org.h2.expression
Class JavaFunction

java.lang.Object
  org.h2.expression.Expression
      org.h2.expression.JavaFunction

All Implemented Interfaces:

FunctionCall

public class JavaFunction
extends Expression
implements FunctionCall

This class wraps a user-defined function.

Constructor Summary

JavaFunction(FunctionAlias functionAlias, Expression[] args)

Method Summary

Expression[]	getArgs() Get the function arguments.
int	getCost() Estimate the cost to process the expression.
int	getDisplaySize() Get the display size of this expression.
java.lang.String	getName() Get the name of the function.
int	getParameterCount() Get the number of parameters.
long	getPrecision() Get the precision of this expression.
int	getScale() Get the scale of this expression.
java.lang.String	getSQL() Get the SQL statement of this expression.
int	getType() Return the data type.
Value	getValue(Session session) Return the resulting value for the current row.
ValueResultSet	getValueForColumnList(Session session, Expression[] args) Get an empty result set with the column names set.
boolean	isDeterministic() Whether the function always returns the same result for the same parameters.
boolean	isEverything(ExpressionVisitor visitor) Check if this expression and all sub-expressions can fulfill a criteria.
void	mapColumns(ColumnResolver resolver, int level) Map the columns of the resolver to expression columns.
Expression	optimize(Session session) Try to optimize the expression.
void	setEvaluatable(TableFilter tableFilter, boolean b) Tell the expression columns whether the table filter can return values now.
void	updateAggregate(Session session) Update an aggregate value.

Methods inherited from class org.h2.expression.Expression

addFilterConditions, createIndexConditions, getAlias, getBooleanValue, getColumnName, getNonAliasExpression, getNotIfPossible, getNullable, getSchemaName, getTableAlias, getTableName, isAutoIncrement, isConstant, isEverything, isValueSet, isWildcard, optimizeInJoin, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

JavaFunction

public JavaFunction(FunctionAlias functionAlias,
                    Expression[] args)
             throws java.sql.SQLException

Throws:

java.sql.SQLException

Method Detail

getValue

public Value getValue(Session session)
               throws java.sql.SQLException

Description copied from class: Expression

Return the resulting value for the current row.

Specified by:

getValue in interface FunctionCall

Specified by:

getValue in class Expression

Parameters:

session - the session

Returns:

the result

Throws:

java.sql.SQLException

getType

public int getType()

Description copied from class: Expression

Return the data type. The data type may not be known before the optimization phase.

Specified by:

getType in interface FunctionCall

Specified by:

getType in class Expression

Returns:

the type

mapColumns

public void mapColumns(ColumnResolver resolver,
                       int level)
                throws java.sql.SQLException

Description copied from class: Expression

Map the columns of the resolver to expression columns.

Specified by:

mapColumns in class Expression

Parameters:

resolver - the column resolver

level - the subquery nesting level

Throws:

java.sql.SQLException

optimize

public Expression optimize(Session session)
                    throws java.sql.SQLException

Description copied from class: Expression

Try to optimize the expression.

Specified by:

optimize in interface FunctionCall

Specified by:

optimize in class Expression

Parameters:

session - the session

Returns:

the optimized expression

Throws:

java.sql.SQLException

setEvaluatable

public void setEvaluatable(TableFilter tableFilter,
                           boolean b)

Description copied from class: Expression

Tell the expression columns whether the table filter can return values now. This is used when optimizing the query.

Specified by:

setEvaluatable in class Expression

Parameters:

tableFilter - the table filter

b - true if the table filter can return value

getScale

public int getScale()

Description copied from class: Expression

Get the scale of this expression.

Specified by:

getScale in class Expression

Returns:

the scale

getPrecision

public long getPrecision()

Description copied from class: Expression

Get the precision of this expression.

Specified by:

getPrecision in class Expression

Returns:

the precision

getDisplaySize

public int getDisplaySize()

Description copied from class: Expression

Get the display size of this expression.

Specified by:

getDisplaySize in class Expression

Returns:

the display size

getSQL

public java.lang.String getSQL()

Description copied from class: Expression

Get the SQL statement of this expression. This may not always be the original SQL statement, specially after optimization.

Specified by:

getSQL in interface FunctionCall

Specified by:

getSQL in class Expression

Returns:

the SQL statement

updateAggregate

public void updateAggregate(Session session)
                     throws java.sql.SQLException

Description copied from class: Expression

Update an aggregate value. This method is called at statement execution time. It is usually called once for each row, but if the expression is used multiple times (for example in the column list, and as part of the HAVING expression) it is called multiple times - the row counter needs to be used to make sure the internal state is only updated once.

Specified by:

updateAggregate in class Expression

Parameters:

session - the session

Throws:

java.sql.SQLException

getName

public java.lang.String getName()

Description copied from interface: FunctionCall

Get the name of the function.

Specified by:

getName in interface FunctionCall

Returns:

the name

getParameterCount

public int getParameterCount()

Description copied from interface: FunctionCall

Get the number of parameters.

Specified by:

getParameterCount in interface FunctionCall

Returns:

the number of parameters

getValueForColumnList

public ValueResultSet getValueForColumnList(Session session,
                                            Expression[] args)
                                     throws java.sql.SQLException

Description copied from interface: FunctionCall

Get an empty result set with the column names set.

Specified by:

getValueForColumnList in interface FunctionCall

Parameters:

session - the session

args - the argument list (some arguments may be null)

Returns:

the empty result set

Throws:

java.sql.SQLException

getArgs

public Expression[] getArgs()

Description copied from interface: FunctionCall

Get the function arguments.

Specified by:

getArgs in interface FunctionCall

Returns:

argument list

isEverything

public boolean isEverything(ExpressionVisitor visitor)

Description copied from class: Expression

Check if this expression and all sub-expressions can fulfill a criteria. If any part returns false, the result is false.

Specified by:

isEverything in class Expression

Parameters:

visitor - the visitor

Returns:

if the criteria can be fulfilled

getCost

public int getCost()

Description copied from class: Expression

Estimate the cost to process the expression. Used when optimizing the query, to calculate the query plan with the lowest estimated cost.

Specified by:

getCost in class Expression

Returns:

the estimated cost

isDeterministic

public boolean isDeterministic()

Description copied from interface: FunctionCall

Whether the function always returns the same result for the same parameters.

Specified by:

isDeterministic in interface FunctionCall

Returns:

true if it does