relop
Class Predicate

java.lang.Object
  relop.Predicate

public class Predicate
extends java.lang.Object

Internal representation of simple SQL expressions. Operators are referenced by constants in global.AttrOperator, and operands can be constants or field numbers (i.e. if referring to an attribute).

Field Summary

protected java.lang.Object	left Left operand.
protected int	ltype Type of left operand.
protected int	oper The operator.
protected java.lang.Object	right Right operand.
protected int	rtype Type of right operand.

Constructor Summary

Predicate(int oper, int ltype, java.lang.Object left, int rtype, java.lang.Object right)
Constructs a predicate, given the expression.

Method Summary

boolean	evaluate(Tuple tuple) Evaluates the predicate on the given tuple and returns true if it passes.
protected java.lang.String	opString(int type, java.lang.Object operand) Returns a string representation of an operand.
java.lang.String	toString() Returns a string representation of the Predicate.
boolean	validate(Schema schema) Validates AttrType.COLNAME operands against the given schema.

Methods inherited from class java.lang.Object

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

Field Detail

oper

protected int oper

The operator.

ltype

protected int ltype

Type of left operand.

left

protected java.lang.Object left

Left operand.

rtype

protected int rtype

Type of right operand.

right

protected java.lang.Object right

Right operand.

Constructor Detail

Predicate

public Predicate(int oper,
                 int ltype,
                 java.lang.Object left,
                 int rtype,
                 java.lang.Object right)

Constructs a predicate, given the expression.

Parameters:

oper - AttrOperator constant

ltype - AttrType of the field

left - operand value, field number, or column name

rtype - AttrType of the field

right - operand value, field number, or column name

Method Detail

validate

public boolean validate(Schema schema)

Validates AttrType.COLNAME operands against the given schema.

Returns:

true if the predicate is valid, false otherwise

evaluate

public boolean evaluate(Tuple tuple)

Evaluates the predicate on the given tuple and returns true if it passes.

Throws:

java.lang.IllegalStateException - if member data lead to an invalid operation

toString

public java.lang.String toString()

Returns a string representation of the Predicate.

Overrides:

toString in class java.lang.Object

opString

protected java.lang.String opString(int type,
                                    java.lang.Object operand)

Returns a string representation of an operand.