Class HeapCompressScan

java.lang.Object

org.apache.derby.impl.store.access.conglomerate.GenericController

org.apache.derby.impl.store.access.conglomerate.GenericScanController

org.apache.derby.impl.store.access.heap.HeapScan

org.apache.derby.impl.store.access.heap.HeapCompressScan

All Implemented Interfaces:

ScanManager, GenericScanController, GroupFetchScanController, RowCountable, ScanController

class HeapCompressScan
extends HeapScan

A heap scan object represents an instance of a scan on a heap conglomerate.

Field Summary

Fields

Modifier and Type	Field	Description
private long	pagenum_to_start_moving_rows	Fields of HeapScan

Fields inherited from class GenericScanController

rowLocationsInvalidated, SCAN_DONE, SCAN_HOLD_INIT, SCAN_HOLD_INPROGRESS, SCAN_INIT, SCAN_INPROGRESS, scan_position, stat_numpages_visited, stat_numrows_qualified, stat_numrows_visited

Fields inherited from class GenericController

open_conglom

Fields inherited from interface ScanController

GE, GT, NA

Constructor Summary

Constructors

Constructor	Description
HeapCompressScan()	The only constructor for a HeapCompressScan returns a scan in the closed state, the caller must call open.

Method Summary

Modifier and Type	Method	Description
int	fetchNextGroup(DataValueDescriptor[][] row_array, RowLocation[] old_rowloc_array, RowLocation[] new_rowloc_array)	Protected override implementation of routines in GenericController class:
private int	fetchRowsForCompress(DataValueDescriptor[][] row_array, RowLocation[] oldrowloc_array, RowLocation[] newrowloc_array)	Fetch the next N rows from the table.
private void	positionAfterThisPage(RowPosition pos)	Set scan position to just after current page.
protected void	positionAtResumeScan(RowPosition pos)	Reposition the scan upon entering the fetchRows loop.
protected void	positionAtStartForForwardScan(RowPosition pos)	Move the scan from SCAN_INIT to SCAN_INPROGRESS.

Methods inherited from class HeapScan

fetchLocation, fetchNext, fetchNextGroup, getScanInfo, makeRowLocation, next, positionAtRowLocation, queueDeletePostCommitWork, reopenScanByRowLocation, setRowLocationArray, setRowLocationArray

Methods inherited from class GenericScanController

allocateScanPosition, close, closeForEndTransaction, delete, didNotQualify, doesCurrentPositionQualify, fetch, fetchRows, fetchSet, fetchWithoutQualify, getNumPagesVisited, getNumRowsQualified, getNumRowsVisited, getQualifier, getScanColumnList, getScanPosition, getScanState, getStartKeyValue, getStartSearchOperator, getStopKeyValue, getStopSearchOperator, init, isCurrentPositionDeleted, isHeldAfterCommit, positionAtDoneScan, positionAtInitScan, positionAtNextPage, reopenAfterEndTransaction, reopenScan, reopenScanByRecordHandle, replace, setScanPosition, setScanState

Methods inherited from class GenericController

checkConsistency, debugConglomerate, getEstimatedRowCount, getInternalTablePropertySet, getOpenConglom, getRowPositionFromRowLocation, getSpaceInfo, getTableProperties, init, isKeyed, isTableLocked, newRowLocationTemplate, setEstimatedRowCount

Methods inherited from class Object

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

Methods inherited from interface GenericScanController

close, isKeyed, isTableLocked, newRowLocationTemplate, reopenScan

Methods inherited from interface RowCountable

getEstimatedRowCount, setEstimatedRowCount

Methods inherited from interface ScanController

delete, didNotQualify, doesCurrentPositionQualify, fetch, fetchWithoutQualify, isCurrentPositionDeleted, isHeldAfterCommit, replace

Methods inherited from interface ScanManager

closeForEndTransaction, fetchSet

Field Details

pagenum_to_start_moving_rows

private long pagenum_to_start_moving_rows

Fields of HeapScan

Constructor Details

HeapCompressScan

public HeapCompressScan()

The only constructor for a HeapCompressScan returns a scan in the closed state, the caller must call open.

Method Details

fetchNextGroup

public int fetchNextGroup(DataValueDescriptor[][] row_array,
 RowLocation[] old_rowloc_array,
 RowLocation[] new_rowloc_array)
                   throws StandardException

Protected override implementation of routines in GenericController class:

Specified by:

fetchNextGroup in interface GroupFetchScanController

Overrides:

fetchNextGroup in class HeapScan

Throws:

StandardException

fetchRowsForCompress

private int fetchRowsForCompress(DataValueDescriptor[][] row_array,
 RowLocation[] oldrowloc_array,
 RowLocation[] newrowloc_array)
                          throws StandardException

Fetch the next N rows from the table.

Utility routine used by both fetchSet() and fetchNextGroup().

Throws:

StandardException - Standard exception policy.

positionAtResumeScan

protected void positionAtResumeScan(RowPosition pos)
                             throws StandardException

Reposition the scan upon entering the fetchRows loop.

Called upon entering fetchRows() while in the SCAN_INPROGRESS state. Do work necessary to look at rows in the current page of the scan.

The default implementation uses a record handle to maintain a scan position. It will get the latch again on the current scan position and set the slot to the current record handle.

Overrides:

positionAtResumeScan in class GenericScanController

Throws:

StandardException - Standard exception policy.

positionAtStartForForwardScan

protected void positionAtStartForForwardScan(RowPosition pos)
                                      throws StandardException

Move the scan from SCAN_INIT to SCAN_INPROGRESS.

This routine is called to move the scan from SCAN_INIT to SCAN_INPROGRESS. Upon return from this routine it is expected that scan_position is set such that calling the generic scan loop will reach the first row of the scan. Note that this usually means setting the scan_postion to one before the 1st row to be returned.

Overrides:

positionAtStartForForwardScan in class GenericScanController

Throws:

StandardException - Standard exception policy.

positionAfterThisPage

private void positionAfterThisPage(RowPosition pos)
                            throws StandardException

Set scan position to just after current page.

Used to set the position of the scan if a record handle is not avaliable. In this case current_rh will be set to null, and current_pageno will be set to the current page number. On resume of the scan, the scan will be set to just before the first row returned form a getNextPage(current_pageno) call.

A positionAtResumeScan(scan_position) is necessary to continue the scan after this call.

Throws:

StandardException - Standard exception policy.