net.sf.saffron.opt
Class RuleOperand

java.lang.Object
  |
  +--net.sf.saffron.opt.RuleOperand

All Implemented Interfaces:

Walkable

public class RuleOperand

extends Object

implements Walkable

A RuleOperand determines whether a VolcanoRule can be applied to a particular expression.

For example, the rule to pull a filter up from the left side of a join takes operands: (Join (Filter) (Any)).

Note that children means different things if it is empty or it is null: (Join (Filter ()) (Any)) means that, to match the rule, Filter must have no operands.

Field Summary

private RuleOperand[]	children
private Class	clazz
private CallingConvention	convention
(package private) static RuleOperand[]	noOperands
(package private) int	ordinalInParent
(package private) int	ordinalInRule
(package private) RuleOperand	parent
(package private) VolcanoRule	rule
(package private) int[]	solveOrder

Constructor Summary

RuleOperand(Class clazz, CallingConvention convention, RuleOperand[] children)
Creates an operand which matches any CallingConvention.

RuleOperand(Class clazz, RuleOperand[] children)
Creates an operand which matches any CallingConvention.

Method Summary

Object[]	getChildren() returns an array of the object's children.
boolean	matches(SaffronRel rel) Returns whether a relational expression matches this operand.

Methods inherited from class java.lang.Object

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

Field Detail

noOperands

static final RuleOperand[] noOperands

parent

RuleOperand parent

rule

VolcanoRule rule

solveOrder

int[] solveOrder

ordinalInParent

int ordinalInParent

ordinalInRule

int ordinalInRule

convention

private final CallingConvention convention

clazz

private final Class clazz

children

private final RuleOperand[] children

Constructor Detail

RuleOperand

public RuleOperand(Class clazz,
                   RuleOperand[] children)

Creates an operand which matches any CallingConvention.

Pre-condition:

clazz != null

RuleOperand

public RuleOperand(Class clazz,
                   CallingConvention convention,
                   RuleOperand[] children)

Creates an operand which matches any CallingConvention.

Pre-condition:

clazz != null

Method Detail

getChildren

public Object[] getChildren()

Description copied from interface: Walkable

returns an array of the object's children. Those which are not Walkable are ignored.

Specified by:

getChildren in interface Walkable

matches

public boolean matches(SaffronRel rel)

Returns whether a relational expression matches this operand. It must be of the right class and calling convention.