Overview  Package   Class  Use  Deprecated  Index
Home >> All >> org >> apache >> derby >> impl >> store >> access >> [ conglomerate overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

---

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

java.lang.Object
  org.apache.derby.impl.store.access.conglomerate.GenericController
      org.apache.derby.impl.store.access.conglomerate.GenericScanController

All Implemented Interfaces:

org.apache.derby.iapi.store.access.GenericScanController, org.apache.derby.iapi.store.access.GroupFetchScanController, org.apache.derby.iapi.store.access.RowCountable, org.apache.derby.iapi.store.access.ScanController, org.apache.derby.iapi.store.access.conglomerate.ScanManager

---

public abstract class GenericScanController

extends GenericController

implements org.apache.derby.iapi.store.access.conglomerate.ScanManager

Generic class implementing shared ScanController methods. Logically a scancontroller is used to scan a set of rows that meet some specified qualification. Rows that meet the qualification may be operated upon by the scan to fetch, delete, or replace. The ScanController also supports the notion or "repositioning" the scan, which simply resets the beginning of the scan to a new place, and allows the user to continue from there. This class attempts to abstract out some of the parts of the scan such that maybe multiple access methods can share code, even if they perform parts of the scan wildly differently. Here is how the scan has been broken apart: scan_position - this variable holds the current scan position, it may be extended to provide more information if necessary. scan_state - a scan has 3 possible states: SCAN_INIT, SCAN_INPROGRESS, SCAN_DONE positionAtInitScan() - This routine is called to move the scan to the SCAN_INIT state. It is used both for initialization of the ScanController and by reopenScan(). positionAtStartForForwardScan() - 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. fetchRows() - This routine is the meat of the scan, it moves the scan to the next row, applies necessary qualifiers, and handles group or non-group operations. It moves through rows on a page in order and then moves to the "next" page. positionAtNextPage() - This routine handles moving the scan from the current scan_position to the next page. positionAtDoneScan() - Handle all cleanup associated with moving the scan state from SCAN_INPROGRESS to SCAN_DONE. This may include releasing locks, and setting the state of the scan. This does not close the scan, it allows for a reopenScan() to be called.

---

Field Summary
private  org.apache.derby.iapi.store.raw.FetchDescriptor	init_fetchDesc
private  org.apache.derby.iapi.store.access.Qualifier[][]	init_qualifier
private  org.apache.derby.iapi.services.io.FormatableBitSet	init_scanColumnList           The following group of fields are all basic input parameters which are provided by the calling code when doing a scan.
private  org.apache.derby.iapi.types.DataValueDescriptor[]	init_startKeyValue
private  int	init_startSearchOperator
private  org.apache.derby.iapi.types.DataValueDescriptor[]	init_stopKeyValue
private  int	init_stopSearchOperator
static int	SCAN_DONE
static int	SCAN_HOLD_INIT
static int	SCAN_HOLD_INPROGRESS
static int	SCAN_INIT           Constants of the class
static int	SCAN_INPROGRESS
protected  RowPosition	scan_position           The position for the current scan.
private  int	scan_state           Delay positioning the table at the start position until the first next() call.
protected  int	stat_numpages_visited           Performance counters ...
protected  int	stat_numrows_qualified
protected  int	stat_numrows_visited

 

Fields inherited from class org.apache.derby.impl.store.access.conglomerate.GenericController

open_conglom

 

Fields inherited from interface org.apache.derby.iapi.store.access.ScanController

GE, GT, NA

 

Constructor Summary

GenericScanController()

 

