org.basex.query.expr
Class Group

java.lang.Object
  extended by org.basex.query.ExprInfo
      extended by org.basex.query.expr.Expr
          extended by org.basex.query.expr.Group

public final class Group
extends Expr

Implementation of the group by clause.

Author:
Workgroup DBIS, University of Konstanz 2005-10, ISC License, Michael Seiferle

Nested Class Summary
 
Nested classes/interfaces inherited from class org.basex.query.expr.Expr
Expr.Use
 
Constructor Summary
Group(Grp[] g)
          Constructor.
 
Method Summary
 void add(QueryContext ctx)
          Adds the items to be grouped.
 Expr comp(QueryContext ctx)
          Optimizes and compiles the expression.
 Iter iter(QueryContext ctx)
          Evaluates the expression and returns an iterator on the resulting items.
 void plan(Serializer ser)
          Recursively sends the abstract syntax of this expression to the specified serializer.
 Group remove(Var v)
          Removes the specified variable in a sub expression.
 String toString()
           
 boolean uses(Expr.Use use, QueryContext ctx)
          Indicates if an expression uses the specified type.
 
Methods inherited from class org.basex.query.expr.Expr
addText, atomic, checkCtx, checkDbl, checkItr, duplicates, e, ebv, i, indexAccessible, indexEquivalent, removable, returned, sameAs, size, test, v
 
Methods inherited from class org.basex.query.ExprInfo
color, info, name
 
Methods inherited from class java.lang.Object
equals, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

Group

public Group(Grp[] g)
Constructor.

Parameters:
g - groups
Method Detail

comp

public Expr comp(QueryContext ctx)
          throws QueryException
Description copied from class: Expr
Optimizes and compiles the expression.

Specified by:
comp in class Expr
Parameters:
ctx - query context
Returns:
optimized Expression
Throws:
QueryException - query exception

iter

public Iter iter(QueryContext ctx)
Description copied from class: Expr
Evaluates the expression and returns an iterator on the resulting items. If this method is not overwritten, Expr.atomic(org.basex.query.QueryContext) must be implemented.

Overrides:
iter in class Expr
Parameters:
ctx - query context
Returns:
resulting item

add

public void add(QueryContext ctx)
         throws QueryException
Adds the items to be grouped.

Parameters:
ctx - query context
Throws:
QueryException - query exception

uses

public boolean uses(Expr.Use use,
                    QueryContext ctx)
Description copied from class: Expr
Indicates if an expression uses the specified type. Called by the compiler to perform certain optimizations. true is returned by default and thus assumed as "worst-case".

Specified by:
uses in class Expr
Parameters:
use - use type to be checked
ctx - query context
Returns:
result of check

remove

public Group remove(Var v)
Description copied from class: Expr
Removes the specified variable in a sub expression.

Overrides:
remove in class Expr
Parameters:
v - variable to be removed
Returns:
expression with removed variable

plan

public void plan(Serializer ser)
          throws IOException
Description copied from class: ExprInfo
Recursively sends the abstract syntax of this expression to the specified serializer.

Specified by:
plan in class ExprInfo
Parameters:
ser - serializer
Throws:
IOException - I/O exception

toString

public String toString()
Specified by:
toString in class ExprInfo