|
| |
|
| org.apache.derby.vti.VTICosting
All known Subclasses: org.apache.derby.diag.SpaceTable, org.apache.derby.diag.TransactionTable, org.apache.derby.diag.ErrorMessages, org.apache.derby.diag.LockTable,
| VTICosting | | public interface VTICosting (Code) | | VTICosting is the interface that the query optimizer uses
to cost VTIs.
The methods on the interface provide the optimizer
with the following information:
- the estimated number of rows returned by the VTI in a single instantiation.
- the estimated cost to instantiate and iterate through the VTI.
- whether or not the VTI can be instantiated multiple times within a single query execution
This class can only be used within an SQL-J statement. Using the methods
in application-side Java code results in Exceptions being thrown.
See Also: org.apache.derby.vti.VTIEnvironment |
| Field Summary | |
| final public static double | defaultEstimatedCost
A useful constant: The default estimated cost of instantiating and iterating throught a VTI. | | final public static double | defaultEstimatedRowCount
A useful constant: the default estimated number of rows returned by a VTI. |
| defaultEstimatedCost | | final public static double defaultEstimatedCost(Code) | | A useful constant: The default estimated cost of instantiating and iterating throught a VTI.
|
| defaultEstimatedRowCount | | final public static double defaultEstimatedRowCount(Code) | | A useful constant: the default estimated number of rows returned by a VTI.
|
| getEstimatedCostPerInstantiation | | public double getEstimatedCostPerInstantiation(VTIEnvironment vtiEnvironment) throws SQLException(Code) | | Get the estimated cost for a single instantiation of a VTI.
Parameters:
vtiEnvironment - The VTIEnvironment. The estimated cost for a single instantiation of a VTI.
exception:
SQLException - thrown if the costing fails. |
| getEstimatedRowCount | | public double getEstimatedRowCount(VTIEnvironment vtiEnvironment) throws SQLException(Code) | | Get the estimated row count for a single scan of a VTI.
Parameters:
vtiEnvironment - The VTIEnvironment. The estimated row count for a single scan of a VTI.
exception:
SQLException - thrown if the costing fails. |
| supportsMultipleInstantiations | | public boolean supportsMultipleInstantiations(VTIEnvironment vtiEnvironment) throws SQLException(Code) | | Find out if the ResultSet of the VTI can be instantiated multiple times.
Parameters:
vtiEnvironment - The VTIEnvironment. True if the ResultSet can be instantiated multiple times, false ifcan only be instantiated once.
exception:
SQLException - thrown if the costing fails. |
|
|
|