Package com.mckoi.database

Class AbstractFunction

java.lang.Object

com.mckoi.database.AbstractFunction

All Implemented Interfaces:

Function

Direct Known Subclasses:

AbstractAggregateFunction

public abstract class AbstractFunction
extends java.lang.Object
implements Function

An abstract implementation of Function.

Author:

Tobias Downer

Constructor Summary

Constructors

Constructor	Description
AbstractFunction(java.lang.String name, Expression[] params)	Constructs the Function with the given expression array as parameters.

Method Summary

Modifier and Type	Method	Description
java.util.List	allElements()	Returns the list of all elements that are used by this function.
java.util.List	allVariables()	Returns the list of all Variable's that are used by this function.
java.lang.String	getName()	Returns the name of the function.
Expression	getParameter(int n)	Returns the parameter at the given index in the parameters list.
void	init(VariableResolver resolver)	The init function.
boolean	isAggregate(QueryContext context)	Returns whether the function is an aggregate function or not.
boolean	isGlob()	Returns true if the param is the special case glob parameter (*).
int	parameterCount()	Returns the number of parameters for this function.
void	prepareParameters(ExpressionPreparer preparer)	Prepares the parameters of the function.
TType	returnTType()
TType	returnTType(VariableResolver resolver, QueryContext context)	By Default, we assume a function returns a Numeric object.
protected void	setAggregate(boolean status)	Call this from the constructor if the function is an aggregate.
java.lang.String	toString()

Methods inherited from interface com.mckoi.database.Function

evaluate

Methods inherited from class java.lang.Object

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

Constructor Detail

AbstractFunction

public AbstractFunction(java.lang.String name,
                        Expression[] params)

Constructs the Function with the given expression array as parameters.

Method Detail

setAggregate

protected void setAggregate(boolean status)

Call this from the constructor if the function is an aggregate.

parameterCount

public int parameterCount()

Returns the number of parameters for this function.

getParameter

public Expression getParameter(int n)

Returns the parameter at the given index in the parameters list.

isGlob

public boolean isGlob()

Returns true if the param is the special case glob parameter (*).

getName

public java.lang.String getName()

Returns the name of the function. The name is a unique identifier that can be used to recreate this function. This identifier can be used to easily serialize the function when grouped with its parameters.

Specified by:

getName in interface Function

allVariables

public java.util.List allVariables()

Returns the list of all Variable's that are used by this function. This looks up each expression in the list of parameters. This will cascade if the expressions have a Function, etc.

Specified by:

allVariables in interface Function

allElements

public java.util.List allElements()

Returns the list of all elements that are used by this function. This looks up each expression in the list of parameters. This will cascade if the expressions have a Function, etc.

Specified by:

allElements in interface Function

isAggregate

public final boolean isAggregate(QueryContext context)

Returns whether the function is an aggregate function or not.

Specified by:

isAggregate in interface Function

prepareParameters

public void prepareParameters(ExpressionPreparer preparer)
                       throws DatabaseException

Prepares the parameters of the function.

Specified by:

prepareParameters in interface Function

Throws:

DatabaseException

init

public void init(VariableResolver resolver)

The init function. By default, we don't do anything however this should be overwritten if we need to check the parameter arguments.

returnTType

public TType returnTType(VariableResolver resolver,
                         QueryContext context)

By Default, we assume a function returns a Numeric object.

Specified by:

returnTType in interface Function

returnTType

public TType returnTType()

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object