heap
Class HeapScan

java.lang.Object
  heap.HeapScan

All Implemented Interfaces:

GlobalConst

public class HeapScan
extends java.lang.Object
implements GlobalConst

A HeapScan object is created only through the function openScan() in the HeapFile class. It supports the getNext interface which will simply retrieve the next record in the file.

Field Summary

Fields inherited from interface global.GlobalConst

EMPTY_SLOT, FIRST_PAGEID, INVALID_PAGEID, MAX_COLSIZE, MAX_TUPSIZE, NAME_MAXLEN, PAGE_SIZE, PIN_DISKIO, PIN_MEMCPY, UNPIN_CLEAN, UNPIN_DIRTY

Constructor Summary

protected

HeapScan(HeapFile hf) Constructs a file scan by pinning the directoy header page and initializing iterator fields.

Method Summary

void	close() Closes the file scan, releasing any pinned pages.
protected void	finalize() Called by the garbage collector when there are no more references to the object; closes the scan if it's still open.
byte[]	getNext(RID rid) Gets the next record in the file scan.
boolean	hasNext() Returns true if there are more records to scan, false otherwise.

Methods inherited from class java.lang.Object

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

Constructor Detail

HeapScan

protected HeapScan(HeapFile hf)

Constructs a file scan by pinning the directoy header page and initializing iterator fields.

Method Detail

finalize

protected void finalize()
                 throws java.lang.Throwable

Called by the garbage collector when there are no more references to the object; closes the scan if it's still open.

Overrides:

finalize in class java.lang.Object

Throws:

java.lang.Throwable

close

public void close()

Closes the file scan, releasing any pinned pages.

hasNext

public boolean hasNext()

Returns true if there are more records to scan, false otherwise.

getNext

public byte[] getNext(RID rid)

Gets the next record in the file scan.

Parameters:

rid - output parameter that identifies the returned record

Throws:

java.lang.IllegalStateException - if the scan has no more elements