saffron
Class BuiltinAggregation

java.lang.Object
  |
  +--saffron.BuiltinAggregation

All Implemented Interfaces:

Aggregation

Direct Known Subclasses:

BuiltinAggregation.Count, BuiltinAggregation.MinMax, BuiltinAggregation.Sum

public abstract class BuiltinAggregation

extends Object

implements Aggregation

BuiltinAggregation is a basic aggregator for which special code is generated.

Since:

3 February, 2002

Version:

$Id: //open/saffron/src/main/saffron/BuiltinAggregation.java#2 $

Author:

jhyde

Nested Class Summary

(package private) static class	BuiltinAggregation.Count Count is an aggregator which returns the number of rows which have gone into it.
(package private) static class	BuiltinAggregation.MinMax MinMax implements the "min" and "max" aggregator functions, returning the returns the smallest/largest of the values which go into it.
(package private) static class	BuiltinAggregation.Sum Sum is an aggregator which returns the sum of the values which go into it.

Constructor Summary

BuiltinAggregation()

Method Summary

boolean	canMerge() Whether this aggregation can merge together two accumulators.
static int	count()
static int	count(double v)
static int	count(int v)
static int	count(Object v)
static BuiltinAggregation	create(String name, OJClass[] argTypes) Creates a BuiltinAggregation with a given name and argument types.
(package private) abstract String	getName()
void	implementMerge(Implementor implementor, Rel rel, Expression accumulator, Expression otherAccumulator) Generates (into the current statement list, gleaned by calling implementor's Implementor.getStatementList() method) code to merge two accumulators.
Expression	implementStartAndNext(Implementor implementor, Rel rel, int[] args) This is a default implementation of Aggregation.implementStartAndNext(saffron.opt.Implementor, saffron.rel.Rel, int[]); particular derived classes may do better.
static OJMethod	lookup(String name, OJClass[] argTypes) Returns the builtin aggregator with a given name, if there is one.
static double	max(double v)
static double	max(int v)
static int	max(Object v)
static double	min(double v)
static double	min(int v)
static int	min(Object v)
static double	sum(double v)
static int	sum(int v)

Methods inherited from class java.lang.Object

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

Methods inherited from interface saffron.rel.Aggregation

getParameterTypes, getReturnType, implementNext, implementResult, implementStart

Constructor Detail

BuiltinAggregation

public BuiltinAggregation()

Method Detail

getName

abstract String getName()

create

public static BuiltinAggregation create(String name,
                                        OJClass[] argTypes)

Creates a BuiltinAggregation with a given name and argument types.

canMerge

public boolean canMerge()

Description copied from interface: Aggregation

Whether this aggregation can merge together two accumulators. count can (you just add the accumulators); avg and Nth cannot.

Specified by:

canMerge in interface Aggregation

implementStartAndNext

public Expression implementStartAndNext(Implementor implementor,
                                        Rel rel,
                                        int[] args)

This is a default implementation of Aggregation.implementStartAndNext(saffron.opt.Implementor, saffron.rel.Rel, int[]); particular derived classes may do better.

Specified by:

implementStartAndNext in interface Aggregation

implementMerge

public void implementMerge(Implementor implementor,
                           Rel rel,
                           Expression accumulator,
                           Expression otherAccumulator)

Description copied from interface: Aggregation

Generates (into the current statement list, gleaned by calling implementor's Implementor.getStatementList() method) code to merge two accumulators. For sum(x), this looks like ((saffron.runtime.Holder.int_Holder) accumulator).value += ((saffron.runtime.Holder.int_Holder) other).value.

The method is only called if Aggregation.canMerge() returns true.

Specified by:

implementMerge in interface Aggregation

Parameters:

implementor - a callback object which knows how to generate things

rel - the relational expression which is generating this code

accumulator - the expression which holds the total

otherAccumulator - accumulator to merge in

lookup

public static OJMethod lookup(String name,
                              OJClass[] argTypes)

Returns the builtin aggregator with a given name, if there is one. Note that there is only one builtin aggregator with a particular name ("sum", say), but a particular instance may have different parameter types.

count

public static int count()

count

public static int count(Object v)

count

public static int count(int v)

count

public static int count(double v)

sum

public static int sum(int v)

sum

public static double sum(double v)

min

public static int min(Object v)

min

public static double min(int v)

min

public static double min(double v)

max

public static int max(Object v)

max

public static double max(int v)

max

public static double max(double v)