org.basex.query.expr
Class Group

java.lang.Object
  org.basex.query.ExprInfo
      org.basex.query.expr.Expr
          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