Apache Derby 10.8

Package org.apache.derby.vti

Support for Table Functions.


Interface Summary
RestrictedVTI Interface for Table Functions which can be told which columns need to be fetched plus simple bounds on those columns.
VTICosting VTICosting is the interface that the query optimizer uses to cost Table Functions.
VTIEnvironment VTIEnvironment is the state variable created by the optimizer to help it place a Table Function in the join order.

Class Summary
Restriction An expression to be pushed into a Table Function so that the Table Function can short-circuit its processing and return fewer rows.
Restriction.AND An AND of two Restrictions
Restriction.ColumnQualifier A simple comparison of a column to a constant value.
Restriction.OR An OR of two Restrictions
StringColumnVTI This is an abstract table function which assumes that all columns are strings and which coerces the strings to reasonable values for various getXXX() methods.
VTITemplate An abstract implementation of ResultSet that is useful when writing table functions, read-only VTIs (virtual table interface), and the ResultSets returned by executeQuery in read-write VTI classes.

Package org.apache.derby.vti Description

Support for Table Functions.

Derby lets you declare functions which return ResultSets. You can then use these function results as tables in your queries. This, in turn, lets you do the following:

Here is an example of how to declare and invoke a Table Function:

CREATE FUNCTION externalEmployees
  employeeId    INT,
  lastName       VARCHAR( 50 ),
  firstName      VARCHAR( 50 ),
  birthday         DATE
EXTERNAL NAME 'com.acme.hrSchema.EmployeesTable.read'

INSERT INTO employees
  SELECT s.*
    FROM TABLE (externalEmployees() ) s;

The Derby optimizer makes some assumptions about these Table Functions:

Based on these assumptions, the optimizer decides where to place the Table Function in the join order. Using the interfaces in this package, you may override the optimizer's guesses and force the optimizer to choose a better join order.

Built on Mon 2011-10-10 14:57:18-0700, from revision 1181258

Apache Derby 10.8 API Documentation - Copyright © 2004,2008 The Apache Software Foundation. All Rights Reserved.