uk.ac.ed.epcc.webapp.jdbc.expr

Enum Reduction

java.lang.Object

java.lang.Enum<Reduction>

uk.ac.ed.epcc.webapp.jdbc.expr.Reduction

All Implemented Interfaces:

java.io.Serializable, java.lang.Comparable<Reduction>

public enum Reduction
extends java.lang.Enum<Reduction>

Reduction operators.

The INDEX reduction is equivalent to the SQL GROUP BY CLAUSE, when combined with other Reductions it requests that multiple results should be returned, with reductions only happending across sets of records where the INDEX property is the same.

AVG is a mean value except when doing overlap mapping when it becomes a time average

Enum Constant Summary

Enum Constants

Enum Constant and Description
AVG values are averaged
DISTINCT Count distinct values.
INDEX The INDEX reduction is equivalent to the SQL GROUP BY CLAUSE, when combined with other Reductions it requests that multiple results should be returned, with reductions only happening across sets of records where the INDEX property is the same.
MAX maximum value taken.
MEDIAN median value of values is calcualted
MIN minimum value taken
SELECT SELECT just selects a value without adding to the SQL GROUP BY.
SUM values are summed

Method Summary

Modifier and Type	Method and Description
boolean	customNumber() Can these reductions reductions be implemented by a custom number type
Operator	operator() get a Operator suitable for combing partial results.
static Reduction	valueOf(java.lang.String name) Returns the enum constant of this type with the specified name.
static Reduction[]	values() Returns an array containing the constants of this enum type, in the order they are declared.

Methods inherited from class java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

Methods inherited from class java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

Enum Constant Detail

SUM

public static final Reduction SUM

values are summed

AVG

public static final Reduction AVG

values are averaged

MEDIAN

public static final Reduction MEDIAN

median value of values is calcualted

MIN

public static final Reduction MIN

minimum value taken

MAX

public static final Reduction MAX

maximum value taken.

INDEX

public static final Reduction INDEX

The INDEX reduction is equivalent to the SQL GROUP BY CLAUSE, when combined with other Reductions it requests that multiple results should be returned, with reductions only happening across sets of records where the INDEX property is the same.

SELECT

public static final Reduction SELECT

SELECT just selects a value without adding to the SQL GROUP BY. The expression is assumed to be derivable from the INDEXs or the same for all records.

DISTINCT

public static final Reduction DISTINCT

Count distinct values. This always generates a number whatever is being reduced

Method Detail

values

public static Reduction[] values()

Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:

for (Reduction c : Reduction.values())
    System.out.println(c);

Returns:

an array containing the constants of this enum type, in the order they are declared

valueOf

public static Reduction valueOf(java.lang.String name)

Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)

Parameters:

name - the name of the enum constant to be returned.

Returns:

the enum constant with the specified name

Throws:

java.lang.IllegalArgumentException - if this enum type has no constant with the specified name

java.lang.NullPointerException - if the argument is null

operator

public Operator operator()

get a Operator suitable for combing partial results.

Returns:

Operator

customNumber

public boolean customNumber()

Can these reductions reductions be implemented by a custom number type

Returns: