Class BTreeForwardScan

java.lang.Object

org.apache.derby.impl.store.access.btree.OpenBTree

org.apache.derby.impl.store.access.btree.BTreeScan

org.apache.derby.impl.store.access.btree.BTreeForwardScan

All Implemented Interfaces:

ScanManager, GenericScanController, GroupFetchScanController, RowCountable, ScanController

Direct Known Subclasses:

B2IForwardScan

public class BTreeForwardScan
extends BTreeScan

A b-tree scan controller corresponds to an instance of an open b-tree scan.

Concurrency Notes

The concurrency rules are derived from OpenBTree.

See Also:

• OpenBTree

Field Summary

Fields inherited from class BTreeScan

fetchNext_one_slot_array, init_fetchDesc, init_forUpdate, init_hold, init_lock_fetch_desc, init_qualifier, init_rawtran, init_scanColumnList, init_startKeyValue, init_startSearchOperator, init_stopKeyValue, init_stopSearchOperator, init_template, init_useUpdateLocks, lock_operation, SCAN_DONE, SCAN_HOLD_INIT, SCAN_HOLD_INPROGRESS, SCAN_INIT, SCAN_INPROGRESS, scan_position, scan_state, stat_numdeleted_rows_visited, stat_numpages_visited, stat_numrows_qualified, stat_numrows_visited

Fields inherited from class OpenBTree

btree_undo, container, err_containerid, init_lock_level, init_open_user_scans, runtime_mem

Fields inherited from interface ScanController

GE, GT, NA

Constructor Summary

Constructors

Constructor	Description
BTreeForwardScan()

Method Summary

Modifier and Type	Method	Description
protected int	fetchRows(BTreeRowPosition pos, DataValueDescriptor[][] row_array, RowLocation[] rowloc_array, BackingStoreHashtable hash_table, long max_rowcnt, int[] key_column_numbers)	Fetch the next N rows from the table.
protected void	positionAtStartPosition(BTreeRowPosition pos)	Position scan at "start" position.

Methods inherited from class BTreeScan

close, closeForEndTransaction, delete, didNotQualify, doesCurrentPositionQualify, fetch, fetchLocation, fetchNext, fetchNextGroup, fetchNextGroup, fetchSet, fetchWithoutQualify, getCurrentRecordHandleForDebugging, getScanInfo, init, isCurrentPositionDeleted, isEmpty, isHeldAfterCommit, isKeyed, newRowLocationTemplate, next, positionAtDoneScan, positionAtDoneScanFromClose, positionAtNextPage, positionAtPreviousPage, positionAtRowLocation, positionAtStartForForwardScan, process_qualifier, reopenScan, reopenScanByRowLocation, replace, reposition, savePositionAndReleasePage, savePositionAndReleasePage, toString

Methods inherited from class OpenBTree

checkConsistency, debugConglomerate, getColumnSortOrderInfo, getConglomerate, getContainer, getContainerHandle, getEstimatedRowCount, getHeight, getHold, getLockingPolicy, getLockLevel, getOpenMode, getRawTran, getRuntimeMem, getSpaceInfo, getXactMgr, init, isClosed, isIndexableRowConsistent, isTableLocked, reopen, setEstimatedRowCount, setLockingPolicy, test_errors

Methods inherited from class Object

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

Methods inherited from interface GenericScanController

isTableLocked

Methods inherited from interface RowCountable

getEstimatedRowCount, setEstimatedRowCount

Constructor Details

BTreeForwardScan

public BTreeForwardScan()

Method Details

positionAtStartPosition

protected void positionAtStartPosition(BTreeRowPosition pos)
                                throws StandardException

Position scan at "start" position.

Positions the scan to the slot just before the first record to be returned from the scan. Returns the start page latched, and sets "current_slot" to the slot number.

Specified by:

positionAtStartPosition in class BTreeScan

Throws:

StandardException - Standard exception policy.

fetchRows

protected int fetchRows(BTreeRowPosition pos,
 DataValueDescriptor[][] row_array,
 RowLocation[] rowloc_array,
 BackingStoreHashtable hash_table,
 long max_rowcnt,
 int[] key_column_numbers)
                 throws StandardException

Fetch the next N rows from the table.

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

Specified by:

fetchRows in class BTreeScan

Throws:

StandardException - Standard exception policy.