relop
Class HashJoin

java.lang.Object
  relop.Iterator
      relop.HashJoin

public class HashJoin
extends Iterator

Implements the hash-based join algorithm described in section 14.4.3 of the textbook (3rd edition; see pages 463 to 464). HashIndex is used to partition the tuples into buckets, and HashTableDup is used to store a partition in memory during the matching phase.

Field Summary

Fields inherited from class relop.Iterator

schema

Constructor Summary

HashJoin(Iterator left, Iterator right, java.lang.Integer lcol, java.lang.Integer rcol)
Constructs a hash join, given the left and right iterators and which columns to match (relative to their individual schemas).

Method Summary

void	close() Closes the iterator, releasing any resources (i.e.
void	explain(int depth) Gives a one-line explaination of the iterator, repeats the call on any child iterators, and increases the indent depth along the way.
Tuple	getNext() Gets the next tuple in the iteration.
boolean	hasNext() Returns true if there are more tuples, false otherwise.
boolean	isOpen() Returns true if the iterator is open; false otherwise.
void	restart() Restarts the iterator, i.e.

Methods inherited from class relop.Iterator

execute, finalize, indent

Methods inherited from class java.lang.Object

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

Constructor Detail

HashJoin

public HashJoin(Iterator left,
                Iterator right,
                java.lang.Integer lcol,
                java.lang.Integer rcol)

Constructs a hash join, given the left and right iterators and which columns to match (relative to their individual schemas).

Method Detail

explain

public void explain(int depth)

Gives a one-line explaination of the iterator, repeats the call on any child iterators, and increases the indent depth along the way.

Specified by:

explain in class Iterator

restart

public void restart()

Restarts the iterator, i.e. as if it were just constructed.

Specified by:

restart in class Iterator

isOpen

public boolean isOpen()

Returns true if the iterator is open; false otherwise.

Specified by:

isOpen in class Iterator

close

public void close()

Closes the iterator, releasing any resources (i.e. pinned pages).

Specified by:

close in class Iterator

hasNext

public boolean hasNext()

Returns true if there are more tuples, false otherwise.

Specified by:

hasNext in class Iterator

getNext

public Tuple getNext()

Gets the next tuple in the iteration.

Specified by:

getNext in class Iterator

Throws:

java.lang.IllegalStateException - if no more tuples