Class SortBufferRowSource

    • Field Detail

      • sortBuffer

        SortBuffer sortBuffer
        The Sort buffer where rows come from
      • maxFreeListSize

        private int maxFreeListSize
      • writingToDisk

        private boolean writingToDisk
    • Method Detail

      • getNextRowFromRowSource

        public DataValueDescriptor[] getNextRowFromRowSource()
        Description copied from interface: RowSource
        Get the next row as an array of column objects. The column objects can be a JBMS Storable or any Serializable/Externalizable/Formattable/Streaming type.
        A return of null indicates that the complete set of rows has been read.

        A null column can be specified by leaving the object null, or indicated by returning a non-null getValidColumns. On streaming columns, it can be indicated by returning a non-null get FieldStates.

        If RowSource.needToClone() is true then the returned row (the DataValueDescriptor[]) is guaranteed not to be modified by drainer of the RowSource (except that the input stream will be read, of course) and drainer will keep no reference to it before making the subsequent nextRow call. So it is safe to return the same DataValueDescriptor[] in subsequent nextRow calls if that is desirable for performance reasons.

        If RowSource.needToClone() is false then the returned row (the DataValueDescriptor[]) may be be modified by drainer of the RowSource, and the drainer may keep a reference to it after making the subsequent nextRow call. In this case the client should severe all references to the row after returning it from getNextRowFromRowSource().

        Specified by:
        getNextRowFromRowSource in interface RowSource
      • needsToClone

        public boolean needsToClone()
        Description copied from interface: RowSource
        Does the caller of getNextRowFromRowSource() need to clone the row in order to keep a reference to the row past the getNextRowFromRowSource() call which returned the row. This call must always return the same for all rows in a RowSource (ie. the caller will call this once per scan from a RowSource and assume the behavior is true for all rows in the RowSource).
        Specified by:
        needsToClone in interface RowSource
        See Also:
        RowSource.needsToClone()
      • rowLocation

        public void rowLocation​(RowLocation rl)
        Description copied from interface: RowLocationRetRowSource
        rowLocation is a callback for the drainer of the row source to return the rowLocation of the current row, i.e, the row that is being returned by getNextRowFromRowSource. This interface is for the purpose of loading a base table with index. In that case, the indices can be built at the same time the base table is laid down once the row location of the base row is known. This is an example pseudo code on how this call is expected to be used:
                        boolean needsRL = rowSource.needsRowLocation();
                        DataValueDescriptor[] row;
                        while((row = rowSource.getNextRowFromRowSource()) != null)
                        {
                                RowLocation rl = heapConglomerate.insertRow(row);
                                if (needsRL)
                                        rowSource.rowLocation(rl);
                        }
                        

        NeedsRowLocation and rowLocation will ONLY be called by a drainer of the row source which CAN return a row location. Drainer of row source which cannot return rowLocation will guarantee to not call either callbacks. Conversely, if NeedsRowLocation is called and it returns true, then for every row return by getNextRowFromRowSource, a rowLocation callback must also be issued with the row location of the row. Implementor of both the source and the drain of the row source must be aware of this protocol.
        The RowLocation object is own by the caller of rowLocation, in other words, the drainer of the RowSource. This is so that we don't need to new a row location for every row. If the Row Source wants to keep the row location, it needs to clone it (RowLocation is a ClonableObject).
        Specified by:
        rowLocation in interface RowLocationRetRowSource
      • closeForEndTransaction

        public boolean closeForEndTransaction​(boolean closeHeldScan)
        Close the scan
        Specified by:
        closeForEndTransaction in interface ScanManager
        Parameters:
        closeHeldScan - If true, means to close scan even if it has been opened to be kept opened across commit. This is used to close these scans on abort.
        Returns:
        boolean indicating that the close has resulted in a real close of the scan. A held scan will return false if called by closeForEndTransaction(false), otherwise it will return true. A non-held scan will always return true.
      • closeRowSource

        public void closeRowSource()
        Close the rowSource
        Specified by:
        closeRowSource in interface RowSource
      • next

        public boolean next()
                     throws StandardException
        Description copied from interface: ScanController
        Move to the next position in the scan. If this is the first call to next(), the position is set to the first row. Returns false if there is not a next row to move to. It is possible, but not guaranteed, that this method could return true again, after returning false, if some other operation in the same transaction appended a row to the underlying conglomerate.
        Specified by:
        next in interface GroupFetchScanController
        Specified by:
        next in interface ScanController
        Returns:
        True if there is a next position in the scan, false if there isn't.
        Throws:
        StandardException - Standard exception policy.
      • fetchNext

        public final boolean fetchNext​(DataValueDescriptor[] row)
                                throws StandardException
        Description copied from interface: ScanController
        Fetch the (partial) row at the next position of the Scan. If there is a valid next position in the scan then the value in the destRow storable row is replaced with the value of the row at the current scan position. The columns of the destRow row must be of the same type as the actual columns in the underlying conglomerate. The resulting contents of destRow after a fetchNext() which returns false is undefined. The result of calling fetchNext(row) is exactly logically equivalent to making a next() call followed by a fetch(row) call. This interface allows implementations to optimize the 2 calls if possible.
        Specified by:
        fetchNext in interface ScanController
        Parameters:
        row - The destRow row into which the value of the next position in the scan is to be stored.
        Returns:
        True if there is a next position in the scan, false if there isn't.
        Throws:
        StandardException - Standard exception policy.
        See Also:
        ScanController.fetch(org.apache.derby.iapi.types.DataValueDescriptor[]), RowUtil