simpledb
Class Predicate

java.lang.Object
  simpledb.Predicate

public class Predicate
extends java.lang.Object

Predicate compares tuples to a specified Field value.

Nested Class Summary

static class

Predicate.Op Constants used for return codes in Field.compare

Constructor Summary

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

Method Summary

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.
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

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

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