HashEquiJoin

java.lang.Object
- simpledb.Operator
- - simpledb.HashEquiJoin

All Implemented Interfaces:

java.io.Serializable, DbIterator
```
public class HashEquiJoin
extends Operator
```
The Join operator implements the relational join operation.

See Also:

Serialized Form

Field Summary

Fields
Modifier and Type	Field and Description
`private DbIterator`	`child1`
`private DbIterator`	`child2`
`private TupleDesc`	`comboTD`
`(package private) java.util.Iterator<Tuple>`	`listIt`
`(package private) java.util.HashMap<java.lang.Object,java.util.ArrayList<Tuple>>`	`map`
`static int`	`MAP_SIZE`
`private JoinPredicate`	`pred`
`private static long`	`serialVersionUID`
`private Tuple`	`t1`
`private Tuple`	`t2`

Constructor Summary

Constructors
Constructor and Description

HashEquiJoin(JoinPredicate p, DbIterator child1, DbIterator child2)
Constructor.

Constructors
Constructor and Description
`HashEquiJoin(JoinPredicate p, DbIterator child1, DbIterator child2)` Constructor.

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`close()` Closes this iterator.
`protected Tuple`	`fetchNext()` Returns the next Tuple in the iterator, or null if the iteration is finished.
`DbIterator[]`	`getChildren()`
`java.lang.String`	`getJoinField1Name()`
`java.lang.String`	`getJoinField2Name()`
`JoinPredicate`	`getJoinPredicate()`
`TupleDesc`	`getTupleDesc()` Returns the TupleDesc associated with this DbIterator.
`private boolean`	`loadMap()`
`void`	`open()` Opens the iterator.
`private Tuple`	`processList()` Returns the next tuple generated by the join, or null if there are no more tuples.
`void`	`rewind()` Resets the iterator to the start.
`void`	`setChildren(DbIterator[] children)` Set the children(child) of this operator.

Methods inherited from class simpledb.Operator
getEstimatedCardinality, hasNext, next, setEstimatedCardinality

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - serialVersionUID
```
private static final long serialVersionUID
```
    See Also:
    
    Constant Field Values
  - pred
```
private JoinPredicate pred
```
  - child1
```
private DbIterator child1
```
  - child2
```
private DbIterator child2
```
  - comboTD
```
private TupleDesc comboTD
```
  - t1
```
private transient Tuple t1
```
  - t2
```
private transient Tuple t2
```
  - map
```
java.util.HashMap<java.lang.Object,java.util.ArrayList<Tuple>> map
```
  - MAP_SIZE
```
public static final int MAP_SIZE
```
    See Also:
    
    Constant Field Values
  - listIt
```
transient java.util.Iterator<Tuple> listIt
```
- Constructor Detail
  - HashEquiJoin
```
public HashEquiJoin(JoinPredicate p,
                    DbIterator child1,
                    DbIterator child2)
```
    Constructor. Accepts to children to join and the predicate to join them on
    
    Parameters:
    
    p - The predicate to use to join the children
    
    child1 - Iterator for the left(outer) relation to join
    
    child2 - Iterator for the right(inner) relation to join
- Method Detail
  - getJoinPredicate
```
public JoinPredicate getJoinPredicate()
```
  - getTupleDesc
```
public TupleDesc getTupleDesc()
```
    Description copied from interface: DbIterator
    
    Returns the TupleDesc associated with this DbIterator.
    
    Specified by:
    
    getTupleDesc in interface DbIterator
    
    Specified by:
    
    getTupleDesc in class Operator
    
    Returns:
    
    return the TupleDesc of the output tuples of this operator
  - getJoinField1Name
```
public java.lang.String getJoinField1Name()
```
  - getJoinField2Name
```
public java.lang.String getJoinField2Name()
```
  - loadMap
```
private boolean loadMap()
                 throws DbException,
                        TransactionAbortedException
```
    Throws:
    
    DbException
    
    TransactionAbortedException
  - open
```
public void open()
          throws DbException,
                 java.util.NoSuchElementException,
                 TransactionAbortedException
```
    Description copied from interface: DbIterator
    
    Opens the iterator. This must be called before any of the other methods.
    
    Specified by:
    
    open in interface DbIterator
    
    Overrides:
    
    open in class Operator
    
    Throws:
    
    DbException - when there are problems opening/accessing the database.
    
    java.util.NoSuchElementException
    
    TransactionAbortedException
  - close
```
public void close()
```
    Description copied from class: Operator
    
    Closes this iterator. If overridden by a subclass, they should call super.close() in order for Operator's internal state to be consistent.
    
    Specified by:
    
    close in interface DbIterator
    
    Overrides:
    
    close in class Operator
  - rewind
```
public void rewind()
            throws DbException,
                   TransactionAbortedException
```
    Description copied from interface: DbIterator
    
    Resets the iterator to the start.
    
    Throws:
    
    DbException - when rewind is unsupported.
    
    TransactionAbortedException
  - processList
```
private Tuple processList()
                   throws TransactionAbortedException,
                          DbException
```
    Returns the next tuple generated by the join, or null if there are no more tuples. Logically, this is the next tuple in r1 cross r2 that satisfies the join predicate. There are many possible implementations; the simplest is a nested loops join.
    Note that the tuples returned from this particular implementation of Join are simply the concatenation of joining tuples from the left and right relation. Therefore, there will be two copies of the join attribute in the results. (Removing such duplicate columns can be done with an additional projection operator if needed.)
    For example, if one tuple is {1,2,3} and the other tuple is {1,5,6}, joined on equality of the first column, then this returns {1,2,3,1,5,6}.
    
    Returns:
    
    The next matching tuple.
    
    Throws:
    
    TransactionAbortedException
    
    DbException
    
    See Also:
    
    JoinPredicate.filter(simpledb.Tuple, simpledb.Tuple)
  - fetchNext
```
protected Tuple fetchNext()
                   throws TransactionAbortedException,
                          DbException
```
    Description copied from class: Operator
    
    Returns the next Tuple in the iterator, or null if the iteration is finished. Operator uses this method to implement both next and hasNext.
    
    Specified by:
    
    fetchNext in class Operator
    
    Returns:
    
    the next Tuple in the iterator, or null if the iteration is finished.
    
    Throws:
    
    TransactionAbortedException
    
    DbException
  - getChildren
```
public DbIterator[] getChildren()
```
    Specified by:
    
    getChildren in class Operator
    
    Returns:
    
    return the children DbIterators of this operator. If there is only one child, return an array of only one element. For join operators, the order of the children is not important. But they should be consistent among multiple calls.
  - setChildren
```
public void setChildren(DbIterator[] children)
```
    Description copied from class: Operator
    
    Set the children(child) of this operator. If the operator has only one child, children[0] should be used. If the operator is a join, children[0] and children[1] should be used.
    
    Specified by:
    
    setChildren in class Operator
    
    Parameters:
    
    children - the DbIterators which are to be set as the children(child) of this operator

Class HashEquiJoin

Field Summary

Constructor Summary

Method Summary

Methods inherited from class simpledb.Operator

Methods inherited from class java.lang.Object

Field Detail

serialVersionUID

pred

child1

child2

comboTD

t1

t2

map

MAP_SIZE

listIt

Constructor Detail

HashEquiJoin

Method Detail

getJoinPredicate

getTupleDesc

getJoinField1Name

getJoinField2Name

loadMap

open

close

rewind

processList

fetchNext

getChildren

setChildren