JavaFunction (H2 Database Engine wt-1.0.1 API)

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

所有已实现的接口:

FunctionCall
```
public class JavaFunction
extends Expression
implements FunctionCall
```
This class wraps a user-defined function.

构造器概要

构造器
构造器和说明

JavaFunction(FunctionAlias functionAlias, Expression[] args)

构造器
构造器和说明
`JavaFunction(FunctionAlias functionAlias, Expression[] args)`

方法概要

所有方法实例方法具体方法
限定符和类型	方法和说明
`Expression[]`	`getArgs()` Get the function arguments.
`int`	`getCost()` Estimate the cost to process the expression.
`int`	`getDisplaySize()` Get the display size of this expression.
`Expression[]`	`getExpressionColumns(Session session)` If this expression consists of column expressions it should return them.
`String`	`getName()` Get the name of the function.
`long`	`getPrecision()` Get the precision of this expression.
`int`	`getScale()` Get the scale of this expression.
`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[] argList)` Get an empty result set with the column names set.
`boolean`	`isBufferResultSetToLocalTemp()` Should the return value ResultSet be buffered in a local temporary file?
`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.

从类继承的方法 org.h2.expression.Expression
addFilterConditions, createIndexConditions, getAlias, getBooleanValue, getColumnName, getExpressionColumns, getNonAliasExpression, getNotIfPossible, getNullable, getSchemaName, getTableAlias, getTableName, isAutoIncrement, isConstant, isValueSet, isWildcard, toString

从类继承的方法 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- 构造器详细资料
  - JavaFunction
```
public JavaFunction(FunctionAlias functionAlias,
                    Expression[] args)
```
- 方法详细资料
  - getValue
```
public Value getValue(Session session)
```
    从类复制的说明: Expression
    
    Return the resulting value for the current row.
    
    指定者:
    
    getValue 在类中 Expression
    
    参数:
    
    session - the session
    
    返回:
    
    the result
  - getType
```
public int getType()
```
    从类复制的说明: Expression
    
    Return the data type. The data type may not be known before the optimization phase.
    
    指定者:
    
    getType 在接口中 FunctionCall
    
    指定者:
    
    getType 在类中 Expression
    
    返回:
    
    the type
  - mapColumns
```
public void mapColumns(ColumnResolver resolver,
                       int level)
```
    从类复制的说明: Expression
    
    Map the columns of the resolver to expression columns.
    
    指定者:
    
    mapColumns 在类中 Expression
    
    参数:
    
    resolver - the column resolver
    
    level - the subquery nesting level
  - optimize
```
public Expression optimize(Session session)
```
    从类复制的说明: Expression
    
    Try to optimize the expression.
    
    指定者:
    
    optimize 在接口中 FunctionCall
    
    指定者:
    
    optimize 在类中 Expression
    
    参数:
    
    session - the session
    
    返回:
    
    the optimized expression
  - setEvaluatable
```
public void setEvaluatable(TableFilter tableFilter,
                           boolean b)
```
    从类复制的说明: Expression
    
    Tell the expression columns whether the table filter can return values now. This is used when optimizing the query.
    
    指定者:
    
    setEvaluatable 在类中 Expression
    
    参数:
    
    tableFilter - the table filter
    
    b - true if the table filter can return value
  - getScale
```
public int getScale()
```
    从类复制的说明: Expression
    
    Get the scale of this expression.
    
    指定者:
    
    getScale 在类中 Expression
    
    返回:
    
    the scale
  - getPrecision
```
public long getPrecision()
```
    从类复制的说明: Expression
    
    Get the precision of this expression.
    
    指定者:
    
    getPrecision 在类中 Expression
    
    返回:
    
    the precision
  - getDisplaySize
```
public int getDisplaySize()
```
    从类复制的说明: Expression
    
    Get the display size of this expression.
    
    指定者:
    
    getDisplaySize 在类中 Expression
    
    返回:
    
    the display size
  - getSQL
```
public String getSQL()
```
    从类复制的说明: Expression
    
    Get the SQL statement of this expression. This may not always be the original SQL statement, specially after optimization.
    
    指定者:
    
    getSQL 在接口中 FunctionCall
    
    指定者:
    
    getSQL 在类中 Expression
    
    返回:
    
    the SQL statement
  - updateAggregate
```
public void updateAggregate(Session session)
```
    从类复制的说明: 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.
    
    指定者:
    
    updateAggregate 在类中 Expression
    
    参数:
    
    session - the session
  - getName
```
public String getName()
```
    从接口复制的说明: FunctionCall
    
    Get the name of the function.
    
    指定者:
    
    getName 在接口中 FunctionCall
    
    返回:
    
    the name
  - getValueForColumnList
```
public ValueResultSet getValueForColumnList(Session session,
                                            Expression[] argList)
```
    从接口复制的说明: FunctionCall
    
    Get an empty result set with the column names set.
    
    指定者:
    
    getValueForColumnList 在接口中 FunctionCall
    
    参数:
    
    session - the session
    
    argList - the argument list (some arguments may be null)
    
    返回:
    
    the empty result set
  - getArgs
```
public Expression[] getArgs()
```
    从接口复制的说明: FunctionCall
    
    Get the function arguments.
    
    指定者:
    
    getArgs 在接口中 FunctionCall
    
    返回:
    
    argument list
  - isEverything
```
public boolean isEverything(ExpressionVisitor visitor)
```
    从类复制的说明: Expression
    
    Check if this expression and all sub-expressions can fulfill a criteria. If any part returns false, the result is false.
    
    指定者:
    
    isEverything 在类中 Expression
    
    参数:
    
    visitor - the visitor
    
    返回:
    
    if the criteria can be fulfilled
  - getCost
```
public int getCost()
```
    从类复制的说明: Expression
    
    Estimate the cost to process the expression. Used when optimizing the query, to calculate the query plan with the lowest estimated cost.
    
    指定者:
    
    getCost 在类中 Expression
    
    返回:
    
    the estimated cost
  - isDeterministic
```
public boolean isDeterministic()
```
    从接口复制的说明: FunctionCall
    
    Whether the function always returns the same result for the same parameters.
    
    指定者:
    
    isDeterministic 在接口中 FunctionCall
    
    返回:
    
    true if it does
  - getExpressionColumns
```
public Expression[] getExpressionColumns(Session session)
```
    从类复制的说明: Expression
    
    If this expression consists of column expressions it should return them.
    
    覆盖:
    
    getExpressionColumns 在类中 Expression
    
    参数:
    
    session - the session
    
    返回:
    
    array of expression columns if applicable, null otherwise
  - isBufferResultSetToLocalTemp
```
public boolean isBufferResultSetToLocalTemp()
```
    从接口复制的说明: FunctionCall
    
    Should the return value ResultSet be buffered in a local temporary file?
    
    指定者:
    
    isBufferResultSetToLocalTemp 在接口中 FunctionCall
    
    返回:
    
    true if it should be.

类 JavaFunction

构造器概要

方法概要

从类继承的方法 org.h2.expression.Expression

从类继承的方法 java.lang.Object

构造器详细资料

JavaFunction

方法详细资料

getValue

getType

mapColumns

optimize

setEvaluatable

getScale

getPrecision

getDisplaySize

getSQL

updateAggregate

getName

getValueForColumnList

getArgs

isEverything

getCost

isDeterministic

getExpressionColumns

isBufferResultSetToLocalTemp