Class Hierarchy Previous Next Index
Interface COM.cloudscape.vti.VTICosting
- public interface VTICosting
Copyright © 1998-2000, Informix Software, Inc. All rights reserved.
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.
Cloudscape reserves the right to change, rename, or
remove this interface at any time.
- See Also:
- COM.cloudscape.database.VTIEnvironment
defaultEstimatedCost-
defaultEstimatedRowCount- Useful constants:
- defaultEstimatedRowCount - The default estimated number of rows returned by a VTI.
getEstimatedCostPerInstantiation(VTIEnvironment)
- Get the estimated cost for a single instantiation of a VTI.
getEstimatedRowCount(VTIEnvironment)
- Get the estimated row count for a single scan of a VTI.
supportsMultipleInstantiations(VTIEnvironment)
- Find out if the VTI can be instantiated multiple times.
defaultEstimatedRowCount
public static final double defaultEstimatedRowCount
Useful constants:
- defaultEstimatedRowCount - The default estimated number of rows returned by a VTI.
- defaultEstimatedCost - The default estimated cost of instantiating and iterating throught a VTI.
defaultEstimatedCost
public static final double defaultEstimatedCost
getEstimatedRowCount
public double getEstimatedRowCount(VTIEnvironment vtiEnvironment) throws java.sql.SQLException
Get the estimated row count for a single scan of a VTI.
- Parameters:
vtiEnvironment
- The VTIEnvironment.
- Returns:
- The estimated row count for a single scan of a VTI.
- Throws:
- java.sql.SQLException - thrown if the costing fails.
getEstimatedCostPerInstantiation
public double getEstimatedCostPerInstantiation(VTIEnvironment vtiEnvironment) throws java.sql.SQLException
Get the estimated cost for a single instantiation of a VTI.
- Parameters:
vtiEnvironment
- The VTIEnvironment.
- Returns:
- The estimated cost for a single instantiation of a VTI.
- Throws:
- java.sql.SQLException - thrown if the costing fails.
supportsMultipleInstantiations
public boolean supportsMultipleInstantiations(VTIEnvironment vtiEnvironment) throws java.sql.SQLException
Find out if the VTI can be instantiated multiple times.
- Parameters:
vtiEnvironment
- The VTIEnvironment.
- Returns:
- The whether or not the VTI can be instantiated multiple times.
- Throws:
- java.sql.SQLException - thrown if the costing fails.
Class Hierarchy Previous Next Index