Interface ContainerHandle

  • All Known Subinterfaces:
    RawContainerHandle
    All Known Implementing Classes:
    BaseContainerHandle

    public interface ContainerHandle
    A Container contains a contigious address space of pages, the pages start at page number Container.FIRST_PAGE_NUMBER and are numbered sequentially. The page size is set at addContainer() time. RESOLVE: this style of coding is not currently enforced If the caller calls getPage (or one of its variants) more than once on the same page, the caller must call unlatch a corresponding number of times in order to ensure that the page is latched. For example:

        Container c;
            Page p1 = c.getPage(Container.FIRST_PAGE_NUMBER);
            Page p2 = c.getPage(Container.FIRST_PAGE_NUMBER);
            p1.unlatch();  -- Page is still latched.
            p2.unlatch();  -- Page is now unlatched.
            

    There is no restriction on the order in which latching and unlatching is done. In the example, p1 could have been unlatched after p2 with no ill effects.

    Open container modes ContainerHandle.MODE are used to open or create the container. Unlike TableProperties, MODEs are not permanantely associated with the container, it is effective only for the lifetime of the containerHandle itself.
    A container may use any of these mode flags when it is opened.

    • MODE_READONLY - Open the container in read only mode.
    • MODE_FORUPDATE - Open the container in update mode, if the underlying storage does not allow updates then the container will be opned in read only mode.
    • MODE_UNLOGGED - If Unset, any changes to the container are logged. If set, any user changes to the container are unlogged. It is guaranteed at commit time that all changes made during the transaction will have been flushed to disk. Using this mode automatically opens the container in container locking, isolation 3 level. The state of the container following an abort or any type of rollback is unspecified.
    • MODE_CREATE_UNLOGGED - If set, not only are user changes to the container are unlogged, page allocations are also unlogged. This MODE is only useful for container is created in the same statement and no change on the container (other than the create) is ever logged. The difference between MODE_UNLOGGED and MODE_CREATE_UNLOGGED is that page allocation is also unlogged and commit of nested transaction will not cause the container to be forced from the cache. Unlike MODE_UNLOGGED, MODE_CREATE_UNLOGGED does not force the cache. It is up to the client of raw store to force the cache at the appropriate time - this allows a statement to create and open the container serveral times for bulk loading without logging or doing any synchronous I/O.
    • MODE_LOCK_NOWAIT - if set, then don't wait for the container lock, else wait for the container lock. This flag only dictates whether the lock should be waited for or not. After the container is successfully opened, whether this bit is set or not has no effect on the container handle.
    If neither or both of the {MODE_READONLY, MODE_FORUPDATE} modes are specified then the behaviour of the container is unspecified.
    MODE_UNLOGGED must be set for MODE_CREATE_UNLOGGED to be set.

    Temporary Containers
    If when creating a container the segment used is ContainerHandle.TEMPORARY_SEGMENT then the container is a temporary container. Temporary containers are not logged or locked and do not live across re-boots of the system. In addition any abort or rollback including rollbacks to savepoints truncate the container if it has been opened for update since the last commit or abort. Temporary containers are private to a transaction and must only be used a single thread within the transaction at any time, these restrictions are not currently enforced.
    When opening a temporary container for update access these additional mode flags may be used

    • MODE_TRUNCATE_ON_COMMIT - At commit/abort time container is truncated.
    • MODE_DROP_ON_COMMIT - At commit/abort time the container is dropped.
    • MODE_TEMP_IS_KEPT - At commit/abort time the container is kept around.
    If a temporary container is opened multiple times in the same transaction with different modes then the most severe mode is used, ie. none < truncate on commit < drop on commit. The MODE_UNLOGGED, MODE_CREAT_UNLOGGED flags are ignored when opening a temporary container, not logged is always assumed.
    • Method Detail

      • getUniqueId

        java.lang.Object getUniqueId()
        Return my unique identifier, this identifier will be unique to each instance of an open container handle. This id is used by the locking system to group locks to an open container handle.
      • isReadOnly

        boolean isReadOnly()
        Is the container opened for read only or update?
        Returns:
        true if container is opened for read only, else false.
      • addPage

        Page addPage()
              throws StandardException
        Add an empty page to the container and obtain exclusive access to it.

