Class GenericScanController
- All Implemented Interfaces:
ScanManager
,GenericScanController
,GroupFetchScanController
,RowCountable
,ScanController
- Direct Known Subclasses:
HeapScan
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate FetchDescriptor
private Qualifier[][]
private FormatableBitSet
The following group of fields are all basic input parameters which are provided by the calling code when doing a scan.private DataValueDescriptor[]
private int
private DataValueDescriptor[]
private int
private long
This is the sequence number for when a record id can be reused.protected boolean
If this flag is set to true, a RowLocation returned from this controller may have been reused for another row.static final int
static final int
static final int
static final int
Constants of the classstatic final int
protected RowPosition
The position for the current scan.private int
Delay positioning the table at the start position until the first next() call.protected int
Performance counters ...protected int
protected int
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
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Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionprotected RowPosition
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
Public Methods implementing ScanController:boolean
delete()
Delete the row at the current position of the scan.void
A call to allow client to indicate that current row does not qualify.boolean
Returns true if the current position of the scan still qualifies under the set of qualifiers passed to the openScan().void
fetch
(DataValueDescriptor[] row) Fetch the row at the current position of the Scan.private void
fetch
(DataValueDescriptor[] row, boolean qualify) Fetch the row at the current position of the Scan.void
fetchLocation
(RowLocation templateLocation) Fetch the location of the current position in the scan.protected int
fetchRows
(DataValueDescriptor[][] row_array, RowLocation[] rowloc_array, 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, BackingStoreHashtable hash_table) Insert all rows that qualify for the current scan into the input Hash table.void
Fetch the row at the current position of the Scan without applying the qualifiers.final int
final int
final int
final Qualifier[][]
final FormatableBitSet
Return ScanInfo object which describes performance of scan.final RowPosition
final int
final DataValueDescriptor[]
final int
final DataValueDescriptor[]
final int
void
init
(OpenConglomerate open_conglom, FormatableBitSet scanColumnList, DataValueDescriptor[] startKeyValue, int startSearchOperator, Qualifier[][] qualifier, DataValueDescriptor[] stopKeyValue, int stopSearchOperator) Public Methods of This class:boolean
Returns true if the current position of the scan is at a deleted row.boolean
Return true is the scan has been closed after a commit, but was opened with holdability and can be reopened using positionAtRowLocation.protected abstract RowLocation
Make a RowLocation from a RowPositionprotected void
Do any necessary work to complete the scan.protected void
positionAtInitScan
(DataValueDescriptor[] startKeyValue, int startSearchOperator, Qualifier[][] qualifier, DataValueDescriptor[] stopKeyValue, int stopSearchOperator, RowPosition pos) Move scan to the the SCAN_INIT state.protected void
Position scan to slot before first slot on next page.protected void
Reposition the scan upon entering the fetchRows loop.protected void
Move the scan from SCAN_INIT to SCAN_INPROGRESS.protected final boolean
Reopens the scan after it has been closed as part of a commit.void
reopenScan
(DataValueDescriptor[] startKeyValue, int startSearchOperator, Qualifier[][] qualifier, DataValueDescriptor[] stopKeyValue, int stopSearchOperator) Reposition the current scan.protected void
reopenScanByRecordHandle
(RecordHandle startRecordHandle, Qualifier[][] qualifier) Reposition the current scan.void
reopenScanByRowLocation
(RowLocation startRowLocation, Qualifier[][] qualifier) Reposition the current scan.boolean
replace
(DataValueDescriptor[] row, FormatableBitSet validColumns) Replace the (partial) row at the current position of the scan.private final void
Private methods of This class:protected abstract void
setRowLocationArray
(RowLocation[] rowloc_array, int index, RowPosition pos) final void
final 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.GenericScanController
isKeyed, isTableLocked, newRowLocationTemplate
Methods inherited from interface org.apache.derby.iapi.store.access.GroupFetchScanController
fetchNextGroup, fetchNextGroup, next
Methods inherited from interface org.apache.derby.iapi.store.access.RowCountable
getEstimatedRowCount, setEstimatedRowCount
Methods inherited from interface org.apache.derby.iapi.store.access.ScanController
fetchNext, next, positionAtRowLocation
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Field Details
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SCAN_INIT
public static final int SCAN_INITConstants of the class- See Also:
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SCAN_INPROGRESS
public static final int SCAN_INPROGRESS- See Also:
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SCAN_DONE
public static final int SCAN_DONE- See Also:
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SCAN_HOLD_INIT
public static final int SCAN_HOLD_INIT- See Also:
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SCAN_HOLD_INPROGRESS
public static final int SCAN_HOLD_INPROGRESS- See Also:
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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
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init_startSearchOperator
private int init_startSearchOperator -
init_qualifier
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init_stopKeyValue
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init_stopSearchOperator
private int init_stopSearchOperator -
init_fetchDesc
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scan_state
private int scan_stateDelay positioning the table at the start position until the first next() call. -
rowLocationsInvalidated
protected boolean rowLocationsInvalidatedIf this flag is set to true, a RowLocation returned from this controller may have been reused for another row. -
reusableRecordIdSequenceNumber
private long reusableRecordIdSequenceNumberThis is the sequence number for when a record id can be reused. If it has been changed in the container, a RowLocation may be reused for another row. -
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_visitedPerformance counters ... -
stat_numrows_visited
protected int stat_numrows_visited -
stat_numrows_qualified
protected int stat_numrows_qualified
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Constructor Details
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GenericScanController
public GenericScanController()
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Method Details
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repositionScanForUpateOper
Private methods of This class:- Throws:
StandardException
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positionAtInitScan
protected void positionAtInitScan(DataValueDescriptor[] startKeyValue, int startSearchOperator, Qualifier[][] qualifier, DataValueDescriptor[] stopKeyValue, int stopSearchOperator, RowPosition pos) throws 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().
