org.apache.derby.impl.sql.execute
Class IndexColumnOrder

java.lang.Object
  org.apache.derby.impl.sql.execute.IndexColumnOrder

All Implemented Interfaces:

java.io.Externalizable, java.io.Serializable, Formatable, TypedFormat, ColumnOrdering

public class IndexColumnOrder
extends java.lang.Object
implements ColumnOrdering, Formatable

Basic implementation of ColumnOrdering. Not sure what to tell callers about 0-based versus 1-based numbering. Assume 0-based for now.

See Also:

Serialized Form

Field Summary

(package private) boolean	ascending
(package private) int	colNum This class implements Formatable.
(package private) boolean	nullsOrderedLow indicate whether NULL values should sort low.

Constructor Summary

IndexColumnOrder()
Niladic constructor for formatable

IndexColumnOrder(int colNum)

IndexColumnOrder(int colNum, boolean ascending)

IndexColumnOrder(int colNum, boolean ascending, boolean nullsLow)
constructor used by the ORDER BY clause.

Method Summary

int	getColumnId()
boolean	getIsAscending()
boolean	getIsNullsOrderedLow() Indicate whether NULL values should be ordered below non-NULL.
int	getTypeFormatId() Get the formatID which corresponds to this class.
void	readExternal(java.io.ObjectInput in) Read this object from a stream of stored objects.
java.lang.String	toString()
void	writeExternal(java.io.ObjectOutput out) Write this object out

Methods inherited from class java.lang.Object

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

Field Detail

colNum

int colNum

This class implements Formatable. That means that it can write itself to and from a formatted stream. If you add more fields to this class, make sure that you also write/read them with the writeExternal()/readExternal() methods. If, inbetween releases, you add more fields to this class, then you should bump the version number emitted by the getTypeFormatId() method.

ascending

boolean ascending

nullsOrderedLow

boolean nullsOrderedLow

indicate whether NULL values should sort low. nullsOrderedLow is usually false, because generally Derby defaults to have NULL values compare higher than non-null values, but if the user specifies an ORDER BY clause with a specification that indicates that NULL values should be ordered lower than non-NULL values, thien nullsOrderedLow is set to true.

Constructor Detail

IndexColumnOrder

public IndexColumnOrder()

Niladic constructor for formatable

IndexColumnOrder

public IndexColumnOrder(int colNum)

IndexColumnOrder

public IndexColumnOrder(int colNum,
                        boolean ascending)

IndexColumnOrder

public IndexColumnOrder(int colNum,
                        boolean ascending,
                        boolean nullsLow)

constructor used by the ORDER BY clause. This version of the constructor is used by the compiler when it processes an ORDER BY clause in a SQL statement. For such statements, the user gets to control whether NULL values are ordered as lower than all non-NULL values, or higher than all non-NULL values.

Parameters:

colNum - number of this column

ascending - whether the ORDER BY is ascendeing or descending

nullsLow - whether nulls should be ordered low

Method Detail

getColumnId

public int getColumnId()

Specified by:

getColumnId in interface ColumnOrdering

getIsAscending

public boolean getIsAscending()

Specified by:

getIsAscending in interface ColumnOrdering

getIsNullsOrderedLow

public boolean getIsNullsOrderedLow()

Indicate whether NULL values should be ordered below non-NULL. This function returns TRUE if the user has specified, via the clause in the ORDER BY clause, that NULL values of this column should sort lower than non-NULL values.

Specified by:

getIsNullsOrderedLow in interface ColumnOrdering

Returns:

whether nulls should sort low

writeExternal

public void writeExternal(java.io.ObjectOutput out)
                   throws java.io.IOException

Write this object out

Specified by:

writeExternal in interface java.io.Externalizable

Parameters:

out - write bytes here

Throws:

java.io.IOException - thrown on error

readExternal

public void readExternal(java.io.ObjectInput in)
                  throws java.io.IOException,
                         java.lang.ClassNotFoundException

Read this object from a stream of stored objects.

Specified by:

readExternal in interface java.io.Externalizable

Parameters:

in - read this.

Throws:

java.io.IOException - thrown on error

java.lang.ClassNotFoundException - thrown on error

getTypeFormatId

public int getTypeFormatId()

Get the formatID which corresponds to this class.

Specified by:

getTypeFormatId in interface TypedFormat

Returns:

the formatID of this class

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object