Method Summary
protected  RowPosition	allocateScanPosition()           Create object which represents the scan position.
void	close()           Close the scan.
boolean	closeForEndTransaction(boolean closeHeldScan)           Close scan as part of terminating a transaction.
private  void	closeScan()           Public Methods implementing ScanController:
boolean	delete()           Delete the row at the current position of the scan.
void	didNotQualify()           A call to allow client to indicate that current row does not qualify.
boolean	doesCurrentPositionQualify()           Returns true if the current position of the scan still qualifies under the set of qualifiers passed to the openScan().
void	fetch(org.apache.derby.iapi.types.DataValueDescriptor[] row)           Fetch the (partial) row at the current position of the Scan.
void	fetchLocation(org.apache.derby.iapi.types.RowLocation templateLocation)           Fetch the location of the current position in the scan.
protected  int	fetchRows(org.apache.derby.iapi.types.DataValueDescriptor[][] row_array, org.apache.derby.iapi.types.RowLocation[] rowloc_array, org.apache.derby.iapi.store.access.BackingStoreHashtable hash_table, long max_rowcnt, int[] key_column_numbers)           Fetch the next N rows from the table.
void	fetchSet(long max_rowcnt, int[] key_column_numbers, org.apache.derby.iapi.store.access.BackingStoreHashtable hash_table)           Insert all rows that qualify for the current scan into the input Hash table.
int	getNumPagesVisited()
int	getNumRowsQualified()
int	getNumRowsVisited()
org.apache.derby.iapi.store.access.Qualifier[][]	getQualifier()
org.apache.derby.iapi.services.io.FormatableBitSet	getScanColumnList()
org.apache.derby.iapi.store.access.ScanInfo	getScanInfo()           Return ScanInfo object which describes performance of scan.
RowPosition	getScanPosition()
int	getScanState()
org.apache.derby.iapi.types.DataValueDescriptor[]	getStartKeyValue()
int	getStartSearchOperator()
org.apache.derby.iapi.types.DataValueDescriptor[]	getStopKeyValue()
int	getStopSearchOperator()
void	init(OpenConglomerate open_conglom, org.apache.derby.iapi.services.io.FormatableBitSet scanColumnList, org.apache.derby.iapi.types.DataValueDescriptor[] startKeyValue, int startSearchOperator, org.apache.derby.iapi.store.access.Qualifier[][] qualifier, org.apache.derby.iapi.types.DataValueDescriptor[] stopKeyValue, int stopSearchOperator)           Public Methods of This class:
boolean	isCurrentPositionDeleted()           Returns true if the current position of the scan is at a deleted row.
protected  void	positionAtDoneScan(RowPosition pos)           Do any necessary work to complete the scan.
protected  void	positionAtInitScan(org.apache.derby.iapi.types.DataValueDescriptor[] startKeyValue, int startSearchOperator, org.apache.derby.iapi.store.access.Qualifier[][] qualifier, org.apache.derby.iapi.types.DataValueDescriptor[] stopKeyValue, int stopSearchOperator, RowPosition pos)           Move scan to the the SCAN_INIT state.
protected  void	positionAtNextPage(RowPosition pos)           Position scan to slot before first slot on next 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.
void	reopenScan(org.apache.derby.iapi.types.DataValueDescriptor[] startKeyValue, int startSearchOperator, org.apache.derby.iapi.store.access.Qualifier[][] qualifier, org.apache.derby.iapi.types.DataValueDescriptor[] stopKeyValue, int stopSearchOperator)           Reposition the current scan.
protected  void	reopenScanByRecordHandle(org.apache.derby.iapi.store.raw.RecordHandle startRecordHandle, org.apache.derby.iapi.store.access.Qualifier[][] qualifier)           Reposition the current scan.
void	reopenScanByRowLocation(org.apache.derby.iapi.types.RowLocation startRowLocation, org.apache.derby.iapi.store.access.Qualifier[][] qualifier)           Reposition the current scan.
boolean	replace(org.apache.derby.iapi.types.DataValueDescriptor[] row, org.apache.derby.iapi.services.io.FormatableBitSet validColumns)           Replace the (partial) row at the current position of the scan.
private  void	repositionScanForUpateOper()           Private methods of This class:
protected  void	setRowLocationArray(org.apache.derby.iapi.types.RowLocation[] rowloc_array, int index, RowPosition pos)
void	setScanPosition(RowPosition pos)
void	setScanState(int state)

