com.metamatrix.query.sql.symbol
Class ScalarSubquery

java.lang.Object
  com.metamatrix.query.sql.symbol.ScalarSubquery

All Implemented Interfaces:

SubqueryContainer, LanguageObject, Expression, ValueIteratorProvider, java.io.Serializable, java.lang.Cloneable

public class ScalarSubquery
extends java.lang.Object
implements Expression, SubqueryContainer, ValueIteratorProvider

This is an Expression implementation that can be used in a SELECT clause. It has a subquery Command which must only produce exactly one value (or an Exception will result during query processing). It's type will be the type of the one symbol to be produced. In theory an instance of this could be used wherever an Expression is legal, but it is specifically needed for the SELECT clause.

See Also:

Serialized Form

Constructor Summary

ScalarSubquery(Command subqueryCommand)

Method Summary

void	acceptVisitor(LanguageVisitor visitor) Method for accepting a visitor.
java.lang.Object	clone() Returns a safe clone
boolean	equals(java.lang.Object obj) Compare this ScalarSubquery to another ScalarSubquery for equality.
Command	getCommand() Returns the subquery Command object
java.lang.Class	getType() Get the return type of this expression.
ValueIterator	getValueIterator() Returns always the same instance of a ValueIterator, but resets it each time this method is called
int	hashCode() Get hashcode for the object
boolean	isResolved() Return true if expression has been fully resolved.
void	setCommand(Command command) Sets the command.
void	setType(java.lang.Class type) Set type of ScalarSubquery
void	setValueIterator(ValueIterator valueIterator) Set the ValueIterator on this object (the ValueIterator will encapsulate the single-column results of the subquery processor plan).
java.lang.String	toString() Returns string representation of this object.

Methods inherited from class java.lang.Object

finalize, getClass, notify, notifyAll, wait, wait, wait

Constructor Detail

ScalarSubquery

public ScalarSubquery(Command subqueryCommand)

Method Detail

getValueIterator

public ValueIterator getValueIterator()

Returns always the same instance of a ValueIterator, but resets it each time this method is called

Specified by:

getValueIterator in interface ValueIteratorProvider

Returns:

this object's ValueIterator instance (always the same instance)

Throws:

MetaMatrixRuntimeException - if the subquery for this set criteria has not yet been processed and no value iterator is available

See Also:

com.metamatrix.query.sql.lang.SubqueryLanguageObject#getValueIterator()

setValueIterator

public void setValueIterator(ValueIterator valueIterator)

Set the ValueIterator on this object (the ValueIterator will encapsulate the single-column results of the subquery processor plan). This ValueIterator must be set before processing (before the Criteria can be evaluated). Also, this ValueIterator should be considered transient - only available during processing - and it will not be cloned should this Criteria object be cloned.

Specified by:

setValueIterator in interface ValueIteratorProvider

Parameters:

valueIterator - encapsulating the results of the sub query

isResolved

public boolean isResolved()

Description copied from interface: Expression

Return true if expression has been fully resolved. Typically the QueryResolver component will handle resolution of an expression.

Specified by:

isResolved in interface Expression

Returns:

True if resolved

See Also:

Expression.isResolved()

getType

public java.lang.Class getType()

Description copied from interface: Expression

Get the return type of this expression. This method will not necessarily work right before resolution (Expression.isResolved() returns true).

Specified by:

getType in interface Expression

Returns:

Java class name

See Also:

Expression.getType()

setType

public void setType(java.lang.Class type)

Set type of ScalarSubquery

Parameters:

type - New type

getCommand

public Command getCommand()

Description copied from interface: SubqueryContainer

Returns the subquery Command object

Specified by:

getCommand in interface SubqueryContainer

Returns:

the subquery Command object

See Also:

com.metamatrix.query.sql.lang.SubqueryLanguageObject#getCommand()

setCommand

public void setCommand(Command command)

Sets the command. Also modifies the hash code of this object, so caution should be used in using this method.

Specified by:

setCommand in interface SubqueryContainer

Parameters:

command - the subquery Command object

See Also:

com.metamatrix.query.sql.lang.SubqueryLanguageObject#setCommand()

acceptVisitor

public void acceptVisitor(LanguageVisitor visitor)

Description copied from interface: LanguageObject

Method for accepting a visitor. It is the responsibility of the language object to call back on the visitor.

Specified by:

acceptVisitor in interface LanguageObject

Parameters:

visitor - Visitor being used

equals

public boolean equals(java.lang.Object obj)

Compare this ScalarSubquery to another ScalarSubquery for equality.

Overrides:

equals in class java.lang.Object

Parameters:

obj - Other object

Returns:

true if objects are equal

hashCode

public int hashCode()

Get hashcode for the object

Overrides:

hashCode in class java.lang.Object

Returns:

Hash code

clone

public java.lang.Object clone()

Returns a safe clone

Specified by:

clone in interface LanguageObject

Overrides:

clone in class java.lang.Object

Returns:

Deep clone of this object

See Also:

Object.clone()

toString

public java.lang.String toString()

Returns string representation of this object.

Overrides:

toString in class java.lang.Object

Returns:

String representing the object