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org.apache.derby.iapi.sql.compile
Interface RowOrdering
- public interface RowOrdering
This interface provides a representation of the ordering of rows in a ResultSet.
| Field Summary | |
static int |
ASCENDING
|
static int |
DESCENDING
|
static int |
DONTCARE
|
| Method Summary | |
void |
addOrderedColumn(int direction,
int tableNumber,
int columnNumber)
Add a column to this RowOrdering in the current order position. |
void |
addUnorderedOptimizable(Optimizable optimizable)
Add an unordered optimizable to this RowOrdering. |
boolean |
alwaysOrdered(int tableNumber)
Ask whether the given table is always ordered. |
void |
columnAlwaysOrdered(Optimizable optimizable,
int columnNumber)
Tell this RowOrdering that it is always ordered on the given column of the given optimizable. |
void |
copy(RowOrdering copyTo)
Copy the contents of this RowOrdering to the given RowOrdering. |
void |
nextOrderPosition(int direction)
Move to the next order position for adding ordered columns. |
void |
optimizableAlwaysOrdered(Optimizable optimizable)
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. |
boolean |
orderedOnColumn(int direction,
int tableNumber,
int columnNumber)
Tell whether this ordering is ordered on the given column. |
boolean |
orderedOnColumn(int direction,
int orderPosition,
int tableNumber,
int columnNumber)
Tell whether this ordering is ordered on the given column in the given position |
void |
removeOptimizable(int tableNumber)
Tell this row ordering that it is no longer ordered on the given table. |
| Field Detail |
ASCENDING
public static final int ASCENDING
- See Also:
- Constant Field Values
DESCENDING
public static final int DESCENDING
- See Also:
- Constant Field Values
DONTCARE
public static final int DONTCARE
- See Also:
- Constant Field Values
| Method Detail |
orderedOnColumn
public boolean orderedOnColumn(int direction,
int orderPosition,
int tableNumber,
int columnNumber)
throws org.apache.derby.iapi.error.StandardException
- Tell whether this ordering is ordered on the given column in
the given position
orderedOnColumn
public boolean orderedOnColumn(int direction,
int tableNumber,
int columnNumber)
throws org.apache.derby.iapi.error.StandardException
- 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.
addOrderedColumn
public void addOrderedColumn(int direction,
int tableNumber,
int columnNumber)
- 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).
nextOrderPosition
public void nextOrderPosition(int direction)
- 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).
optimizableAlwaysOrdered
public void optimizableAlwaysOrdered(Optimizable optimizable)
- 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.
columnAlwaysOrdered
public void columnAlwaysOrdered(Optimizable optimizable, int columnNumber)
- 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.
This is reset when the optimizable is removed from this RowOrdering.
alwaysOrdered
public boolean alwaysOrdered(int tableNumber)
- Ask whether the given table is always ordered.
removeOptimizable
public void removeOptimizable(int tableNumber)
- 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.
addUnorderedOptimizable
public void addUnorderedOptimizable(Optimizable optimizable)
- 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.
copy
public void copy(RowOrdering copyTo)
- Copy the contents of this RowOrdering to the given RowOrdering.
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SUMMARY: JAVADOC | SOURCE | DOWNLOAD | NESTED | FIELD | CONSTR | METHOD |
DETAIL: FIELD | CONSTR | METHOD | ||||||||