 

Methods inherited from class org.apache.derby.impl.store.access.conglomerate.GenericController

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

 

Methods inherited from class java.lang.Object

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

 

Methods inherited from interface org.apache.derby.iapi.store.access.conglomerate.ScanManager

savePosition

 

Methods inherited from interface org.apache.derby.iapi.store.access.ScanController

fetchNext, next

 

Methods inherited from interface org.apache.derby.iapi.store.access.GenericScanController

isKeyed, isTableLocked, newRowLocationTemplate

 

Methods inherited from interface org.apache.derby.iapi.store.access.RowCountable

getEstimatedRowCount, setEstimatedRowCount

 

Methods inherited from interface org.apache.derby.iapi.store.access.GroupFetchScanController

fetchNextGroup, fetchNextGroup, next

 

Field Detail

SCAN_INIT

public static final int SCAN_INIT

Constants of the class

See Also:

Constant Field Values

---

SCAN_INPROGRESS

public static final int SCAN_INPROGRESS

See Also:

Constant Field Values

---

SCAN_DONE

public static final int SCAN_DONE

See Also:

Constant Field Values

---

SCAN_HOLD_INIT

public static final int SCAN_HOLD_INIT

See Also:

Constant Field Values

---

SCAN_HOLD_INPROGRESS

public static final int SCAN_HOLD_INPROGRESS

See Also:

Constant Field Values

---

init_scanColumnList

private org.apache.derby.iapi.services.io.FormatableBitSet init_scanColumnList

The following group of fields are all basic input parameters which are provided by the calling code when doing a scan. These are just saved values from what was initially input.

---

init_startKeyValue

private org.apache.derby.iapi.types.DataValueDescriptor[] init_startKeyValue

---

init_startSearchOperator

private int init_startSearchOperator

---

init_qualifier

private org.apache.derby.iapi.store.access.Qualifier[][] init_qualifier

---

init_stopKeyValue

private org.apache.derby.iapi.types.DataValueDescriptor[] init_stopKeyValue

---

init_stopSearchOperator

private int init_stopSearchOperator

---

init_fetchDesc

private org.apache.derby.iapi.store.raw.FetchDescriptor init_fetchDesc

---

scan_state

private int scan_state

Delay positioning the table at the start position until the first next() call.

---

scan_position

protected RowPosition scan_position

The position for the current scan. The can be maintained in any of the following ways: record handle - scan_position.current_rh: The scan maintains it's position using the record handle while it does not have a latch on the page, which is the case anytime control leaves access. The access method must take appropriate steps to make sure the record handle will still be valid when the scan needs to reposition using the record handle. slot number - scan_position.current_slot: While the scan has a latch on the page the scan is positioned using the slot number as the order of the rows cannot change while the latch is held (unless the holder of the latch causes them to move). page number - (RESOLVE - TODO) Sometimes it would be interesting to position a scan "between" pages, such that the next time the scan starts is starts at the next page. This would allow us to efficiently do group scans returning page at atime results. NOT IMPLEMENTED CURRENTLY.

---

stat_numpages_visited

protected int stat_numpages_visited

Performance counters ...

---

stat_numrows_visited

protected int stat_numrows_visited

---

stat_numrows_qualified

protected int stat_numrows_qualified

Constructor Detail

GenericScanController

public GenericScanController()

Method Detail

repositionScanForUpateOper

private final void repositionScanForUpateOper()
                                       throws org.apache.derby.iapi.error.StandardException

Private methods of This class:

---

positionAtInitScan

protected void positionAtInitScan(org.apache.derby.iapi.types.DataValueDescriptor[] startKeyValue,
                                  int startSearchOperator,
                                  org.apache.derby.iapi.store.access.Qualifier[][] qualifier,
                                  org.apache.derby.iapi.types.DataValueDescriptor[] stopKeyValue,
                                  int stopSearchOperator,
                                  RowPosition pos)
                           throws org.apache.derby.iapi.error.StandardException

Move scan to the the SCAN_INIT state.

