com.metamatrix.query.sql.symbol
Class AggregateSymbol

java.lang.Object
  com.metamatrix.query.sql.symbol.Symbol
      com.metamatrix.query.sql.symbol.SelectSymbol
          com.metamatrix.query.sql.symbol.SingleElementSymbol
              com.metamatrix.query.sql.symbol.ExpressionSymbol
                  com.metamatrix.query.sql.symbol.AggregateSymbol

All Implemented Interfaces:

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

public class AggregateSymbol
extends ExpressionSymbol

An aggregate symbol represents an aggregate function in the SELECT or HAVING clauses. It extends ExpressionSymbol as they have many things in common. The aggregate symbol is typically something like SUM(stock.quantity * 2). There are five supported aggregate functions: COUNT, SUM, AVG, MIN, and MAX. Aggregate functions contain an expression - this data is managed by the super class, ExpressionSymbol. Aggregate functions may also specify a DISTINCT flag to indicate that duplicates should be ignored. The DISTINCT flag may be set for all five aggregate functions but is ignored for the computation of MIN and MAX. One special use of an aggregate symbol is for the symbol COUNT(*). The * expression is encoded by setting the expression to null. This may ONLY be used with the COUNT function.

The type of an aggregate symbol depends on the function and the type of the underlying expression. The type of a COUNT function is ALWAYS integer. MIN and MAX functions take the type of their contained expression. AVG and SUM vary depending on the type of the expression. If the expression is of a type other than biginteger, the aggregate function returns type long. For the case of biginteger, the aggregate function returns type biginteger. Similarly, all floating point expressions not of type bigdecimal return type double and bigdecimal maps to bigdecimal.

See Also:

Serialized Form

Field Summary

Fields inherited from class com.metamatrix.query.sql.symbol.SingleElementSymbol

SEPARATOR

Constructor Summary

	AggregateSymbol(java.lang.String name, java.lang.String aggregateFunction, boolean isDistinct, Expression expression) Construct an aggregate symbol with all given data.
protected	AggregateSymbol(java.lang.String name, java.lang.String canonicalName, java.lang.String aggregateFunction, boolean isDistinct, Expression expression) Constructor used for cloning

Method Summary

void	acceptVisitor(LanguageVisitor visitor) Method for accepting a visitor.
java.lang.Object	clone() Return a deep copy of this object
boolean	equals(java.lang.Object obj) ExpressionSymbol matching is not based upon the name
java.lang.String	getAggregateFunction() Get the aggregate function type - this will map to one of the reserved words for the aggregate functions.
java.lang.Class	getType() Get the type of the symbol, which depends on the aggregate function and the type of the contained expression
int	hashCode() Return a hash code for this symbol.
boolean	isDistinct() Get the distinct flag.

Methods inherited from class com.metamatrix.query.sql.symbol.ExpressionSymbol

getExpression, isDerivedExpression, isResolved, setDerivedExpression, setExpression

Methods inherited from class com.metamatrix.query.sql.symbol.SingleElementSymbol

getShortCanonicalName, getShortName, getShortName

Methods inherited from class com.metamatrix.query.sql.symbol.Symbol

getCanonical, getCanonicalName, getName, getOutputName, setName, setOutputName, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

AggregateSymbol

protected AggregateSymbol(java.lang.String name,
                          java.lang.String canonicalName,
                          java.lang.String aggregateFunction,
                          boolean isDistinct,
                          Expression expression)

Constructor used for cloning

Parameters:

name -

canonicalName -

Since:

4.3

AggregateSymbol

public AggregateSymbol(java.lang.String name,
                       java.lang.String aggregateFunction,
                       boolean isDistinct,
                       Expression expression)

Construct an aggregate symbol with all given data.

Parameters:

name - Name of the function

aggregateFunction - Aggregate function type (ReservedWords.COUNT, etc)

isDistinct - True if DISTINCT flag is set

expression - Contained expression

Method Detail

getAggregateFunction

public java.lang.String getAggregateFunction()

Get the aggregate function type - this will map to one of the reserved words for the aggregate functions.

Returns:

Aggregate function type

See Also:

ReservedWords.COUNT, ReservedWords.SUM, ReservedWords.AVG, ReservedWords.MIN, ReservedWords.MAX

isDistinct

public boolean isDistinct()

Get the distinct flag. If true, aggregate symbol will remove duplicates during computation.

Returns:

True if duplicates should be removed during computation

getType

public java.lang.Class getType()

Get the type of the symbol, which depends on the aggregate function and the type of the contained expression

Specified by:

getType in interface Expression

Overrides:

getType in class ExpressionSymbol

Returns:

Type of the symbol

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

Overrides:

acceptVisitor in class ExpressionSymbol

Parameters:

visitor - Visitor being used

clone

public java.lang.Object clone()

Return a deep copy of this object

Specified by:

clone in interface LanguageObject

Overrides:

clone in class ExpressionSymbol

Returns:

Deep copy of this object

hashCode

public int hashCode()

Description copied from class: Symbol

Return a hash code for this symbol.

Overrides:

hashCode in class ExpressionSymbol

Returns:

Hash code

See Also:

ExpressionSymbol.hashCode()

equals

public boolean equals(java.lang.Object obj)

Description copied from class: ExpressionSymbol

ExpressionSymbol matching is not based upon the name

Overrides:

equals in class ExpressionSymbol

Parameters:

obj - Other object

Returns:

True if other obj is a Symbol (or subclass) and name is equal

See Also:

ExpressionSymbol.equals(java.lang.Object)