This interface is implemented by a read/write VTI class that wants to control when modifications to the VTI are deferred, or to be notified that a it is to be modified.
An internal api for VTIs to allow VTI's written in terms of the datatype system, e.g.
Support for pushing SQL statement information down into a virtual table.
Interface for Table Functions which can be told which columns need to be fetched plus simple bounds on those columns.
VTICosting is the interface that the query optimizer uses to cost Table Functions.
VTIEnvironment is the state variable created by the optimizer to help it place a Table Function in the join order.
An expression to be pushed into a Table Function so that the Table Function can short-circuit its processing and return fewer rows.
An AND of two Restrictions
A simple comparison of a column to a constant value.
An OR of two Restrictions
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.
An abstract implementation of PreparedStatement (JDBC 3.0) that is useful when writing a read-write (updatable) virtual table interface (VTI).
An abstract implementation of ResultSetMetaData (JDBC 1.2) that is useful when writing a VTI (virtual table interface).
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.
An implementation of the JDBC 3.0 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.
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 () RETURNS TABLE ( employeeId INT, lastName VARCHAR( 50 ), firstName VARCHAR( 50 ), birthday DATE ) LANGUAGE JAVA PARAMETER STYLE DERBY_JDBC_RESULT_SET NO SQL 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.