This routine is called to move the scan to the SCAN_INIT state. It is used both for initialization of the ScanController and by reopenScan().

---

positionAtResumeScan

protected void positionAtResumeScan(RowPosition pos)
                             throws org.apache.derby.iapi.error.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.

---

positionAtStartForForwardScan

protected void positionAtStartForForwardScan(RowPosition pos)
                                      throws org.apache.derby.iapi.error.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.

---

positionAtNextPage

protected void positionAtNextPage(RowPosition pos)
                           throws org.apache.derby.iapi.error.StandardException

Position scan to slot before first slot on next page.

---

positionAtDoneScan

protected void positionAtDoneScan(RowPosition pos)
                           throws org.apache.derby.iapi.error.StandardException

Do any necessary work to complete the scan.

---

reopenScanByRowLocation

public void reopenScanByRowLocation(org.apache.derby.iapi.types.RowLocation startRowLocation,
                                    org.apache.derby.iapi.store.access.Qualifier[][] qualifier)
                             throws org.apache.derby.iapi.error.StandardException

Description copied from interface: org.apache.derby.iapi.store.access.GenericScanController

Reposition the current scan. This call is semantically the same as if the current scan had been closed and a openScan() had been called instead. The scan is reopened against the same conglomerate, and the scan is reopened with the same "scan column list", "hold" and "forUpdate" parameters passed in the original openScan.

The statistics gathered by the scan are not reset to 0 by a reopenScan(), rather they continue to accumulate.

Note that this operation is currently only supported on Heap conglomerates. Also note that order of rows within are heap are not guaranteed, so for instance positioning at a RowLocation in the "middle" of a heap, then inserting more data, then continuing the scan is not guaranteed to see the new rows - they may be put in the "beginning" of the heap.

Specified by:

reopenScanByRowLocation in interface org.apache.derby.iapi.store.access.GenericScanController

---

allocateScanPosition

protected RowPosition allocateScanPosition()
                                    throws org.apache.derby.iapi.error.StandardException

Create object which represents the scan position.

Designed so that extending classes can override and allocate implementation specific row position's.

---

fetchRows

protected int fetchRows(org.apache.derby.iapi.types.DataValueDescriptor[][] row_array,
                        org.apache.derby.iapi.types.RowLocation[] rowloc_array,
                        org.apache.derby.iapi.store.access.BackingStoreHashtable hash_table,
                        long max_rowcnt,
                        int[] key_column_numbers)
                 throws org.apache.derby.iapi.error.StandardException

Fetch the next N rows from the table.

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

---

reopenScanByRecordHandle

protected void reopenScanByRecordHandle(org.apache.derby.iapi.store.raw.RecordHandle startRecordHandle,
                                        org.apache.derby.iapi.store.access.Qualifier[][] qualifier)
                                 throws org.apache.derby.iapi.error.StandardException

Reposition the current scan. This call is semantically the same as if the current scan had been closed and a openScan() had been called instead. The scan is reopened against the same conglomerate, and the scan is reopened with the same "scan column list", "hold" and "forUpdate" parameters passed in the original openScan.

The statistics gathered by the scan are not reset to 0 by a reopenScan(), rather they continue to accumulate.

Note that this operation is currently only supported on Heap conglomerates. Also note that order of rows within are heap are not guaranteed, so for instance positioning at a RowLocation in the "middle" of a heap, then inserting more data, then continuing the scan is not guaranteed to see the new rows - they may be put in the "beginning" of the heap.