- Throws:
StandardException
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positionAtResumeScan
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.
- Throws:
StandardException
- Standard exception policy.
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positionAtStartForForwardScan
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.
- Throws:
StandardException
- Standard exception policy.
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positionAtNextPage
Position scan to slot before first slot on next page.- Throws:
StandardException
- Standard exception policy.
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positionAtDoneScan
Do any necessary work to complete the scan.- Throws:
StandardException
- Standard exception policy.
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reopenScanByRowLocation
public void reopenScanByRowLocation(RowLocation startRowLocation, Qualifier[][] qualifier) throws StandardException Description copied from interface: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 interfaceGenericScanController
- Parameters:
startRowLocation
- An existing RowLocation within the conglomerate, at which to position the start of the scan. The scan will begin at this location and continue forward until the end of the conglomerate. Positioning at a non-existent RowLocation (ie. an invalid one or one that had been deleted), will result in an exception being thrown when the first next operation is attempted.qualifier
- An array of qualifiers which, applied to each key, restrict the rows returned by the scan. Rows for which any one of the qualifiers returns false are not returned by the scan. If null, all rows are returned.- Throws:
StandardException
- Standard exception policy.
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allocateScanPosition
Create object which represents the scan position.Designed so that extending classes can override and allocate implementation specific row position's.
- Throws:
StandardException
- Standard exception policy.
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fetchRows
protected int fetchRows(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().
- Throws:
StandardException
- Standard exception policy.
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reopenScanByRecordHandle
protected void reopenScanByRecordHandle(RecordHandle startRecordHandle, Qualifier[][] qualifier) throws 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.
- Parameters:
startRecordHandle
- An existing RecordHandle within the conglomerate, at which to position the start of the scan. The scan will begin at this location and continue forward until the end of the conglomerate. Positioning at a non-existent RowLocation (ie. an invalid one or one that had been deleted), will result in an exception being thrown when the first next operation is attempted.qualifier
- An array of qualifiers which, applied to each key, restrict the rows returned by the scan. Rows for which any one of the qualifiers returns false are not returned by the scan. If null, all rows are returned.- Throws:
StandardException
- Standard exception policy.
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setRowLocationArray
protected abstract void setRowLocationArray(RowLocation[] rowloc_array, int index, RowPosition pos) throws StandardException - Throws:
StandardException
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makeRowLocation
Make a RowLocation from a RowPosition- Throws:
StandardException
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init
public void init(OpenConglomerate open_conglom, FormatableBitSet scanColumnList, DataValueDescriptor[] startKeyValue, int startSearchOperator, Qualifier[][] qualifier, DataValueDescriptor[] stopKeyValue, int stopSearchOperator) throws StandardException Public Methods of This class:- Throws:
StandardException
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getNumPagesVisited
public final int getNumPagesVisited() -
getNumRowsVisited
public final int getNumRowsVisited() -
getNumRowsQualified
public final int getNumRowsQualified() -
getScanColumnList
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getStartKeyValue
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getStartSearchOperator
public final int getStartSearchOperator() -
getStopKeyValue
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getStopSearchOperator
public final int getStopSearchOperator() -
getQualifier
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getScanState
public final int getScanState() -
setScanState
public final void setScanState(int state) -
getScanPosition
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setScanPosition
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closeScan
Public Methods implementing ScanController:- Throws:
StandardException
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close
Description copied from interface: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 interfaceGenericScanController
- Overrides:
close
in classGenericController
- Throws:
StandardException
- Standard exception policy.
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reopenAfterEndTransaction
Reopens the scan after it has been closed as part of a commit. This method will check the reusableRecordIdSequenceNumber of the container, and will set the rowLocationsInvalidated flag if it has changed.- Returns:
- true if the conglomerate has been reopened
- Throws:
StandardException
- Derby standard exception
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closeForEndTransaction
Description copied from interface: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 interfaceScanManager
- Parameters:
closeHeldScan
- If true, means to close scan even if it has been opened to be kept opened across commit. This is used to close these scans on abort.- Returns:
- boolean indicating that the close has resulted in a real close of the scan. A held scan will return false if called by closeForEndTransaction(false), otherwise it will return true. A non-held scan will always return true.
