org.basex.query.gflwor
Class Where

java.lang.Object
  extended by org.basex.data.ExprInfo
      extended by org.basex.query.expr.Expr
          extended by org.basex.query.expr.ParseExpr
              extended by org.basex.query.gflwor.GFLWOR.Clause
                  extended by org.basex.query.gflwor.Where

public final class Where
extends GFLWOR.Clause

GFLWOR where clause, filtering tuples not satisfying the predicate.

Author:
BaseX Team 2005-12, BSD License, Leo Woerteler

Nested Class Summary
 
Nested classes/interfaces inherited from class org.basex.query.expr.Expr
Expr.Flag
 
Field Summary
 
Fields inherited from class org.basex.query.expr.ParseExpr
info, size, type
 
Constructor Summary
Where(Expr e, InputInfo ii)
          Constructor.
 
Method Summary
 boolean accept(ASTVisitor visitor)
          Traverses this expression, notifying the visitor of declared and used variables, and checking the tree for other recursive properties.
 void checkUp()
          Checks if all updating expressions are correctly placed.
 Where compile(QueryContext ctx, VarScope scp)
          Compiles and optimizes the expression, assigns data types and cardinalities.
 Where copy(QueryContext ctx, VarScope scp, IntObjMap<Var> vs)
          Copies an expression.
 VarUsage count(Var v)
          Checks how often a variable is used in this expression.
 int exprSize()
          Counts the number of expressions in this expression's sub-tree.
 boolean has(Expr.Flag flag)
          Indicates if an expression has the specified compiler property.
 GFLWOR.Clause inline(QueryContext ctx, VarScope scp, Var v, Expr e)
          Inlines an expression into this one, replacing all references to the given variable.
 Where optimize(QueryContext cx, VarScope sc)
          Optimizes an already compiled expression without recompiling its sub-expressions.
 void plan(FElem plan)
          Creates an expression tree.
 boolean removable(Var v)
          Checks if the specified variable is replaceable by a context item.
 java.lang.String toString()
           
 
Methods inherited from class org.basex.query.gflwor.GFLWOR.Clause
declares, item, iter, value, vars
 
Methods inherited from class org.basex.query.expr.ParseExpr
checkAdmin, checkAllUp, checkBinary, checkBln, checkColl, checkCreate, checkCtx, checkDbl, checkDBNode, checkEStr, checkEStr, checkFunc, checkItem, checkItr, checkItr, checkMap, checkNode, checkNode, checkNode, checkNoEmpty, checkNoneUp, checkNoUp, checkQNm, checkStr, checkStr, checkStrBin, checkType, checkWrite, compBln, copyType, ebv, optPre, preEval, size, test, type
 
Methods inherited from class org.basex.query.expr.Expr
addText, compEbv, copy, hasFreeVars, indexAccessible, indexEquivalent, inlineAll, isEmpty, isFunction, isItem, isVacuous, isValue, iterable, markTailCalls, sameAs, uses, visitAll
 
Methods inherited from class org.basex.data.ExprInfo
addPlan, addPlan, description, info, planAttr, planElem
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

Where

public Where(Expr e,
             InputInfo ii)
Constructor.

Parameters:
ii - input info
e - predicate expression
Method Detail

plan

public void plan(FElem plan)
Description copied from class: ExprInfo
Creates an expression tree.

Specified by:
plan in class ExprInfo
Parameters:
plan - root element

toString

public java.lang.String toString()
Specified by:
toString in class ExprInfo

has

public boolean has(Expr.Flag flag)
Description copied from class: Expr
Indicates if an expression has the specified compiler property. This method is called by numerous Expr.compile(org.basex.query.QueryContext, org.basex.query.var.VarScope) methods to test properties of sub-expressions. It returns true if at least one test is successful.

Specified by:
has in class Expr
Parameters:
flag - flag to be found
Returns:
result of check

compile

public Where compile(QueryContext ctx,
                     VarScope scp)
              throws QueryException
Description copied from class: Expr
Compiles and optimizes the expression, assigns data types and cardinalities.

Specified by:
compile in class GFLWOR.Clause
Parameters:
ctx - query context
scp - variable scope
Returns:
optimized expression
Throws:
QueryException - query exception

optimize

public Where optimize(QueryContext cx,
                      VarScope sc)
               throws QueryException
Description copied from class: Expr
Optimizes an already compiled expression without recompiling its sub-expressions.

Specified by:
optimize in class GFLWOR.Clause
Parameters:
cx - query context
sc - variable scope
Returns:
optimized expression
Throws:
QueryException - query exception

removable

public boolean removable(Var v)
Description copied from class: Expr
Checks if the specified variable is replaceable by a context item. The following tests might return false: This method is called by GFLWOR.compile(org.basex.query.QueryContext, org.basex.query.var.VarScope) to rewrite where clauses into predicates.

Specified by:
removable in class Expr
Parameters:
v - variable to be replaced
Returns:
result of check

count

public VarUsage count(Var v)
Description copied from class: Expr
Checks how often a variable is used in this expression.

Specified by:
count in class Expr
Parameters:
v - variable to look for
Returns:
how often the variable is used, see VarUsage

inline

public GFLWOR.Clause inline(QueryContext ctx,
                            VarScope scp,
                            Var v,
                            Expr e)
                     throws QueryException
Description copied from class: Expr
Inlines an expression into this one, replacing all references to the given variable.

Specified by:
inline in class GFLWOR.Clause
Parameters:
ctx - query context for recompilation
scp - variable scope for recompilation
v - variable to replace
e - expression to inline
Returns:
resulting expression in something changed, null otherwise
Throws:
QueryException - query exception

copy

public Where copy(QueryContext ctx,
                  VarScope scp,
                  IntObjMap<Var> vs)
Description copied from class: Expr
Copies an expression. Will be useful for inlining functions, or for copying static queries.

Specified by:
copy in class GFLWOR.Clause
Parameters:
ctx - query context
scp - variable scope for creating new variables
vs - mapping from old variable IDs to new variable copies
Returns:
copied expression

accept

public boolean accept(ASTVisitor visitor)
Description copied from class: Expr
Traverses this expression, notifying the visitor of declared and used variables, and checking the tree for other recursive properties.

Specified by:
accept in class Expr
Parameters:
visitor - visitor
Returns:
if the walk should be continued

checkUp

public void checkUp()
             throws QueryException
Description copied from class: Expr
Checks if all updating expressions are correctly placed. This function is only called if any updating expression was found in the query.

Specified by:
checkUp in class Expr
Throws:
QueryException - query exception

exprSize

public int exprSize()
Description copied from class: Expr
Counts the number of expressions in this expression's sub-tree.

Specified by:
exprSize in class Expr
Returns:
number of expressions