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VTICosting is the interface that the query optimizer uses to cost VTIs. The methods on the interface provide the optimizer with the following information:
This class can only be used within an SQL-J statement. Using the methods in application-side Java code results in Exceptions being thrown.
IBM Corp reserves the right to change, rename, or remove this interface at any time.
VTIEnvironment
Field Summary | |
static double |
defaultEstimatedCost
A useful constant: The default estimated cost of instantiating and iterating throught a VTI. |
static double |
defaultEstimatedRowCount
A useful constant: the default estimated number of rows returned by a VTI. |
Method Summary | |
double |
getEstimatedCostPerInstantiation(VTIEnvironment vtiEnvironment)
Get the estimated cost for a single instantiation of a VTI. |
double |
getEstimatedRowCount(VTIEnvironment vtiEnvironment)
Get the estimated row count for a single scan of a VTI. |
boolean |
supportsMultipleInstantiations(VTIEnvironment vtiEnvironment)
Find out if the ResultSet of the VTI can be instantiated multiple times. |
Field Detail |
public static final double defaultEstimatedRowCount
public static final double defaultEstimatedCost
Method Detail |
public double getEstimatedRowCount(VTIEnvironment vtiEnvironment) throws java.sql.SQLException
vtiEnvironment
- The VTIEnvironment.
java.sql.SQLException
- thrown if the costing fails.public double getEstimatedCostPerInstantiation(VTIEnvironment vtiEnvironment) throws java.sql.SQLException
vtiEnvironment
- The VTIEnvironment.
java.sql.SQLException
- thrown if the costing fails.public boolean supportsMultipleInstantiations(VTIEnvironment vtiEnvironment) throws java.sql.SQLException
vtiEnvironment
- The VTIEnvironment.
java.sql.SQLException
- thrown if the costing fails.
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