROWASSERT(
                        "column_id = " + column_id +
                        "format_ids.length = " + format_ids.length +
                        "format_ids = " + format_ids);


                throw(StandardException.newException(
                        SQLState.HEAP_TEMPLATE_MISMATCH,
                        new Long(column_id), 
                        new Long(this.format_ids.length)));
            }


            // create a new array, and copy old values to it.
            int[] old_format_ids = format_ids;
            format_ids              = new int[old_format_ids.length + 1];
            System.arraycopy(
                old_format_ids, 0, format_ids, 0, old_format_ids.length);


            // add the new column
            format_ids[old_format_ids.length] = 
                template_column.getTypeFormatId();


           
            // row in slot 0 of heap page 1 which is just a single column with
            // the heap entry.
            DataValueDescriptor[] control_row = new DataValueDescriptor[1];
            control_row[0] = this;


            page =
                container.getPage(ContainerHandle.FIRST_PAGE_NUMBER);


            page.updateAtSlot(
                Page.FIRST_SLOT_NUMBER,
                control_row,
                (FormatableBitSet) null);


            page.unlatch();
            page = null;
        }
        finally
        {
            if (container != null)
                container.close();
            if (page !=null)
                page.unlatch();
        }


        return;
    }

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            heapcontroller = new HeapController();


            heapcontroller.init(open_conglom);


            Page page   = open_conglom.getContainer().getFirstPage();


            boolean purgingDone = false;


            while (page != null)
            {
                long pageno = page.getPageNumber();
                purgingDone = heapcontroller.purgeCommittedDeletes(page);


                if (purgingDone)
                {
                    page = null;


                    // commit xact to free resouurces ASAP, commit will
                    // unlatch the page if it has not already been unlatched
                    // by a remove.
                    open_conglom.getXactMgr().commitNoSync(
                                TransactionController.RELEASE_LOCKS);


                    // the commit closes the underlying container, so let
                    // the heapcontroller know this has happened.  Usually
                    // the transaction takes care of this, but this controller
                    // is internal, so the transaction does not know about it.
                    heapcontroller.closeForEndTransaction(false);
                    
                    // the commit will close the underlying 
                    open_conglom.reopen();
                }
                else
                {
                    page.unlatch();
                    page = null;
                }


                page = open_conglom.getContainer().getNextPage(pageno);
            }

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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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                    {
                        scan_position.current_positionKey = 
                            runtime_mem.get_row_for_export(getRawTran());




                        Page page = scan_position.current_leaf.getPage();




                        RecordHandle rh =
                            page.fetchFromSlot(
                                (RecordHandle) null,
                                page.getSlotNumber(scan_position.current_rh), 
                                scan_position.current_positionKey, 
                                (FetchDescriptor) null,
                                true);


                        if (SanityManager.DEBUG)

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            // the post commit work will just skip it.
            control_row = ControlRow.getNoWait(open_btree, pageno);


            if (control_row != null)
            {
                Page page   = control_row.page;


                // The number records that can be reclaimed is:
                // total recs - control row - recs_not_deleted
                int num_possible_commit_delete = 
                    page.recordCount() - 1 - page.nonDeletedRecordCount();


                if (num_possible_commit_delete > 0)
                {
                    // 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))
                        {


                            if (page.recordCount() == 2)
                            {
                                // About to purge last row from page so 
                                // remember the key so we can shrink the 
                                // tree.
                                shrink_key = this.getShrinkKey(
                                    open_btree, control_row, slot_no);
                            }


                            page.purgeAtSlot(slot_no, 1, true);


                            if (SanityManager.DEBUG)
                            {
                                if (SanityManager.DEBUG_ON(
                                        "verbose_btree_post_commit"))
                                {
                                    System.out.println(
                                        "Purging row[" + slot_no + "]" + 
                                        "on page:" + pageno + ".\n");
                                }
                            }
                        }
                    }
                }


                if (page.recordCount() == 1)
                {
                    if (SanityManager.DEBUG)
                    {
                        if (SanityManager.DEBUG_ON("verbose_btree_post_commit"))
                        {

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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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        // 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,

View Full Code Here

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