Interface RowOrdering
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- All Known Implementing Classes:
RowOrderingImpl
public interface RowOrdering
This interface provides a representation of the ordering of rows in a ResultSet.
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Field Summary
Fields Modifier and Type Field Description static int
ASCENDING
static int
DESCENDING
static int
DONTCARE
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Method Summary
All Methods Instance Methods Abstract Methods Modifier and Type Method Description 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.boolean
isColumnAlwaysOrdered(int tableNumber, int columnNumber)
Return true if the column is always ordered.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 positionvoid
removeOptimizable(int tableNumber)
Tell this row ordering that it is no longer ordered on the given table.
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Field Detail
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ASCENDING
static final int ASCENDING
- See Also:
- Constant Field Values
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DESCENDING
static final int DESCENDING
- See Also:
- Constant Field Values
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DONTCARE
static final int DONTCARE
- See Also:
- Constant Field Values
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Method Detail
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orderedOnColumn
boolean orderedOnColumn(int direction, int orderPosition, int tableNumber, int columnNumber) throws StandardException
Tell whether this ordering is ordered on the given column in the given position- 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 questioncolumnNumber
- 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
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orderedOnColumn
boolean orderedOnColumn(int direction, int tableNumber, int columnNumber) throws 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.- 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 questioncolumnNumber
- 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
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addOrderedColumn
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).- 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)
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nextOrderPosition
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).- Parameters:
direction
- One of ASCENDING, DESCENDING, or DONTCARE. DONTCARE can be used for things like columns with constant value, and for one-row tables.
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optimizableAlwaysOrdered
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.- Parameters:
optimizable
- The table in question
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columnAlwaysOrdered
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 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.- Parameters:
optimizable
- The table in questioncolumnNumber
- The number of the column in question.
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isColumnAlwaysOrdered
boolean isColumnAlwaysOrdered(int tableNumber, int columnNumber)
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.- Parameters:
tableNumber
- The table in questioncolumnNumber
- The number of the column in question.- Returns:
- true means this column is always ordered
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alwaysOrdered
boolean alwaysOrdered(int tableNumber)
Ask whether the given table is always ordered.
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removeOptimizable
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.- Parameters:
tableNumber
- The number of the table to remove from this RowOrdering.
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addUnorderedOptimizable
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.
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copy
void copy(RowOrdering copyTo)
Copy the contents of this RowOrdering to the given RowOrdering.
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