ModSQL
Class Aggregate_MinMax

java.lang.Object
  |
  +--ModSQL.AbstractFunction
        |
        +--ModSQL.AbstractAggregate
              |
              +--ModSQL.Aggregate_MinMax

All Implemented Interfaces:

Aggregate, Function

final class Aggregate_MinMax

extends AbstractAggregate

Implementation of SQL aggregate functions MIN() and MAX().

Author:

chris.studholme@utoronto.ca

Field Summary

private boolean	max Function type: true for MAX(), false for MIN().
private Object	minmax Current minimum/maximum value.

Fields inherited from class ModSQL.AbstractAggregate

distinct, distinct_set

Fields inherited from class ModSQL.AbstractFunction

all_constant, constant_non_null, evaluate_order, evaluate_order_array, out_of_order, parameter_constant, parameter_value, parameters, parameters_array

Fields inherited from interface ModSQL.Function

MATCH_BEGINS, MATCH_EQU, MATCH_GT, MATCH_GTE, MATCH_LT, MATCH_LTE, MATCH_NE

Constructor Summary

Aggregate_MinMax(boolean max)
Constructor.

Method Summary

Object	evaluate(boolean aggregate) Evaluate parameter and check for new minimum/maximum.
static Function	forName(String name) Returns a new instance of this class if name is "min" or "max".
String	functionName() Returns "MIN" or "MAX" depending on how this instances was initialized.
int	getMaxResultSize() Return value is the same as for the parameter, or -1 if there is no parameter.
int	getSQLType() This method returns the SQL type of the parameter, or NULL if there is no parameter.
void	optimize() Prepare the function for use.
void	reset() Reset the minimum/maximum object to NULL.

Methods inherited from class ModSQL.AbstractAggregate

addDistinctValue, getDistinctSetSize, isAggregate, isConstant, prefixParameters, registerWith, setDistinct

Methods inherited from class ModSQL.AbstractFunction

addParameter, convertToSQLType, evaluate, evaluateConstantParameters, evaluateOrder, evaluateParameters, evaluateParameters, getCompatableType, getObjectSQLType, getParameter, getParameterCount, postfixParameters, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface ModSQL.Function

addParameter, evaluate, evaluateOrder, getParameter, getParameterCount

Field Detail

max

private boolean max

Function type: true for MAX(), false for MIN().

minmax

private Object minmax

Current minimum/maximum value.

Constructor Detail

Aggregate_MinMax

public Aggregate_MinMax(boolean max)

Constructor.

Parameters:

max - true for MAX(), false for MIN()

Method Detail

forName

public static Function forName(String name)

Returns a new instance of this class if name is "min" or "max". The instance is initialized as needed to represent the desired function.

Parameters:

name - name of function to find

Returns:

instance of this class or null if name does not match

optimize

public void optimize()
              throws SQLException

Prepare the function for use. MIN/MAX accepts at most one parameter and requires a parameter if DISTINCT is requested.

Overrides:

optimize in class AbstractFunction

Throws:

SQLException - if the parameters are invalid

functionName

public String functionName()

Returns "MIN" or "MAX" depending on how this instances was initialized.

Overrides:

functionName in class AbstractFunction

Returns:

name of function

getSQLType

public int getSQLType()
               throws SQLException

This method returns the SQL type of the parameter, or NULL if there is no parameter.

Returns:

SQL type of data to be returned

Throws:

SQLException - if a database-access error occurs

getMaxResultSize

public int getMaxResultSize()
                     throws SQLException

Return value is the same as for the parameter, or -1 if there is no parameter.

Returns:

maximum size of String returned or -1 if unknown

Throws:

SQLException - if a database-access error occurs

reset

public void reset()
           throws SQLException

Reset the minimum/maximum object to NULL.

Overrides:

reset in class AbstractAggregate

Throws:

SQLException - if a database error occurs

evaluate

public Object evaluate(boolean aggregate)
                throws SQLException,
                       EndOfTable

Evaluate parameter and check for new minimum/maximum. This method always returns the current/new minimum/maximum value, regardless of aggregate. If aggregate is true, the parameter is not evaluated.

Parameters:

aggregate - true to return final aggregate value

Returns:

current minimum/maximum object

Throws:

SQLException - if a database-access error occurs

EndOfTable - if thrown by a parameter