iterator
Class Iterator

java.lang.Object
  iterator.Iterator

All Implemented Interfaces:

Flags

Direct Known Subclasses:

DuplElim, FileScan, NestedLoopsJoins, Sort, SortMerge

public abstract class Iterator

extends java.lang.Object

implements Flags

All the relational operators and access methods are iterators.

Field Summary

boolean

closeFlag a flag to indicate whether this iterator has been closed.

Fields inherited from interface global.Flags

DEBUG, TEST

Constructor Summary

Iterator()

Method Summary

abstract void	close()
void	free_buffer_pages(int n_pages, PageId[] PageIds) free all the buffer pages we requested earlier.
void	get_buffer_pages(int n_pages, PageId[] PageIds, byte[][] bufs) tries to get n_pages of buffer space
abstract Tuple	get_next() abstract method, every subclass must implement it.

Methods inherited from class java.lang.Object

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

Field Detail

closeFlag

public boolean closeFlag

a flag to indicate whether this iterator has been closed. it is set to true the first time the close() function is called. multiple calls to the close() function will not be a problem.

Constructor Detail

Iterator

public Iterator()

Method Detail

get_next

public abstract Tuple get_next()
                        throws java.io.IOException,
                               JoinsException,
                               index.IndexException,
                               InvalidTupleSizeException,
                               InvalidTypeException,
                               PageNotReadException,
                               TupleUtilsException,
                               PredEvalException,
                               SortException,
                               LowMemException,
                               UnknowAttrType,
                               UnknownKeyTypeException,
                               java.lang.Exception

abstract method, every subclass must implement it.

Returns:

the result tuple

Throws:

java.io.IOException - I/O errors

JoinsException - some join exception

index.IndexException - exception from super class

InvalidTupleSizeException - invalid tuple size

InvalidTypeException - tuple type not valid

PageNotReadException - exception from lower layer

TupleUtilsException - exception from using tuple utilities

PredEvalException - exception from PredEval class

SortException - sort exception

LowMemException - memory error

UnknowAttrType - attribute type unknown

UnknownKeyTypeException - key type unknown

java.lang.Exception - other exceptions

close

public abstract void close()
                    throws java.io.IOException,
                           JoinsException,
                           SortException,
                           index.IndexException

Throws:

java.io.IOException - I/O errors

JoinsException - some join exception

index.IndexException - exception from Index class

SortException - exception Sort class

get_buffer_pages

public void get_buffer_pages(int n_pages,
                             PageId[] PageIds,
                             byte[][] bufs)
                      throws IteratorBMException

tries to get n_pages of buffer space

Parameters:

n_pages - the number of pages

PageIds - the corresponding PageId for each page

bufs - the buffer space

Throws:

IteratorBMException - exceptions from bufmgr layer

free_buffer_pages

public void free_buffer_pages(int n_pages,
                              PageId[] PageIds)
                       throws IteratorBMException

free all the buffer pages we requested earlier. should be called in the destructor

Parameters:

n_pages - the number of pages

PageIds - the corresponding PageId for each page

Throws:

IteratorBMException - exception from bufmgr class