ModSQL
Class Operator_Exists

java.lang.Object
  |
  +--ModSQL.AbstractFunction
        |
        +--ModSQL.Operator
              |
              +--ModSQL.Operator_Exists

All Implemented Interfaces:

Function

final class Operator_Exists

extends Operator

Implementation of EXISTS operator.

Author:

chris.studholme@utoronto.ca

Field Summary

private Boolean	constant_result If is_constant, this variable holds the constant result.
private boolean	is_constant True if operator returns a constant value (table is constant).
private Table	table Table to scan.

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

(package private)

Operator_Exists()

Method Summary

Object	evaluate(boolean aggregate) Evaluate table and compute the function.
Object	evaluate(int match_op, Object match_value) Evaluate table and compute the function.
String	functionName() Returns "#EXISTS".
int	getMaxResultSize() Returns -1 as this operator will never return a String object.
int	getSQLType() Returns Types.BIT.
boolean	isConstant() Returns true if the table is constant.
void	optimize() Prepare the function for use.
String	postfixParameters() Returns table as string if set.
void	registerWith(Object o) Since the table is not a regular parameter, this method is need to ensure the table can register itself with objects as needed.
void	setTable(Table table) Specify the table to be scanned.

Methods inherited from class ModSQL.Operator

addAllParameters, addAllParametersNegate, addAllParametersNot, removeDoubleNegation, removeDoubleNot

Methods inherited from class ModSQL.AbstractFunction

addParameter, convertToSQLType, evaluateConstantParameters, evaluateOrder, evaluateParameters, evaluateParameters, getCompatableType, getObjectSQLType, getParameter, getParameterCount, isAggregate, prefixParameters, reset, toString

Methods inherited from class java.lang.Object

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

Field Detail

table

private Table table

Table to scan.

is_constant

private boolean is_constant

True if operator returns a constant value (table is constant).

constant_result

private Boolean constant_result

If is_constant, this variable holds the constant result.

Constructor Detail

Operator_Exists

Operator_Exists()

Method Detail

setTable

public void setTable(Table table)

Specify the table to be scanned.

Parameters:

table - table to scan

registerWith

public void registerWith(Object o)
                  throws SQLException

Since the table is not a regular parameter, this method is need to ensure the table can register itself with objects as needed.

Overrides:

registerWith in class AbstractFunction

Parameters:

o - object to register with

Throws:

SQLException - if a database error occurs

optimize

public void optimize()
              throws SQLException

Prepare the function for use. This method ensures that there are no parameters (except the table). If the table is constant, it is checked for rows and the result is stored.

Overrides:

optimize in class AbstractFunction

Throws:

SQLException - if the parameters are invalid

functionName

public String functionName()

Returns "#EXISTS".

Overrides:

functionName in class AbstractFunction

Returns:

name of function

postfixParameters

public String postfixParameters()

Returns table as string if set.

Overrides:

postfixParameters in class AbstractFunction

Returns:

table as string

isConstant

public boolean isConstant()

Returns true if the table is constant.

Overrides:

isConstant in class AbstractFunction

Returns:

true if the value returned is constant

getSQLType

public int getSQLType()

Returns Types.BIT.

Returns:

SQL type of data to be returned

getMaxResultSize

public int getMaxResultSize()

Returns -1 as this operator will never return a String object.

Returns:

maximum size of String returned or -1 if unknown

evaluate

public Object evaluate(boolean aggregate)
                throws SQLException,
                       EndOfTable

Evaluate table and compute the function.

Parameters:

aggregate - ignored

Returns:

result object

Throws:

SQLException - if a database-access error occurs

EndOfTable - if thrown by a parameter

evaluate

public Object evaluate(int match_op,
                       Object match_value)
                throws SQLException,
                       EndOfTable

Evaluate table and compute the function.

Overrides:

evaluate in class AbstractFunction

Parameters:

match_op - how the value should be matched

match_value - desired value

Returns:

result object

Throws:

SQLException - if a database-access error occurs

EndOfTable - if thrown by a parameter