simpledb

Class Predicate

java.lang.Object

simpledb.Predicate

All Implemented Interfaces:

java.io.Serializable

public class Predicate
extends java.lang.Object
implements java.io.Serializable

Predicate compares tuples to a specified Field value.

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Predicate.Op Constants used for return codes in Field.compare

Field Summary

Fields

Modifier and Type	Field and Description
private static long	serialVersionUID

Constructor Summary

Constructors

Constructor and Description
Predicate(int field, Predicate.Op op, Field operand) Constructor.

Method Summary

Methods

Modifier and Type	Method and Description
boolean	filter(Tuple t) Compares the field number of t specified in the constructor to the operand field specified in the constructor using the operator specific in the constructor.
int	getField()
Predicate.Op	getOp()
Field	getOperand()
java.lang.String	toString() Returns something useful, like "f = field_id op = op_string operand = operand_string

Methods inherited from class java.lang.Object

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

Field Detail

serialVersionUID

private static final long serialVersionUID

See Also:

Constant Field Values

Constructor Detail

Predicate

public Predicate(int field,
         Predicate.Op op,
         Field operand)

Constructor.

Parameters:

field - field number of passed in tuples to compare against.

op - operation to use for comparison

operand - field value to compare passed in tuples to

Method Detail

getField

public int getField()

Returns:

the field number

getOp

public Predicate.Op getOp()

Returns:

the operator

getOperand

public Field getOperand()

Returns:

the operand

filter

public boolean filter(Tuple t)

Compares the field number of t specified in the constructor to the operand field specified in the constructor using the operator specific in the constructor. The comparison can be made through Field's compare method.

Parameters:

t - The tuple to compare against

Returns:

true if the comparison is true, false otherwise.

toString

public java.lang.String toString()

Returns something useful, like "f = field_id op = op_string operand = operand_string

Overrides:

toString in class java.lang.Object