org.h2.expression

类 Wildcard

java.lang.Object

org.h2.expression.Expression

org.h2.expression.Wildcard

public class Wildcard
extends Expression

A wildcard expression as in SELECT * FROM TEST. This object is only used temporarily during the parsing phase, and later replaced by column expressions.

构造器概要

构造器

构造器和说明
Wildcard(String schema, String table)

方法概要

限定符和类型	方法和说明
int	getCost() Estimate the cost to process the expression.
int	getDisplaySize() Get the display size of this expression.
long	getPrecision() Get the precision of this expression.
int	getScale() Get the scale of this expression.
String	getSchemaName() Get the schema name, or null
String	getSQL() Get the SQL statement of this expression.
String	getTableAlias() Get the table alias name or null if this expression does not represent a column.
int	getType() Return the data type.
Value	getValue(Session session) Return the resulting value for the current row.
boolean	isEverything(ExpressionVisitor visitor) Check if this expression and all sub-expressions can fulfill a criteria.
boolean	isWildcard() Only returns true if the expression is a wildcard.
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, getExpressionColumns, getNonAliasExpression, getNotIfPossible, getNullable, getTableName, isAutoIncrement, isConstant, isValueSet, 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

Wildcard

public Wildcard(String schema,
                String table)

方法详细资料

isWildcard

public boolean isWildcard()

从类复制的说明: Expression

Only returns true if the expression is a wildcard.

覆盖:

isWildcard 在类中 Expression

返回:

if this expression is a wildcard

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

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

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

getTableAlias

public String getTableAlias()

从类复制的说明: Expression

Get the table alias name or null if this expression does not represent a column.

覆盖:

getTableAlias 在类中 Expression

返回:

the table alias name

getSchemaName

public String getSchemaName()

从类复制的说明: Expression

Get the schema name, or null

覆盖:

getSchemaName 在类中 Expression

返回:

the schema name

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