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A scan is the mechanism for iterating over the rows in a conglomerate, the scan controller is the interface through which access clients control the underlying scan. An instance of a scan controller can be thought of as an open scan.
Scans are opened from a TransactionController.
A ScanController can handle partial rows. Partial rows
are described in RowUtil.
A scan controller is opened with a FormatableBitSet that describes the
columns that need to be returned on a fetch call. This FormatableBitSet
need not include any columns referenced in the qualifers, start
and/or stop keys.
TransactionController.openScan(long, boolean, int, int, int, org.apache.derby.iapi.services.io.FormatableBitSet, org.apache.derby.iapi.types.DataValueDescriptor[], int, org.apache.derby.iapi.store.access.Qualifier[][], org.apache.derby.iapi.types.DataValueDescriptor[], int)
,
GenericScanController
,
RowCountable
,
RowUtil
Field Summary | |
static int |
GE
GE is used to position a scan at values greater than or or equal to the given key in the scan. |
static int |
GT
GT is used to position a scan at values greater than the given key. |
static int |
NA
NA - argument is unused in call. |
Method Summary | |
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(DataValueDescriptor[] destRow)
Fetch the (partial) row at the current position of the Scan. |
void |
fetchLocation(RowLocation destRowLocation)
Fetch the location of the current position in the scan. |
boolean |
fetchNext(DataValueDescriptor[] destRow)
Fetch the (partial) row at the next position of the Scan. |
boolean |
isCurrentPositionDeleted()
Returns true if the current position of the scan is at a deleted row. |
boolean |
next()
Move to the next position in the scan. |
boolean |
replace(DataValueDescriptor[] row,
FormatableBitSet validColumns)
Replace the (partial) row at the current position of the scan. |
Methods inherited from interface org.apache.derby.iapi.store.access.GenericScanController |
close, getScanInfo, isKeyed, isTableLocked, newRowLocationTemplate, reopenScan, reopenScanByRowLocation |
Methods inherited from interface org.apache.derby.iapi.store.access.RowCountable |
getEstimatedRowCount, setEstimatedRowCount |
Field Detail |
public static final int GE
TransactionController.openScan(long, boolean, int, int, int, org.apache.derby.iapi.services.io.FormatableBitSet, org.apache.derby.iapi.types.DataValueDescriptor[], int, org.apache.derby.iapi.store.access.Qualifier[][], org.apache.derby.iapi.types.DataValueDescriptor[], int)
,
Constant Field Valuespublic static final int GT
TransactionController.openScan(long, boolean, int, int, int, org.apache.derby.iapi.services.io.FormatableBitSet, org.apache.derby.iapi.types.DataValueDescriptor[], int, org.apache.derby.iapi.store.access.Qualifier[][], org.apache.derby.iapi.types.DataValueDescriptor[], int)
,
Constant Field Valuespublic static final int NA
TransactionController.openScan(long, boolean, int, int, int, org.apache.derby.iapi.services.io.FormatableBitSet, org.apache.derby.iapi.types.DataValueDescriptor[], int, org.apache.derby.iapi.store.access.Qualifier[][], org.apache.derby.iapi.types.DataValueDescriptor[], int)
,
Constant Field ValuesMethod Detail |
public boolean delete() throws StandardException
StandardException
- Standard exception policy.public void didNotQualify() throws StandardException
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.
StandardException
- Standard exception policy.public boolean doesCurrentPositionQualify() throws StandardException
StandardException
- Standard exception policy.public void fetch(DataValueDescriptor[] destRow) throws StandardException
destRow
- The row into which the value of the current
position in the scan is to be stored.
StandardException
- Standard exception policy.RowUtil
public boolean fetchNext(DataValueDescriptor[] destRow) throws StandardException
destRow
- The destRow row into which the value
of the next position in the scan is to be stored.
StandardException
- Standard exception policy.fetch(org.apache.derby.iapi.types.DataValueDescriptor[])
,
RowUtil
public void fetchLocation(RowLocation destRowLocation) throws StandardException
StandardException
- Standard exception policy.public boolean isCurrentPositionDeleted() throws StandardException
StandardException
- Standard exception policy.public boolean next() throws StandardException
StandardException
- Standard exception policy.public boolean replace(DataValueDescriptor[] row, FormatableBitSet validColumns) throws StandardException
StandardException
- Standard exception policy.RowUtil
|
Built on Tue 2006-10-10 19:23:47+0200, from revision exported | |||||||||
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