Package org.h2.expression

Class Alias

  • All Implemented Interfaces:
    HasSQL, Typed
    public final class Alias
extends Expression
    A column alias as in SELECT 'Hello' AS NAME ...

    • Field Detail

      • alias

        private final java.lang.String alias

      • aliasColumnName

        private final boolean aliasColumnName

    • Constructor Detail

      • Alias

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

    • Method Detail

      • 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