org.h2.expression

Class Alias

java.lang.Object

org.h2.expression.Expression

org.h2.expression.Alias

All Implemented Interfaces:

HasSQL, Typed

public final class Alias
extends Expression

A column alias as in SELECT 'Hello' AS NAME ...

Field Summary

Fields inherited from class org.h2.expression.Expression

AUTO_PARENTHESES, MAP_IN_AGGREGATE, MAP_IN_WINDOW, MAP_INITIAL, WITH_PARENTHESES, WITHOUT_PARENTHESES

Fields inherited from interface org.h2.util.HasSQL

ADD_PLAN_INFORMATION, DEFAULT_SQL_FLAGS, NO_CASTS, QUOTE_ONLY_WHEN_REQUIRED, REPLACE_LOBS_FOR_TRACE, TRACE_SQL_FLAGS

Constructor Summary

Constructors

Constructor and Description
Alias(Expression expression, java.lang.String alias, boolean aliasColumnName)

Method Summary

Modifier and Type	Method and Description
java.lang.String	getAlias(SessionLocal session, int columnIndex) Get the alias name of a column or SQL expression if it is not an aliased expression.
java.lang.String	getColumnName(SessionLocal session, int columnIndex) Get the column name or alias name of this expression.
java.lang.String	getColumnNameForView(SessionLocal session, int columnIndex) Get the column name of this expression for a view.
int	getCost() Estimate the cost to process the expression.
Expression	getNonAliasExpression() Returns the main expression, skipping aliases.
int	getNullable() Check whether this expression is a column and can store NULL.
java.lang.String	getSchemaName() Get the schema name, or null
java.lang.String	getTableName() Get the table name, or null
TypeInfo	getType() Returns the data type.
java.lang.StringBuilder	getUnenclosedSQL(java.lang.StringBuilder builder, int sqlFlags) Get the SQL statement of this expression.
Value	getValue(SessionLocal 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	isIdentity() Check if this is an identity column.
void	mapColumns(ColumnResolver resolver, int level, int state) Map the columns of the resolver to expression columns.
Expression	optimize(SessionLocal 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(SessionLocal session, int stage) Update an aggregate value.

Methods inherited from class org.h2.expression.Expression

addFilterConditions, createIndexConditions, getBooleanValue, getEnclosedSQL, getNotIfPossible, getSQL, getSQL, getSQL, getSQL, getSubexpression, getSubexpressionCount, getTableAlias, getWhenSQL, getWhenValue, isConstant, isNullConstant, isValueSet, isWhenConditionOperand, needParentheses, optimizeCondition, toString, writeExpressions, writeExpressions

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.h2.util.HasSQL

getTraceSQL

Constructor Detail

Alias

public Alias(Expression expression,
             java.lang.String alias,
             boolean aliasColumnName)

Method Detail

getNonAliasExpression

public Expression getNonAliasExpression()

Description copied from class: Expression

Returns the main expression, skipping aliases.

Overrides:

getNonAliasExpression in class Expression

Returns:

the expression

getValue

public Value getValue(SessionLocal session)

Description copied from class: Expression

Return the resulting value for the current row.

Specified by:

getValue in class Expression

Parameters:

session - the session

Returns:

the result

getType

public TypeInfo getType()

Description copied from class: Expression

Returns the data type. The data type may be unknown before the optimization phase.

Specified by:

getType in interface Typed

Specified by:

getType in class Expression

Returns:

the data type

mapColumns

public void mapColumns(ColumnResolver resolver,
                       int level,
                       int state)

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

state - current state for nesting checks, initial value is Expression.MAP_INITIAL

optimize

public Expression optimize(SessionLocal session)

Description copied from class: Expression

Try to optimize the expression.

Specified by:

optimize in class Expression

Parameters:

session - the session

Returns:

the optimized expression

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

isIdentity

public boolean isIdentity()

Description copied from class: Expression

Check if this is an identity column.

Overrides:

isIdentity in class Expression

Returns:

true if it is an identity column

getUnenclosedSQL

public java.lang.StringBuilder getUnenclosedSQL(java.lang.StringBuilder builder,
                                                int sqlFlags)

Description copied from class: Expression

Get the SQL statement of this expression. This may not always be the original SQL statement, especially after optimization. Enclosing '(' and ')' are never appended.

Specified by:

getUnenclosedSQL in class Expression

Parameters:

builder - string builder

sqlFlags - formatting flags

Returns:

the specified string builder

updateAggregate

public void updateAggregate(SessionLocal session,
                            int stage)

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

stage - select stage

getAlias

public java.lang.String getAlias(SessionLocal session,
                                 int columnIndex)

Description copied from class: Expression

Get the alias name of a column or SQL expression if it is not an aliased expression.

Overrides:

getAlias in class Expression

Parameters:

session - the session

columnIndex - 0-based column index

Returns:

the alias name

getColumnNameForView

public java.lang.String getColumnNameForView(SessionLocal session,
                                             int columnIndex)

Description copied from class: Expression

Get the column name of this expression for a view.

Overrides:

getColumnNameForView in class Expression

Parameters:

session - the session

columnIndex - 0-based column index

Returns:

the column name for a view

getNullable

public int getNullable()

Description copied from class: Expression

Check whether this expression is a column and can store NULL.

Overrides:

getNullable in class Expression

Returns:

whether NULL is allowed

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

getSchemaName

public java.lang.String getSchemaName()

Description copied from class: Expression

Get the schema name, or null

Overrides:

getSchemaName in class Expression

Returns:

the schema name

getTableName

public java.lang.String getTableName()

Description copied from class: Expression

Get the table name, or null

Overrides:

getTableName in class Expression

Returns:

the table name

getColumnName

public java.lang.String getColumnName(SessionLocal session,
                                      int columnIndex)

Description copied from class: Expression

Get the column name or alias name of this expression.

Overrides:

getColumnName in class Expression

Parameters:

session - the session

columnIndex - 0-based column index

Returns:

the column name