saffron.rel.convert
Class ConverterRule

java.lang.Object
  |
  +--saffron.opt.Rule
        |
        +--saffron.rel.convert.ConverterRule

Direct Known Subclasses:

Aggregate.ConvertToJavaRule, Distinct.ConvertDistinctToJavaRule, FactoryConverterRule, Filter.ConvertToJavaRule, Filter.ConvertToPlanRule, Join.ConvertToJavaRule, Join.ConvertToPlanRule, OneRow.OneRowToJavaRule, Project.ConvertToJavaRule, Project.ConvertToPlanRule, TableAccess.ConvertToJavaRule, Union.ConvertToIteratorRule, Union.ConvertToJavaRule

public abstract class ConverterRule

extends Rule

Abstract base class for a rule which converts from one calling convention to another without changing semantics.

Since:

May 5, 2003

Version:

$Id: //open/saffron/src/main/saffron/rel/convert/ConverterRule.java#6 $

Author:

jhyde

Field Summary

CallingConvention	inConvention
CallingConvention	outConvention

Fields inherited from class saffron.opt.Rule

description, planner

Constructor Summary

ConverterRule(Class clazz, CallingConvention in, CallingConvention out, String description)
Creates a ConverterRule

Method Summary

abstract Rel	convert(Rel rel)
CallingConvention	getOutConvention() Returns the calling convention of the result of firing this rule, null if not known.
boolean	isGuaranteed() Returns true if this rule can convert any relational expression of the input convention.
void	onMatch(RuleCall call) This method is called every time the rule matches.

Methods inherited from class saffron.opt.Rule

convert, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

inConvention

public final CallingConvention inConvention

outConvention

public final CallingConvention outConvention

Constructor Detail

ConverterRule

public ConverterRule(Class clazz,
                     CallingConvention in,
                     CallingConvention out,
                     String description)

Creates a ConverterRule

Pre-condition:

in != null, out != null

Method Detail

getOutConvention

public CallingConvention getOutConvention()

Description copied from class: Rule

Returns the calling convention of the result of firing this rule, null if not known.

Overrides:

getOutConvention in class Rule

convert

public abstract Rel convert(Rel rel)

isGuaranteed

public boolean isGuaranteed()

Returns true if this rule can convert any relational expression of the input convention.

The union-to-java converter, for example, is not guaranteed, because it only works on unions.

onMatch

public void onMatch(RuleCall call)

Description copied from class: Rule

This method is called every time the rule matches. At the time that this method is called, call.rels holds the set of relational expressions which match the operands to the rule; call.rels[0] is the root expression.

Typically a rule would check that the nodes are valid matches, creates a new expression, then calls back RuleCall.transformTo(saffron.rel.Rel) to register the expression.

Specified by:

onMatch in class Rule