        Note that the added page may not be the last page in the Container. Once the Page is no longer required the Page's unlatch() method must be called.

        Returns:
        a reference to the page that was added.
        Throws:
        StandardException - If a page could not be allocated.
        See Also:
        Page.unlatch()
      • compressContainer

        void compressContainer()
                        throws StandardException
        Release free space to the OS.

        As is possible release any free space to the operating system. This will usually mean releasing any free pages located at the end of the file using the java truncate() interface.

        Throws:
        StandardException - Standard Derby error policy
      • getReusableRecordIdSequenceNumber

        long getReusableRecordIdSequenceNumber()
                                        throws StandardException
        Get the reusable recordId sequence number.
        Returns:
        version sequence number
        Throws:
        StandardException - Standard Derby error policy
      • addPage

        Page addPage​(int flag)
              throws StandardException
        Add an empty page to the container and obtain exclusive access to it.

        If flag == ADD_PAGE_DEFAULT, this call is identical to addPage().
        If flag == ADD_PAGE_BULK, then this call signifies to the container that this addPage is part of a large number of additional pages and it is desirable to do whatever possible to facilitate adding many subsequent pages. The actual container implementation will decide whether or not to heed this hint and what to do about it.

        Returns:
        a reference to the page that was added.
        Throws:
        StandardException - Standard Derby error policy
        StandardException - If a page could not be allocated.
        See Also:
        Page.unlatch()
      • preAllocate

        void preAllocate​(int numPage)
        Try to preallocate numPage new pages if possible.
      • removePage

        void removePage​(Page page)
                 throws StandardException
        Remove this page from the container and unlatch the page. Caller should commit or abort this transaction ASAP because failure to do so will slow down page allocation of this container.
        The page to be removed must be latched and gotten (or added) by this ContainerHandle. The page should not be used again after this call as if it has been unlatched. If the call to removePage is successful, this page is invalid should not be gotten again with getPage.
        RemovePage will guarantee to unlatch the page even if a StandardException is thrown.

        Locking Policy
        The page will not be freed until the transaction that removed the page commits. A special RecordHandle.DEALLOC_PROTECTION_HANDLE lock will be gotten for the transaction and which is used to prevent the page from being freed. This lock will be held regardless of the default locking policy of the transaction that called removedPage.

        Throws:
        StandardException - Standard Derby error policy
        See Also:
        LockingPolicy, RecordHandle
      • getPage

        Page getPage​(long pageNumber)
              throws StandardException
        Obtain exclusive access to the page with the given page number. Once the Page is no longer required the Page's unlatch() method must be called.

        The Page object is guaranteed to remain in-memory and exclusive to the caller until its unlatch() method is called.

        Returns:
        the required Page or null if the page does not exist or is not valid (i.e, it has been deallocated or freed or never initialized) Note that an overflow page will be returned since it is a valid page.
        Throws:
        StandardException - Standard Derby error policy
      • getPageNoWait

        Page getPageNoWait​(long pageNumber)
                    throws StandardException
        Identical to getPage but returns null immediately if the desired page is already latched by another Container.
        Returns:
        the required Page or null if the page does not exist or the page is already latched.
        Throws:
        StandardException - Standard Derby error policy
      • getUserPageNoWait

        Page getUserPageNoWait​(long pageNumber)
                        throws StandardException
        Obtain exclusive access to the page with the given page number. Will only return a valid, non-overflow user page - so can be used by routines in post commit to get pages to attempt deleted row space reclamation. If for some reason a request is made for an overflow page a null will be returned. Once the Page is no longer required the Page's unlatch() method must be called.

