Class GenericScanQualifier

java.lang.Object

org.apache.derby.impl.sql.execute.GenericScanQualifier

All Implemented Interfaces:

ScanQualifier, Qualifier

public class GenericScanQualifier
extends Object
implements ScanQualifier

This is the implementation for ScanQualifier. It is used for system and user scans.

Version:

0.1

Field Summary

Fields

Modifier and Type	Field	Description
private int	columnId
private boolean	negateCR
private int	operator
private DataValueDescriptor	orderable
private boolean	orderedNulls
private boolean	properInit
private boolean	unknownRV

Fields inherited from interface Qualifier

CONSTANT, QUERY_INVARIANT, SCAN_INVARIANT, VARIANT

Constructor Summary

Constructors

Constructor	Description
GenericScanQualifier()

Method Summary

Modifier and Type	Method	Description
void	clearOrderableCache()	Clear the DataValueDescriptor cache, if one exists.
int	getColumnId()	Get the (zero based) id of the column to be qualified.
int	getOperator()	Get the operator to use in the comparison.
DataValueDescriptor	getOrderable()	Get the value that the column is to be compared to.
boolean	getOrderedNulls()	Get the getOrderedNulls argument to use in the comparison.
boolean	getUnknownRV()	Get the getOrderedNulls argument to use in the comparison.
boolean	negateCompareResult()	Should the result from the compare operation be negated?
void	reinitialize()	This method reinitializes all the state of the Qualifier.
void	setQualifier(int columnId, DataValueDescriptor orderable, int operator, boolean negateCR, boolean orderedNulls, boolean unknownRV)	Set the info in a ScanQualifier

Methods inherited from class Object

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

Field Details

columnId

private int columnId

orderable

private DataValueDescriptor orderable

operator

private int operator

negateCR

private boolean negateCR

orderedNulls

private boolean orderedNulls

unknownRV

private boolean unknownRV

properInit

private boolean properInit

Constructor Details

GenericScanQualifier

public GenericScanQualifier()

Method Details

getColumnId

public int getColumnId()

Description copied from interface: Qualifier

Get the (zero based) id of the column to be qualified.

This id is the column number of the column in the table, no matter whether a partial column set is being retrieved by the actual fetch. Note that the column being specified in the qualifier must appear in the column list being fetched.

Specified by:

getColumnId in interface Qualifier

See Also:

• Qualifier.getColumnId()

getOrderable

public DataValueDescriptor getOrderable()

Description copied from interface: Qualifier

Get the value that the column is to be compared to.

Specified by:

getOrderable in interface Qualifier

See Also:

• Qualifier.getOrderable()

getOperator

public int getOperator()

Get the operator to use in the comparison.

Specified by:

getOperator in interface Qualifier

See Also:

• Qualifier.getOperator()

negateCompareResult

public boolean negateCompareResult()

Should the result from the compare operation be negated? If true then only rows which fail the compare operation will qualify.

Specified by:

negateCompareResult in interface Qualifier

See Also:

• Qualifier.negateCompareResult()

getOrderedNulls

public boolean getOrderedNulls()

Get the getOrderedNulls argument to use in the comparison.

Specified by:

getOrderedNulls in interface Qualifier

See Also:

• Qualifier.getOrderedNulls()

getUnknownRV

public boolean getUnknownRV()

Get the getOrderedNulls argument to use in the comparison.

Specified by:

getUnknownRV in interface Qualifier

See Also:

• Qualifier.getUnknownRV()

clearOrderableCache

public void clearOrderableCache()

Clear the DataValueDescriptor cache, if one exists. (The DataValueDescriptor can be 1 of 3 types: o VARIANT - cannot be cached as its value can vary within a scan o SCAN_INVARIANT - can be cached within a scan as its value will not change within a scan o QUERY_INVARIANT- can be cached across the life of the query as its value will never change o CONSTANT - immutable

Specified by:

clearOrderableCache in interface Qualifier

See Also:

• Qualifier.getUnknownRV()

reinitialize

public void reinitialize()

This method reinitializes all the state of the Qualifier. It is used to distinguish between resetting something that is query invariant and something that is constant over every execution of a query. Basically, clearOrderableCache() will only clear out its cache if it is a VARIANT or SCAN_INVARIANT value. However, each time a query is executed, the QUERY_INVARIANT qualifiers need to be reset.

Specified by:

reinitialize in interface Qualifier

setQualifier

public void setQualifier(int columnId,
 DataValueDescriptor orderable,
 int operator,
 boolean negateCR,
 boolean orderedNulls,
 boolean unknownRV)

Description copied from interface: ScanQualifier

Set the info in a ScanQualifier

Specified by:

setQualifier in interface ScanQualifier

See Also:

• ScanQualifier.setQualifier(int, DataValueDescriptor, int, boolean, boolean, boolean)