net.sf.saffron.oj.rel
Interface JavaRel

All Known Implementing Classes:

JavaNestedLoopJoinRel, JavaOneRowRel, JavaProjectRel

public interface JavaRel

A relational expression of the Java calling convention.

Objects which implement this interface must (a) extend SaffronRel, and (b) return CallingConvention.JAVA from their SaffronRel.getConvention() method

Since:

Nov 22, 2003$

Version:

$Id: $

Author:

jhyde$

Method Summary

Expression

implementSelf(RelImplementor implementor) Returns a Java expression which yields the current row of this relational expression.

Method Detail

implementSelf

public Expression implementSelf(RelImplementor implementor)

Returns a Java expression which yields the current row of this relational expression. This method is called by the RelImplementor the first time a piece of Java code wants to refer to this relation. The implementor then uses this expression to initialize a variable.

If no code needs to refer to this relation, then the expression is never generated. This prevents generating useless code like

Dummy_12f614.Ojp_1 oj_var8 = new Dummy_12f614.Ojp_1();

.

If a relational expression has one input relational expression which has the same row type, you may be able to share its variable. Call Implementor#bind(Rel,Rel) to do this.

See Also:

RelImplementor.bind(SaffronRel,SaffronRel)