---

setRowLocationArray

protected void setRowLocationArray(org.apache.derby.iapi.types.RowLocation[] rowloc_array,
                                   int index,
                                   RowPosition pos)
                            throws org.apache.derby.iapi.error.StandardException

---

init

public void init(OpenConglomerate open_conglom,
                 org.apache.derby.iapi.services.io.FormatableBitSet scanColumnList,
                 org.apache.derby.iapi.types.DataValueDescriptor[] startKeyValue,
                 int startSearchOperator,
                 org.apache.derby.iapi.store.access.Qualifier[][] qualifier,
                 org.apache.derby.iapi.types.DataValueDescriptor[] stopKeyValue,
                 int stopSearchOperator)
          throws org.apache.derby.iapi.error.StandardException

Public Methods of This class:

---

getNumPagesVisited

public final int getNumPagesVisited()

---

getNumRowsVisited

public final int getNumRowsVisited()

---

getNumRowsQualified

public final int getNumRowsQualified()

---

getScanColumnList

public final org.apache.derby.iapi.services.io.FormatableBitSet getScanColumnList()

---

getStartKeyValue

public final org.apache.derby.iapi.types.DataValueDescriptor[] getStartKeyValue()

---

getStartSearchOperator

public final int getStartSearchOperator()

---

getStopKeyValue

public final org.apache.derby.iapi.types.DataValueDescriptor[] getStopKeyValue()

---

getStopSearchOperator

public final int getStopSearchOperator()

---

getQualifier

public final org.apache.derby.iapi.store.access.Qualifier[][] getQualifier()

---

getScanState

public final int getScanState()

---

setScanState

public final void setScanState(int state)

---

getScanPosition

public final RowPosition getScanPosition()

---

setScanPosition

public final void setScanPosition(RowPosition pos)

---

closeScan

private void closeScan()
                throws org.apache.derby.iapi.error.StandardException

Public Methods implementing ScanController:

---

close

public void close()
           throws org.apache.derby.iapi.error.StandardException

Description copied from interface: org.apache.derby.iapi.store.access.GenericScanController

Close the scan. This method always succeeds, and never throws any exceptions. Callers must not use the scan controller after closing it; they are strongly advised to clear out the scan controller reference after closing.

Specified by:

close in interface org.apache.derby.iapi.store.access.GenericScanController

Overrides:

close in class GenericController

---

closeForEndTransaction

public boolean closeForEndTransaction(boolean closeHeldScan)
                               throws org.apache.derby.iapi.error.StandardException

Description copied from interface: org.apache.derby.iapi.store.access.conglomerate.ScanManager

Close scan as part of terminating a transaction.

Use this call to close the scan resources as part of committing or aborting a transaction. The normal close() routine may do some cleanup that is either unnecessary, or not correct due to the unknown condition of the scan following a transaction ending error. Use this call when closing all scans as part of an abort of a transaction.

Specified by:

closeForEndTransaction in interface org.apache.derby.iapi.store.access.conglomerate.ScanManager

---

delete

public boolean delete()
               throws org.apache.derby.iapi.error.StandardException

Description copied from interface: org.apache.derby.iapi.store.access.ScanController

Delete the row at the current position of the scan.

Specified by:

delete in interface org.apache.derby.iapi.store.access.ScanController

---

didNotQualify

public void didNotQualify()
                   throws org.apache.derby.iapi.error.StandardException

A call to allow client to indicate that current row does not qualify.

Indicates to the ScanController that the current row does not qualify for the scan. If the isolation level of the scan allows, this may result in the scan releasing the lock on this row.

Note that some scan implimentations may not support releasing locks on non-qualifying rows, or may delay releasing the lock until sometime later in the scan (ie. it may be necessary to keep the lock until either the scan is repositioned on the next row or page).

This call should only be made while the scan is positioned on a current valid row. RESOLVE (mikem-05/29/98) - Implement this when we support levels of concurrency less than serializable.

