org.apache.derby.impl.sql
Class GenericColumnDescriptor

java.lang.Object
  org.apache.derby.impl.sql.GenericColumnDescriptor

All Implemented Interfaces:

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

public final class GenericColumnDescriptor
extends java.lang.Object
implements ResultColumnDescriptor, Formatable

This is a stripped down implementation of a column descriptor that is intended for generic use. It can be seralized and attached to plans.

See Also:

Serialized Form

Field Summary

private int	columnPos
private boolean	hasGenerationClause
private boolean	isAutoincrement
private java.lang.String	name This class implements Formatable.
private java.lang.String	schemaName
private java.lang.String	tableName
private DataTypeDescriptor	type
private boolean	updatableByCursor

Constructor Summary

GenericColumnDescriptor()
Niladic constructor for Formatable

GenericColumnDescriptor(ResultColumnDescriptor rcd)
This constructor is used to build a generic (and formatable) ColumnDescriptor.

GenericColumnDescriptor(java.lang.String name, DataTypeDescriptor type)

Method Summary

int	getColumnPosition() Get the position of the Column.
java.lang.String	getName() Returns the name of the Column.
java.lang.String	getSourceSchemaName() Get the name of the schema for the Column's base table, if any.
java.lang.String	getSourceTableName() Get the name of the underlying(base) table this column comes from, if any.
private DataTypeDescriptor	getStoredDataTypeDescriptor(java.lang.Object o) When retrieving a DataTypeDescriptor, it might just be a regular DataTypeDescriptor or may be an OldRoutineType, as used for Routine parameters and return values prior to DERBY-2775.
DataTypeDescriptor	getType() Returns a DataTypeDescriptor for the column.
int	getTypeFormatId() Get the formatID which corresponds to this class.
boolean	hasGenerationClause() Return true if this result column represents a generated column.
boolean	isAutoincrement() Tell us if the column is an autoincrement column or not.
void	readExternal(java.io.ObjectInput in) Read this object from a stream of stored objects.
java.lang.String	toString()
boolean	updatableByCursor() Return true if the column is wirtable by a positioned update.
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

name

private java.lang.String name

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.

schemaName

private java.lang.String schemaName

tableName

private java.lang.String tableName

columnPos

private int columnPos

type

private DataTypeDescriptor type

isAutoincrement

private boolean isAutoincrement

updatableByCursor

private boolean updatableByCursor

hasGenerationClause

private boolean hasGenerationClause

Constructor Detail

GenericColumnDescriptor

public GenericColumnDescriptor()

Niladic constructor for Formatable

GenericColumnDescriptor

public GenericColumnDescriptor(java.lang.String name,
                               DataTypeDescriptor type)

GenericColumnDescriptor

public GenericColumnDescriptor(ResultColumnDescriptor rcd)

This constructor is used to build a generic (and formatable) ColumnDescriptor. The idea is that it can be passed a ColumnDescriptor from a query tree and convert it to something that can be used anywhere.

Parameters:

rcd - the ResultColumnDescriptor

Method Detail

getType

public DataTypeDescriptor getType()

Returns a DataTypeDescriptor for the column. This DataTypeDescriptor will not represent an actual value, it will only represent the type that all values in the column will have.

Specified by:

getType in interface ResultColumnDescriptor

Returns:

A DataTypeDescriptor describing the type of the column.

getName

public java.lang.String getName()

Returns the name of the Column.

Specified by:

getName in interface ResultColumnDescriptor

Returns:

A String containing the name of the column.

getSourceSchemaName

public java.lang.String getSourceSchemaName()

Get the name of the schema for the Column's base table, if any. Following example queries will all return APP (assuming user is in schema APP) select t.a from t select b.a from t as b select app.t.a from t

Specified by:

getSourceSchemaName in interface ResultColumnDescriptor

Returns:

A String containing the name of the schema of the Column's table. If the column is not in a schema (i.e. is a derived column), it returns NULL.

getSourceTableName

public java.lang.String getSourceTableName()

Get the name of the underlying(base) table this column comes from, if any. Following example queries will all return T select a from t select b.a from t as b select t.a from t

Specified by:

getSourceTableName in interface ResultColumnDescriptor

Returns:

A String containing the name of the Column's base table. If the column is not in a table (i.e. is a derived column), it returns NULL.

getColumnPosition

public int getColumnPosition()

Get the position of the Column. NOTE - position is 1-based.

Specified by:

getColumnPosition in interface ResultColumnDescriptor

Returns:

An int containing the position of the Column within the table.

isAutoincrement

public boolean isAutoincrement()

Description copied from interface: ResultColumnDescriptor

Tell us if the column is an autoincrement column or not.

Specified by:

isAutoincrement in interface ResultColumnDescriptor

Returns:

TRUE, if the column is a base column of a table and is an autoincrement column.

updatableByCursor

public boolean updatableByCursor()

Description copied from interface: ResultColumnDescriptor

Return true if the column is wirtable by a positioned update.

Specified by:

updatableByCursor in interface ResultColumnDescriptor

Returns:

TRUE, if the column is a base column of a table and is writable by a positioned update.

hasGenerationClause

public boolean hasGenerationClause()

Description copied from interface: ResultColumnDescriptor

Return true if this result column represents a generated column.

Specified by:

hasGenerationClause in interface ResultColumnDescriptor

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

getStoredDataTypeDescriptor

private DataTypeDescriptor getStoredDataTypeDescriptor(java.lang.Object o)

When retrieving a DataTypeDescriptor, it might just be a regular DataTypeDescriptor or may be an OldRoutineType, as used for Routine parameters and return values prior to DERBY-2775. If it is not a regular DataTypeDescriptor, it must be an OldRoutineType, so convert it to a DataTypeDescriptor DERBY-4913

Parameters:

o - object as obtained by fh.get("type") in readExternal

Returns:

DataTypeDescriptor