Package 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 ...

  • Constructor Details

    • Alias

      public Alias(Expression expression, String alias, boolean aliasColumnName)

  • Method Details

    • 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 StringBuilder getUnenclosedSQL(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 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 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 String getSchemaName()
      Description copied from class: Expression
      Get the schema name, or null
      Overrides:
      getSchemaName in class Expression
      Returns:
      the schema name

    • getTableName

      public String getTableName()
      Description copied from class: Expression
      Get the table name, or null
      Overrides:
      getTableName in class Expression
      Returns:
      the table name

    • getColumnName

      public 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