Specified by:

didNotQualify in interface org.apache.derby.iapi.store.access.ScanController

---

fetchSet

public void fetchSet(long max_rowcnt,
                     int[] key_column_numbers,
                     org.apache.derby.iapi.store.access.BackingStoreHashtable hash_table)
              throws org.apache.derby.iapi.error.StandardException

Insert all rows that qualify for the current scan into the input Hash table.

This routine scans executes the entire scan as described in the openScan call. For every qualifying unique row value an entry is placed into the HashTable. For unique row values the entry in the Hashtable has a key value of the object stored in row[key_column_number], and the value of the data is row. For row values with duplicates, the key value is also row[key_column_number], but the value of the data is a Vector of rows. The caller will have to call "instanceof" on the data value object if duplicates are expected, to determine if the data value of the Hashtable entry is a row or is a Vector of rows.

Note, that for this routine to work efficiently the caller must ensure that the object in row[key_column_number] implements the hashCode and equals method as appropriate for it's datatype.

It is expected that this call will be the first and only call made in an openscan. Qualifiers and stop position of the openscan are applied just as in a normal scan. This call is logically equivalent to the caller performing the following: import java.util.Hashtable; hash_table = new Hashtable(); while (next()) { row = create_new_row(); fetch(row); if ((duplicate_value = hash_table.put(row[key_column_number], row)) != null) { Vector row_vec; // inserted a duplicate if ((duplicate_value instanceof vector)) { row_vec = (Vector) duplicate_value; } else { // allocate vector to hold duplicates row_vec = new Vector(2); // insert original row into vector row_vec.addElement(duplicate_value); // put the vector as the data rather than the row hash_table.put(row[key_column_number], row_vec); } // insert new row into vector row_vec.addElement(row); } }

The columns of the row will be the standard columns returned as part of a scan, as described by the validColumns - see openScan for description. RESOLVE - is this ok? or should I hard code somehow the row to be the first column and the row location?

Currently it is only possible to hash on the first column in the conglomerate, in the future we may change the interface to allow hashing either on a different column or maybe on a combination of columns.

No overflow to external storage is provided, so calling this routine on a 1 gigabyte conglomerate will incur at least 1 gigabyte of memory (probably failing with a java out of memory condition). If this routine gets an out of memory condition, or if "max_rowcnt" is exceeded then then the routine will give up, empty the Hashtable, and return "false."

On exit from this routine, whether the fetchSet() succeeded or not the scan is complete, it is positioned just the same as if the scan had been drained by calling "next()" until it returns false (ie. fetchNext() and next() calls will return false). reopenScan() can be called to restart the scan.

RESOLVE - until we get row counts what should we do for sizing the the size, capasity, and load factor of the hash table. For now it is up to the caller to create the Hashtable, Access does not reset any parameters.

RESOLVE - I am not sure if access should be in charge of allocating the new row objects. I know that I can do this in the case of btree's, but I don't think I can do this in heaps. Maybe this is solved by work to be done on the sort interface.

Specified by:

fetchSet in interface org.apache.derby.iapi.store.access.conglomerate.ScanManager

---

reopenScan

public void reopenScan(org.apache.derby.iapi.types.DataValueDescriptor[] startKeyValue,
                       int startSearchOperator,
                       org.apache.derby.iapi.store.access.Qualifier[][] qualifier,
                       org.apache.derby.iapi.types.DataValueDescriptor[] stopKeyValue,
                       int stopSearchOperator)
                throws org.apache.derby.iapi.error.StandardException

Reposition the current scan. This call is semantically the same as if the current scan had been closed and a openScan() had been called instead. The scan is reopened with against the same conglomerate, and the scan is reopened with the same "hold" and "forUpdate" parameters passed in the original openScan. The previous template row continues to be used.