        The Page object is guaranteed to remain in-memory and exclusive to the caller until its unlatch() method is called.

        Returns:
        the required Page or null if the page does not exist or is not valid (i.e, it has been deallocated, freed, never initialized, or is an allocation page or overflow page)
        Throws:
        StandardException - Standard Derby error policy
      • getUserPageWait

        Page getUserPageWait​(long pageNumber)
                      throws StandardException
        Obtain exclusive access to the page with the given page number. Will only return a valid, non-overflow user page - so can be used by routines in post commit to get pages to attempt deleted row space reclamation. If for some reason a request is made for an overflow page a null will be returned. Once the Page is no longer required the Page's unlatch() method must be called.

        The Page object is guaranteed to remain in-memory and exclusive to the caller until its unlatch() method is called.

        Returns:
        the required Page or null if the page does not exist or is not valid (i.e, it has been deallocated, freed, never initialized, or is an allocation page or overflow page)
        Throws:
        StandardException - Standard Derby error policy
      • getFirstPage

        Page getFirstPage()
                   throws StandardException
        Obtain exclusive access to the current first page of the container. Only a valid, non overflow page will be returned. Pages in the container are ordered in an internally defined ordering.

        Note that once this method returns this page may no longer be the first page of the container. I.e, other threads may allocate pages prior to this page number while this page is latched. It is up to the caller of this routine to synchronize this call with addPage to assure that this is the first page.
        As long as the client provide the necessary lock to ensure that no addPage is called, then this page is guaranteed to be the first page of the container in some internally defined ordering of the pages.

        Returns:
        latched page or null if there is no page in the container
        Throws:
        StandardException - Standard Derby error policy
        See Also:
        getPage(long)
      • getNextPage

        Page getNextPage​(long prevNum)
                  throws StandardException
        Obtain exclusive access to the next valid page of the given page number in the container. Only a valid, non overflow page will be returned. Pages in the container are ordered in an internally defined ordering.

        Note that once this method returns this page may no longer be the next page of the container. I.e, other threads may allocate pages prior to this page number while this page is latched. It is up to the caller of this routine to synchronize this call with addPage to assure that this is the first page.
        As long as the client provide the necessary lock to ensure that no addPage is called, then this page is guaranteed to be the next page of the container in some internally defined ordering of the pages.
        If no pages are added or removed, then an iteration such as:

                        for (Page p = containerHandle.getFirstPage();
                                 p != null;
                                 p = containerHandle.getNextPage(p.getPageNumber()))
                        
                        will guarentee to iterate thru and latched all the valid pages 
                        in the container
        Parameters:
        prevNum - the pagenumber of the page previous to the page that is to be gotten. The page which correspond to prevNum may or may not be latched by the caller, but it must be gotten via a page which was (or currently still is) latched, and the page number must be gotten while the container must not have been closed or dropped or removed in the interim. In other words, if the user manufactures a page number, or remembers the page number from a previous session or a previous openContainer, then the behavior of this routine is undefined.
        Returns:
        latched page or null if there is no next page in the container
        Throws:
        StandardException - Standard Derby error policy
        See Also:
        getPage(long)
      • getPageForInsert

        Page getPageForInsert​(int flag)
                       throws StandardException
        Get a page for insert. If RawStore thinks it knows where a potentially suitable page is for insert, it will return it. If RawStore doesn't know where a suitable page for insert is, or if there are no allocated page, then null is returned. If a page is returned, it will be a valid, non-overflow page. A potentially suitable page is one which has enough space for a minium sized record.
        Parameters:
        flag - a GET_PAGE_* flag.
        Returns:
        a valid, non-overflow page. Or null if RawStore doesn't know where to find a good valid, non-overflow page.
        Throws:
        StandardException - Standard Derby error policy
      • getContainerProperties

        void getContainerProperties​(java.util.Properties prop)
                             throws StandardException
        Request the system properties associated with a container.

