ValueExpression (H2 Database Engine wt-1.0.1 API)

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

public class ValueExpression
extends Expression

An expression representing a constant value.

方法概要

所有方法静态方法实例方法具体方法
限定符和类型	方法和说明
`void`	`createIndexConditions(Session session, TableFilter filter)` Create index conditions if possible and attach them to the table filter.
`static ValueExpression`	`get(Value value)` Create a new expression with the given value.
`int`	`getCost()` Estimate the cost to process the expression.
`static ValueExpression`	`getDefault()` Get the DEFAULT 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.
`Expression`	`getNotIfPossible(Session session)` If it is possible, return the negated expression.
`static ValueExpression`	`getNull()` Get the NULL expression.
`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.
`boolean`	`isConstant()` Check if this expression will always return the same value.
`boolean`	`isEverything(ExpressionVisitor visitor)` Check if this expression and all sub-expressions can fulfill a criteria.
`boolean`	`isValueSet()` Is the value of a parameter set.
`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, getAlias, getBooleanValue, getColumnName, getExpressionColumns, getNonAliasExpression, getNullable, getSchemaName, getTableAlias, getTableName, isAutoIncrement, isWildcard, toString

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

- 方法详细资料
  - getNull
```
public static ValueExpression getNull()
```
    Get the NULL expression.
    
    返回:
    
    the NULL expression
  - getDefault
```
public static ValueExpression getDefault()
```
    Get the DEFAULT expression.
    
    返回:
    
    the DEFAULT expression
  - get
```
public static ValueExpression get(Value value)
```
    Create a new expression with the given value.
    
    参数:
    
    value - the value
    
    返回:
    
    the expression
  - 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 在类中 Expression
    
    返回:
    
    the type
  - createIndexConditions
```
public void createIndexConditions(Session session,
                                  TableFilter filter)
```
    从类复制的说明: Expression
    
    Create index conditions if possible and attach them to the table filter.
    
    覆盖:
    
    createIndexConditions 在类中 Expression
    
    参数:
    
    session - the session
    
    filter - the table filter
  - getNotIfPossible
```
public Expression getNotIfPossible(Session session)
```
    从类复制的说明: Expression
    
    If it is possible, return the negated expression. This is used to optimize NOT expressions: NOT ID>10 can be converted to ID<=10. Returns null if negating is not possible.
    
    覆盖:
    
    getNotIfPossible 在类中 Expression
    
    参数:
    
    session - the session
    
    返回:
    
    the negated expression, or null
  - 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 在类中 Expression
    
    参数:
    
    session - the session
    
    返回:
    
    the optimized expression
  - isConstant
```
public boolean isConstant()
```
    从类复制的说明: Expression
    
    Check if this expression will always return the same value.
    
    覆盖:
    
    isConstant 在类中 Expression
    
    返回:
    
    if the expression is constant
  - isValueSet
```
public boolean isValueSet()
```
    从类复制的说明: Expression
    
    Is the value of a parameter set.
    
    覆盖:
    
    isValueSet 在类中 Expression
    
    返回:
    
    true if set
  - 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
  - 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
  - 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

类 ValueExpression

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

方法详细资料

getNull

getDefault

get

getValue

getType

createIndexConditions

getNotIfPossible

mapColumns

optimize

isConstant

isValueSet

setEvaluatable

getScale

getPrecision

getDisplaySize

getSQL

updateAggregate

isEverything

getCost

getExpressionColumns