org.eigenbase.runtime
Class NestedLoopCalcTupleIter

java.lang.Object
  org.eigenbase.runtime.CalcTupleIter
      org.eigenbase.runtime.NestedLoopCalcTupleIter

All Implemented Interfaces:

TupleIter, ClosableAllocation

public abstract class NestedLoopCalcTupleIter
extends CalcTupleIter

NestedLoopCalcTupleIter is a specialization of CalcTupleIter for use in implementing nested loop inner joins over iterators.

REVIEW jvs 20-Mar-2004: I have parameterized this to handle inner and left outer joins, as well as one-to-many and many-to-one variants. This comes at the price of some efficiency. It would probably be better to write specialized bases for each purpose.

Version:

$Id: //open/dev/farrago/src/org/eigenbase/runtime/NestedLoopCalcTupleIter.java#9 $

Author:

John V. Sichi

Nested Class Summary

Nested classes/interfaces inherited from interface org.eigenbase.runtime.TupleIter

TupleIter.NoDataReason, TupleIter.TimeoutException

Field Summary

private boolean	isLeftOuter
private boolean	isOpen
protected Object	leftObj
private boolean	needNullRow
protected Object	rightIterator
protected Object	rightObj

Fields inherited from class org.eigenbase.runtime.CalcTupleIter

inputIterator

Fields inherited from interface org.eigenbase.runtime.TupleIter

EMPTY_ITERATOR

Constructor Summary

protected

NestedLoopCalcTupleIter(TupleIter leftIterator, boolean isLeftOuter)

Method Summary

protected abstract Object	calcJoinRow() Method to be implemented by subclasses to either calculate the next joined row based on current values of leftObj and rightObj, or else to filter out this combination.
protected Object	calcRightNullRow() Method to be implemented by subclasses to calculate a mismatch row in a left outer join.
Object	fetchNext() Returns the next element in the iteration.
protected abstract Object	getNextRightIterator() Method to be implemented by subclasses to determine next right-hand iterator based on current value of leftObj.
protected void	open() Method which can be overridden by subclasses to carry out post-constructor initialization.

Methods inherited from class org.eigenbase.runtime.CalcTupleIter

closeAllocation, restart, setTimeout

Methods inherited from class java.lang.Object

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

Field Detail

rightIterator

protected Object rightIterator

leftObj

protected Object leftObj

rightObj

protected Object rightObj

isOpen

private boolean isOpen

isLeftOuter

private boolean isLeftOuter

needNullRow

private boolean needNullRow

Constructor Detail

NestedLoopCalcTupleIter

protected NestedLoopCalcTupleIter(TupleIter leftIterator,
                                  boolean isLeftOuter)

Method Detail

fetchNext

public Object fetchNext()

Description copied from interface: TupleIter

Returns the next element in the iteration. If there is no next value, it returns a value from the TupleIter.NoDataReason enumeration indicating why no data was returned.

If this method returns TupleIter.NoDataReason.END_OF_DATA, no further data will be returned by this iterator unless TupleIter.restart() is called.

If this method returns TupleIter.NoDataReason.UNDERFLOW, no data is currently available, but may be come available in the future. It is possible for consecutive calls to return UNDERFLOW and then END_OF_DATA.

The object returned by this method may be re-used for each subsequent call to fetchNext(). In other words, callers must either make certain that the returned value is no longer needed or is copied before any subsequent calls to fetchNext().

Returns:

the next element in the iteration, or an instance of TupleIter.NoDataReason.

open

protected void open()

Method which can be overridden by subclasses to carry out post-constructor initialization.

getNextRightIterator

protected abstract Object getNextRightIterator()

Method to be implemented by subclasses to determine next right-hand iterator based on current value of leftObj. For a many-to-one join, this can return the right-hand object directly instead of a TupleIter, but should return TupleIter.EMPTY_ITERATOR for a mismatch.

Returns:

iterator or object

calcJoinRow

protected abstract Object calcJoinRow()

Method to be implemented by subclasses to either calculate the next joined row based on current values of leftObj and rightObj, or else to filter out this combination.

Returns:

row or null for filtered oute

calcRightNullRow

protected Object calcRightNullRow()

Method to be implemented by subclasses to calculate a mismatch row in a left outer join. Inner joins can use the default (return null) because it will never be called.

Returns:

row with all right fields set to null