Specified by:

reopenScan in interface org.apache.derby.iapi.store.access.GenericScanController

---

replace

public boolean replace(org.apache.derby.iapi.types.DataValueDescriptor[] row,
                       org.apache.derby.iapi.services.io.FormatableBitSet validColumns)
                throws org.apache.derby.iapi.error.StandardException

Description copied from interface: org.apache.derby.iapi.store.access.ScanController

Replace the (partial) row at the current position of the scan.

Specified by:

replace in interface org.apache.derby.iapi.store.access.ScanController

---

doesCurrentPositionQualify

public boolean doesCurrentPositionQualify()
                                   throws org.apache.derby.iapi.error.StandardException

Returns true if the current position of the scan still qualifies under the set of qualifiers passed to the openScan(). When called this routine will reapply all qualifiers against the row currently positioned and return true if the row still qualifies. If the row has been deleted or no longer passes the qualifiers then this routine will return false. This case can come about if the current scan or another scan on the same table in the same transaction deleted the row or changed columns referenced by the qualifier after the next() call which positioned the scan at this row. Note that for comglomerates which don't support update, like btree's, there is no need to recheck the qualifiers. The results of a fetch() performed on a scan positioned on a deleted row are undefined.

Specified by:

doesCurrentPositionQualify in interface org.apache.derby.iapi.store.access.ScanController

---

fetch

public void fetch(org.apache.derby.iapi.types.DataValueDescriptor[] row)
           throws org.apache.derby.iapi.error.StandardException

Description copied from interface: org.apache.derby.iapi.store.access.ScanController

Fetch the (partial) row at the current position of the Scan. The value in the destRow storable row is replaced with the value of the row at the current scan position. The columns of the destRow row must be of the same type as the actual columns in the underlying conglomerate. The number of elements in fetch must be compatible with the number of scan columns requested at the openScan call time.
A fetch can return a sub-set of the scan columns reqested at scan open time by supplying a destRow will less elements than the number of requested columns. In this case the N leftmost of the requested columns are fetched, where N = destRow.length. In the case where all columns are rested and N = 2 then columns 0 and 1 are returned. In the case where the openScan FormatableBitSet requested columns 1, 4 and 7, then columns 1 and 4 would be fetched when N = 2.
The results of a fetch() performed on a scan after next() has returned false are undefined. A fetch() performed on a scan positioned on a deleted row will throw a StandardException with state = SQLState.AM_RECORD_NOT_FOUND. Note that this can happen even if next() has returned true (for instance the client can delete the row, or if using read uncommitted another thread can delete the row after the next() call but before the fetch).

Specified by:

fetch in interface org.apache.derby.iapi.store.access.ScanController

---

fetchLocation

public void fetchLocation(org.apache.derby.iapi.types.RowLocation templateLocation)
                   throws org.apache.derby.iapi.error.StandardException

Fetch the location of the current position in the scan.

Specified by:

fetchLocation in interface org.apache.derby.iapi.store.access.ScanController

---

getScanInfo

public org.apache.derby.iapi.store.access.ScanInfo getScanInfo()
                                                        throws org.apache.derby.iapi.error.StandardException

Return ScanInfo object which describes performance of scan.

Return ScanInfo object which contains information about the current scan.

Specified by:

getScanInfo in interface org.apache.derby.iapi.store.access.GenericScanController

---

isCurrentPositionDeleted

public boolean isCurrentPositionDeleted()
                                 throws org.apache.derby.iapi.error.StandardException

Returns true if the current position of the scan is at a deleted row. This case can come about if the current scan or another scan on the same table in the same transaction deleted the row after the next() call which positioned the scan at this row. The results of a fetch() performed on a scan positioned on a deleted row are undefined.

Specified by:

isCurrentPositionDeleted in interface org.apache.derby.iapi.store.access.ScanController

---

Overview  Package   Class  Use  Deprecated  Index
Home >> All >> org >> apache >> derby >> impl >> store >> access >> [ conglomerate overview ]	PREV CLASS  NEXT CLASS
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD	DETAIL: FIELD | CONSTR | METHOD

---