- Throws:
StandardException
- Standard exception policy.
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delete
Description copied from interface:ScanController
Delete the row at the current position of the scan.- Specified by:
delete
in interfaceScanController
- Returns:
- true if the delete was successful, false if the current position is no longer valid (ie. if it was already deleted).
- Throws:
StandardException
- Standard exception policy.- See Also:
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didNotQualify
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 interfaceScanController
- Throws:
StandardException
- Standard exception policy.
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fetchSet
public void fetchSet(long max_rowcnt, int[] key_column_numbers, BackingStoreHashtable hash_table) throws 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
List
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 aList
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 interfaceScanManager
- Parameters:
max_rowcnt
- The maximum number of rows to insert into the Hash table. Pass in -1 if there is no maximum.key_column_numbers
- The column numbers of the columns in the scan result row to be the key to the Hashtable. "0" is the first column in the scan result row (which may be different than the first column in the row in the table of the scan).hash_table
- The java HashTable to load into.- Throws:
StandardException
- Standard exception policy.
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reopenScan
public void reopenScan(DataValueDescriptor[] startKeyValue, int startSearchOperator, Qualifier[][] qualifier, DataValueDescriptor[] stopKeyValue, int stopSearchOperator) throws 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 interfaceGenericScanController
- Parameters:
startKeyValue
- An indexable row which holds a (partial) key value which, in combination with the startSearchOperator, defines the starting position of the scan. If null, the starting position of the scan is the first row of the conglomerate.startSearchOperator
- an operator which defines how the startKeyValue is to be searched for. If startSearchOperator is ScanController.GE, the scan starts on the first row which is greater than or equal to the startKeyValue. If startSearchOperation is ScanController.GT, the scan starts on the first row whose key is greater than startKeyValue. The startSearchOperation parameter is ignored if the startKeyValue parameter is null.qualifier
- An array of qualifiers which, applied to each key, restrict the rows returned by the scan. Rows for which any one of the qualifiers returns false are not returned by the scan. If null, all rows are returned.stopKeyValue
- An indexable row which holds a (partial) key value which, in combination with the stopSearchOperator, defines the ending position of the scan. If null, the ending position of the scan is the last row of the conglomerate.stopSearchOperator
- an operator which defines how the stopKeyValue is used to determine the scan stopping position. If stopSearchOperation is ScanController.GE, the scan stops just before the first row which is greater than or equal to the stopKeyValue. If stopSearchOperation is ScanController.GT, the scan stops just before the first row whose key is greater than startKeyValue. The stopSearchOperation parameter is ignored if the stopKeyValue parameter is null.- Throws:
StandardException
- Standard exception policy.
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replace
public boolean replace(DataValueDescriptor[] row, FormatableBitSet validColumns) throws StandardException Description copied from interface:ScanController
Replace the (partial) row at the current position of the scan.- Specified by:
replace
in interfaceScanController
- Returns:
- true if the replace was successful, false if the current position is no longer valid (ie. if it was deleted).
- Throws:
StandardException
- Standard exception policy.- See Also:
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doesCurrentPositionQualify
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 interfaceScanController
- Throws:
StandardException
- Standard exception policy.
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fetchWithoutQualify
Fetch the row at the current position of the Scan without applying the qualifiers.- Specified by:
fetchWithoutQualify
in interfaceScanController
- Parameters:
row
- The row into which the value of the current position in the scan is to be stored.- Throws:
StandardException
- Standard exception policy.- See Also:
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isHeldAfterCommit
Description copied from interface:ScanController
Return true is the scan has been closed after a commit, but was opened with holdability and can be reopened using positionAtRowLocation.- Specified by:
isHeldAfterCommit
in interfaceScanController
- Throws:
StandardException
- Standard exception policy.- See Also:
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fetch
Fetch the row at the current position of the Scan.- Specified by:
fetch
in interfaceScanController
- Parameters:
row
- The row into which the value of the current position in the scan is to be stored.- Throws:
StandardException
- Standard exception policy.- See Also:
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fetch
Fetch the row at the current position of the Scan.- Parameters:
row
- The row into which the value of the current position in the scan is to be stored.qualify
- Indicates whether the qualifiers should be applied.- Throws:
StandardException
- Standard exception policy.
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fetchLocation
Fetch the location of the current position in the scan.- Specified by:
fetchLocation
in interfaceScanController
- Throws:
StandardException
- Standard exception policy.- See Also:
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getScanInfo
Return ScanInfo object which describes performance of scan.Return ScanInfo object which contains information about the current scan.
- Specified by:
getScanInfo
in interfaceGenericScanController
- Returns:
- The ScanInfo object which contains info about current scan.
- Throws:
StandardException
- Standard exception policy.- See Also:
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isCurrentPositionDeleted
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 interfaceScanController
- Throws:
StandardException
- Standard exception policy.
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