Interface ScanController

    • Method Detail

      • delete

        boolean delete()
                throws StandardException
        Delete the row at the current position of the scan.
        Returns:
        true if the delete was successful, false if the current position is no longer valid (ie. if it was already deleted).
        Throws:
        StandardException - Standard exception policy.
      • didNotQualify

        void didNotQualify()
                    throws StandardException
        A call to allow client to indicate that current row does not qualify.

        Indicates to the ScanController that the current row does not qualify for the scan. If the isolation level of the scan allows, this may result in the scan releasing the lock on this row.

        Note that some scan implimentations may not support releasing locks on non-qualifying rows, or may delay releasing the lock until sometime later in the scan (ie. it may be necessary to keep the lock until either the scan is repositioned on the next row or page).

        This call should only be made while the scan is positioned on a current valid row.

        Throws:
        StandardException - Standard exception policy.
      • doesCurrentPositionQualify

        boolean doesCurrentPositionQualify()
                                    throws StandardException
        Returns true if the current position of the scan still qualifies under the set of qualifiers passed to the openScan(). When called this routine will reapply all qualifiers against the row currently positioned and return true if the row still qualifies. If the row has been deleted or no longer passes the qualifiers then this routine will return false. This case can come about if the current scan or another scan on the same table in the same transaction deleted the row or changed columns referenced by the qualifier after the next() call which positioned the scan at this row. Note that for comglomerates which don't support update, like btree's, there is no need to recheck the qualifiers. The results of a fetch() performed on a scan positioned on a deleted row are undefined, note that this can happen even if next() has returned true (for instance the client can delete the row, or if using read uncommitted another thread can delete the row after the next() call but before the fetch).
        Throws:
        StandardException - Standard exception policy.
      • fetch

        void fetch​(DataValueDescriptor[] destRow)
            throws StandardException
        Fetch the (partial) row at the current position of the Scan. 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 number of elements in fetch must be compatible with the number of scan columns requested at the openScan call time.
        A fetch can return a sub-set of the scan columns requested at scan open time by supplying a destRow will less elements than the number of requested columns. In this case the N leftmost of the requested columns are fetched, where N = destRow.length. In the case where all columns are rested and N = 2 then columns 0 and 1 are returned. In the case where the openScan FormatableBitSet requested columns 1, 4 and 7, then columns 1 and 4 would be fetched when N = 2.
        The results of a fetch() performed on a scan after next() has returned false are undefined. A fetch() performed on a scan positioned on a deleted row will throw a StandardException with state = SQLState.AM_RECORD_NOT_FOUND. Note that this can happen even if next() has returned true (for instance the client can delete the row, or if using read uncommitted another thread can delete the row after the next() call but before the fetch).
        Parameters:
        destRow - The row into which the value of the current position in the scan is to be stored.
        Throws:
        StandardException - Standard exception policy.
        See Also:
        RowUtil
      • fetchWithoutQualify

        void fetchWithoutQualify​(DataValueDescriptor[] destRow)
                          throws StandardException
        The same as fetch, except that the qualifiers passed to the openScan() will not be applied. destRow will contain the current row even if it has been changed and no longer qualifies.
        Parameters:
        destRow - The row into which the value of the current position in the scan is to be stored.
        Throws:
        StandardException - Standard exception policy.
      • fetchNext

        boolean fetchNext​(DataValueDescriptor[] destRow)
                   throws StandardException
        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.
        Parameters:
        destRow - 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:
        fetch(org.apache.derby.iapi.types.DataValueDescriptor[]), RowUtil
      • fetchLocation

        void fetchLocation​(RowLocation destRowLocation)
                    throws StandardException
        Fetch the location of the current position in the scan. The destination location is replaced with the location corresponding to the current position in the scan. The destination location must be of the correct actual type to accept a location from the underlying conglomerate location. The results of a fetchLocation() performed on a scan after next() has returned false are undefined. The results of a fetchLocation() performed on a scan positioned on a deleted row are undefined, note that this can happen even if next() has returned true (for instance the client can delete the row, or if using read uncommitted another thread can delete the row after the next() call but before the fetchLocation).
        Throws:
        StandardException - Standard exception policy.
      • isCurrentPositionDeleted

        boolean isCurrentPositionDeleted()
                                  throws StandardException
        Returns true if the current position of the scan is at a deleted row. This case can come about if the current scan or another scan on the same table in the same transaction deleted the row after the next() call which positioned the scan at this row. The results of a fetch() performed on a scan positioned on a deleted row are undefined.
        Throws:
        StandardException - Standard exception policy.
      • next

        boolean next()
              throws StandardException
        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.
        Returns:
        True if there is a next position in the scan, false if there isn't.
        Throws:
        StandardException - Standard exception policy.
      • positionAtRowLocation

        boolean positionAtRowLocation​(RowLocation rl)
                               throws StandardException
        Positions the scan at row location and locks the row. If the scan is not opened, it will be reopened if this is a holdable scan and there has not been any operations which causes RowLocations to be invalidated.
        Parameters:
        rl - RowLocation for the new position for the scan. The RowLocation submitted should be a RowLocation which has previously been returned by this ScanController.
        Returns:
        true if the scan has been positioned at the RowLocation. false if the scan could not be positioned.
        Throws:
        StandardException - Standard exception policy.