        Request the value of properties that are associated with a table. The following properties can be requested: derby.storage.pageSize derby.storage.pageReservedSpace derby.storage.minimumRecordSize

        To get the value of a particular property add it to the property list, and on return the value of the property will be set to it's current value. For example: get_prop(ConglomerateController cc) { Properties prop = new Properties(); prop.put("derby.storage.pageSize", ""); cc.getTableProperties(prop); System.out.println( "table's page size = " + prop.getProperty("derby.storage.pageSize"); }

        Parameters:
        prop - Property list to fill in.
        Throws:
        StandardException - Standard exception policy.
      • close

        void close()
        Close me. After using this method the caller must throw away the reference to the Container object, e.g.
                                ref.close();
                                ref = null;
                        

        The container will be closed automatically at the commit or abort of the transaction if this method is not called explictly.
        Any pages that were obtained using me and have not been released using Page's unlatch method are released, and references to them must be thrown away.
        See Also:
        Page.unlatch()
      • getEstimatedRowCount

        long getEstimatedRowCount​(int flag)
                           throws StandardException
        Get the total estimated number of rows in the container, not including overflow rows. This number is a rough estimate and may be grossly off.
        Parameters:
        flag - different flavors of row count (reserved for future use)
        Throws:
        StandardException - Standard Derby error policy
      • setEstimatedRowCount

        void setEstimatedRowCount​(long count,
                                  int flag)
                           throws StandardException
        Set the total estimated number of rows in the container. Often, after a scan, the client of RawStore has a much better estimate of the number of rows in the container then what RawStore has. Use this better number for future reference.
        It is OK for a ReadOnly ContainerHandle to set the estimated row count.
        Parameters:
        count - the estimated number of rows in the container.
        flag - different flavors of row count (reserved for future use)
        Throws:
        StandardException - Standard Derby error policy
      • getEstimatedPageCount

        long getEstimatedPageCount​(int flag)
                            throws StandardException
        Get the total estimated number of allocated (not freed, not deallocated) user pages in the container, including overflow pages. this number is a rough estimate and may be grossly off.
        Parameters:
        flag - different flavors of page count (reserved for future use)
        Throws:
        StandardException - Standard Derby error policy
      • flushContainer

        void flushContainer()
                     throws StandardException
        Flush all dirty pages of the container to disk. Used mainly for UNLOGGED or CREATE_UNLOGGED operation.
        Throws:
        StandardException - Standard Derby error policy
      • getLockingPolicy

        LockingPolicy getLockingPolicy()
        Return the locking policy for this open container.
      • setLockingPolicy

        void setLockingPolicy​(LockingPolicy newLockingPolicy)
        Set the locking policy for this open container
      • makeRecordHandle

        RecordHandle makeRecordHandle​(long pageNumber,
                                      int recordId)
                               throws StandardException
        Return a record handle that is initialized to the given segment id, container id, page number and record id.
        Parameters:
        pageNumber - the page number of the RecordHandle.
        recordId - the record id of the RecordHandle.
        Throws:
        StandardException - Standard Derby exception policy.
        See Also:
        RecordHandle
      • compactRecord

        void compactRecord​(RecordHandle record)
                    throws StandardException
        This record probably has shrunk considerably. Free its reserved space or compact it.
        Parameters:
        record - The record handle, the record must have been locked execlusively already.
        Throws:
        StandardException - Standard Derby exception policy.
      • isTemporaryContainer

        boolean isTemporaryContainer()
                              throws StandardException
        Return true if this containerHandle refers to a temporary container.
        Throws:
        StandardException - Standard Derby exception policy.
      • backupContainer

        void backupContainer​(java.lang.String backupContainerPath)
                      throws StandardException
        Backup the container to the specified path.
        Throws:
        StandardException - Standard Derby error policy