Class RowOrderingImpl

java.lang.Object
org.apache.derby.impl.sql.compile.RowOrderingImpl
All Implemented Interfaces:
RowOrdering

class RowOrderingImpl extends Object implements RowOrdering
  • Field Details

    • ordering

      private final ArrayList<ColumnOrdering> ordering
      List of ColumnOrderings.
    • columnsAlwaysOrdered

      ColumnOrdering columnsAlwaysOrdered
    • alwaysOrderedOptimizables

      private final ArrayList<Optimizable> alwaysOrderedOptimizables
      List of table numbers for tables that are always ordered. This happens for one-row tables.
    • currentColumnOrdering

      ColumnOrdering currentColumnOrdering
    • unorderedOptimizables

      private final ArrayList<Optimizable> unorderedOptimizables
      List of unordered Optimizables.
  • Constructor Details

    • RowOrderingImpl

      RowOrderingImpl()
  • Method Details

    • isColumnAlwaysOrdered

      public boolean isColumnAlwaysOrdered(int tableNumber, int columnNumber)
      Description copied from interface: RowOrdering
      Return true if the column is always ordered. That will be true if the column has a constant comparison predicate on it or it is involved in a equijoin with an optimizable which is always ordered on the column on which the equijoin is happening.
      Specified by:
      isColumnAlwaysOrdered in interface RowOrdering
      Parameters:
      tableNumber - The table in question
      columnNumber - The number of the column in question.
      Returns:
      true means this column is always ordered
      See Also:
    • orderedOnColumn

      public boolean orderedOnColumn(int direction, int orderPosition, int tableNumber, int columnNumber) throws StandardException
      Description copied from interface: RowOrdering
      Tell whether this ordering is ordered on the given column in the given position
      Specified by:
      orderedOnColumn in interface RowOrdering
      Parameters:
      direction - One of ASCENDING, DESCENDING, or DONTCARE depending on the requirements of the caller. An ORDER BY clause cares about direction, while DISTINCT and GROUP BY do not.
      orderPosition - The position in the ordering list. For example, for ORDER BY A, B, position 0 has column A, and position 1 has column B. Note that for an ordering, more than one column can be in a single ordering position: for example, in the query SELECT * FROM S, T WHERE S.A = T.B ORDER BY T.B columns S.A and T.B will be in the same ordering positions because they are equal. Also, constant values are considered ordered in all positions (consider SELECT A FROM T WHERE A = 1 ORDER BY A).
      tableNumber - The table number of the Optimizable containing the column in question
      columnNumber - The column number in the table (one-based).
      Returns:
      true means this ordering is ordered on the given column in the given position.
      Throws:
      StandardException - Thrown on error
      See Also:
    • orderedOnColumn

      public boolean orderedOnColumn(int direction, int tableNumber, int columnNumber) throws StandardException
      Description copied from interface: RowOrdering
      Tell whether this ordering is ordered on the given column. This is similar to the method above, but it checks whether the column is ordered in any position, rather than a specified position. This is useful for operations like DISTINCT and GROUP BY.
      Specified by:
      orderedOnColumn in interface RowOrdering
      Parameters:
      direction - One of ASCENDING, DESCENDING, or DONTCARE depending on the requirements of the caller. An ORDER BY clause cares about direction, while DISTINCT and GROUP BY do not.
      tableNumber - The table number of the Optimizable containing the column in question
      columnNumber - The column number in the table (one-based).
      Returns:
      true means this ordering is ordered on the given column in the given position.
      Throws:
      StandardException - Thrown on error
      See Also:
    • addOrderedColumn

      public void addOrderedColumn(int direction, int tableNumber, int columnNumber)
      Description copied from interface: RowOrdering
      Add a column to this RowOrdering in the current order position. This is a no-op if there are any unordered optimizables in the join order (see below).
      Specified by:
      addOrderedColumn in interface RowOrdering
      Parameters:
      direction - One of ASCENDING, DESCENDING, or DONTCARE. DONTCARE can be used for things like columns with constant value, and for one-row tables.
      tableNumber - The table the column is in.
      columnNumber - The column number in the table (one-based)
      See Also:
    • nextOrderPosition

