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.
  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    static final int
     
    static final int
     
    static final int
     
  • Method Summary

    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
     
    void
    Indicate that a sort is necessary to fulfill this required ordering.
    void
    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.
  • Field Details

  • Method Details

    • 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()