Interface RequiredRowOrdering

  • All Known Implementing Classes:
    OrderByList

    public interface RequiredRowOrdering
    This interface provides a representation of the required ordering of rows from a ResultSet. Different operations can require ordering: ORDER BY, DISTINCT, GROUP BY. Some operations, like ORDER BY, require that the columns be ordered a particular way, while others, like DISTINCT and GROUP BY, reuire only that there be no duplicates in the result.
    • Method Summary

      All Methods Instance Methods Abstract Methods 
      Modifier and Type Method Description
      void estimateCost​(double estimatedInputRows, RowOrdering rowOrdering, CostEstimate resultCost)
      Estimate the cost of doing a sort for this row ordering, given the number of rows to be sorted.
      boolean getSortNeeded()  
      void sortNeeded()
      Indicate that a sort is necessary to fulfill this required ordering.
      void sortNotNeeded()
      Indicate that a sort is *NOT* necessary to fulfill this required ordering.
      int sortRequired​(RowOrdering rowOrdering, OptimizableList optimizableList, int[] proposedJoinOrder)
      Tell whether sorting is required for this RequiredRowOrdering, given a RowOrdering.
      int sortRequired​(RowOrdering rowOrdering, JBitSet tableMap, OptimizableList optimizableList, int[] proposedJoinOrder)
      Tell whether sorting is required for this RequiredRowOrdering, given a RowOrdering representing a partial join order, and a bit map telling what tables are represented in the join order.
    • Method Detail

      • sortRequired

        int sortRequired​(RowOrdering rowOrdering,
                         OptimizableList optimizableList,
                         int[] proposedJoinOrder)
                  throws StandardException
        Tell whether sorting is required for this RequiredRowOrdering, given a RowOrdering.
        Parameters:
        rowOrdering - The order of rows in question
        optimizableList - The list of join participants
        proposedJoinOrder - The current join order being considered by the optimizer. We need to look into this to determine if the outer optimizables are single row result set if the order by column is on an inner optimizable and that inner optimizable is not a one. proposedJoinOrder is a map onto optimizableList: it contains indexes of optimizables in that list in the join order proposed, cf. OptimizerImpl#proposedJoinOrder.
        Returns:
        SORT_REQUIRED if sorting is required, ELIMINATE_DUPS if no sorting is required but duplicates must be eliminated (i.e. the rows are in the right order but there may be duplicates), NOTHING_REQUIRED is no operation is required
        Throws:
        StandardException - Thrown on error
      • sortRequired

        int sortRequired​(RowOrdering rowOrdering,
                         JBitSet tableMap,
                         OptimizableList optimizableList,
                         int[] proposedJoinOrder)
                  throws StandardException
        Tell whether sorting is required for this RequiredRowOrdering, given a RowOrdering representing a partial join order, and a bit map telling what tables are represented in the join order. This is useful for reducing the number of cases the optimizer has to consider.
        Parameters:
        rowOrdering - The order of rows in the partial join order
        tableMap - A bit map of the tables in the partial join order
        optimizableList - The list of join participants
        proposedJoinOrder - The current join order being considered by the optimizer. We need to look into this to determine if the outer optimizables are single row result set if the order by column is on an inner optimizable and that inner optimizable is not a one. proposedJoinOrder is a map onto optimizableList: it contains indexes of optimizables in that list in the join order proposed, cf. OptimizerImpl#proposedJoinOrder. DERBY-3926 and DERBY-6148
        Returns:
        SORT_REQUIRED if sorting is required, ELIMINATE_DUPS if no sorting is required by duplicates must be eliminated (i.e. the rows are in the right order but there may be duplicates), NOTHING_REQUIRED is no operation is required
        Throws:
        StandardException - Thrown on error
      • estimateCost

        void estimateCost​(double estimatedInputRows,
                          RowOrdering rowOrdering,
                          CostEstimate resultCost)
                   throws StandardException
        Estimate the cost of doing a sort for this row ordering, given the number of rows to be sorted. This does not take into account whether the sort is really needed. It also estimates the number of result rows.
        Parameters:
        estimatedInputRows - The estimated number of rows to sort
        rowOrdering - The ordering of the input rows
        resultCost - A place to store the resulting cost
        Throws:
        StandardException - Thrown on error
      • sortNeeded

        void sortNeeded()
        Indicate that a sort is necessary to fulfill this required ordering. This method may be called many times during a single optimization.
      • sortNotNeeded

        void sortNotNeeded()
        Indicate that a sort is *NOT* necessary to fulfill this required ordering. This method may be called many times during a single optimization.
      • getSortNeeded

        boolean getSortNeeded()