      public void nextOrderPosition(int direction)
      Description copied from interface: RowOrdering
      Move to the next order position for adding ordered columns. This is a no-op if there are any unordered optimizables in the join order (see below).
      Specified by:
      nextOrderPosition in interface RowOrdering
      Parameters:
      direction - One of ASCENDING, DESCENDING, or DONTCARE. DONTCARE can be used for things like columns with constant value, and for one-row tables.
      See Also:
    • optimizableAlwaysOrdered

      public void optimizableAlwaysOrdered(Optimizable optimizable)
      Description copied from interface: RowOrdering
      Tell this RowOrdering that it is always ordered on the given optimizable This is useful when considering a unique index where there is an equality match on the entire key - in this case, all the columns are ordered, regardless of the direction or position, or even whether the columns are in the index.
      Specified by:
      optimizableAlwaysOrdered in interface RowOrdering
      Parameters:
      optimizable - The table in question
    • columnAlwaysOrdered

      public void columnAlwaysOrdered(Optimizable optimizable, int columnNumber)
      Description copied from interface: RowOrdering
      Tell this RowOrdering that it is always ordered on the given column of the given optimizable. This is useful when a column in the optimizable has an equals comparison with a constant expression or it is involved in a equijoin with an optimizable which is always ordered on the column on which the equijoin is happening. This is reset when the optimizable is removed from this RowOrdering.
      Specified by:
      columnAlwaysOrdered in interface RowOrdering
      Parameters:
      optimizable - The table in question
      columnNumber - The number of the column in question.
      See Also:
    • alwaysOrdered

      public boolean alwaysOrdered(int tableNumber)
      Description copied from interface: RowOrdering
      Ask whether the given table is always ordered.
      Specified by:
      alwaysOrdered in interface RowOrdering
      See Also:
    • removeOptimizable

      public void removeOptimizable(int tableNumber)
      Description copied from interface: RowOrdering
      Tell this row ordering that it is no longer ordered on the given table. Also, adjust the current order position, if necessary. This only works to remove ordered columns from the end of the ordering.
      Specified by:
      removeOptimizable in interface RowOrdering
      Parameters:
      tableNumber - The number of the table to remove from this RowOrdering.
      See Also:
    • removeOptimizable

      private void removeOptimizable(int tableNumber, ArrayList<Optimizable> list)
      Remove all optimizables with the given table number from the given list of optimizables.
    • addUnorderedOptimizable

      public void addUnorderedOptimizable(Optimizable optimizable)
      Description copied from interface: RowOrdering
      Add an unordered optimizable to this RowOrdering. This is to solve the following problem: Suppose we have the query: select * from r, s, t order by r.a, t.b Also suppose there are indexes on r.a and t.b. When the optimizer considers the join order (r, s, t) using the index on r.a, the heap on s, and the index on t.b, the rows from the join order will *NOT* be ordered on t.b, because there is an unordered result set between r and t. So, when s is added to the partial join order, and we then add table t to the join order, we want to ensure that we don't add column t.b to the RowOrdering.
      Specified by:
      addUnorderedOptimizable in interface RowOrdering
      See Also:
    • copy

      public void copy(RowOrdering copyTo)
      Description copied from interface: RowOrdering
      Copy the contents of this RowOrdering to the given RowOrdering.
      Specified by:
      copy in interface RowOrdering
      See Also:
    • rememberCurrentColumnOrdering

      private void rememberCurrentColumnOrdering(int posn)
    • toString

      public String toString()
      Overrides:
      toString in class Object
    • unorderedOptimizablesOtherThan

      private boolean unorderedOptimizablesOtherThan(Optimizable optimizable)
      Returns true if there are unordered optimizables in the join order other than the given one.