org.basex.query.expr
Class Filter

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.expr.Preds
                  extended by org.basex.query.expr.Filter

public abstract class Filter
extends Preds

Abstract filter expression.

Author:
BaseX Team 2005-12, BSD License, Christian Gruen

Nested Class Summary
 
Nested classes/interfaces inherited from class org.basex.query.expr.Expr
Expr.Flag
 
Field Summary
 Expr root
          Expression.
 
Fields inherited from class org.basex.query.expr.Preds
last, pos, preds
 
Fields inherited from class org.basex.query.expr.ParseExpr
info, size, type
 
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.
abstract  Filter addPred(QueryContext ctx, VarScope scp, Expr p)
          Adds a predicate to the filter.
 void checkUp()
          Checks if all updating expressions are correctly placed.
 Expr compile(QueryContext ctx, VarScope scp)
          Compiles and optimizes the expression, assigns data types and cardinalities.
 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.
static Filter get(InputInfo ii, Expr r, Expr... p)
          Creates a filter expression for the given root and predicates.
 boolean has(Expr.Flag flag)
          Indicates if an expression has the specified compiler property.
 Expr inline(QueryContext ctx, VarScope scp, Var v, Expr e)
          Inlines an expression into this one, replacing all references to the given variable.
 Expr optimize(QueryContext ctx, VarScope scp)
          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.expr.Preds
copy, preds, useIterator
 
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, item, iter, optPre, preEval, size, test, type, value
 
Methods inherited from class org.basex.query.expr.Expr
addText, compEbv, copy, 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
 

Field Detail

root

public Expr root
Expression.

Method Detail

get

public static Filter get(InputInfo ii,
                         Expr r,
                         Expr... p)
Creates a filter expression for the given root and predicates.

Parameters:
ii - input info
r - root expression
p - predicate expressions
Returns:
filter expression

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.

Overrides:
checkUp in class Preds
Throws:
QueryException - query exception

compile

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

Overrides:
compile in class Preds
Parameters:
ctx - query context
scp - variable scope
Returns:
optimized expression
Throws:
QueryException - query exception

addPred

public abstract Filter addPred(QueryContext ctx,
                               VarScope scp,
                               Expr p)
                        throws QueryException
Adds a predicate to the filter.

Parameters:
ctx - query context
scp - variable scope
p - predicate to be added
Returns:
self reference
Throws:
QueryException - query exception

optimize

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

Overrides:
optimize in class Expr
Parameters:
ctx - query context
scp - variable scope
Returns:
optimized expression
Throws:
QueryException - query exception

has

public final 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.

Overrides:
has in class Preds
Parameters:
flag - flag to be found
Returns:
result of check

removable

public final 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.

Overrides:
removable in class Preds
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.

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

inline

public Expr 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.

Overrides:
inline in class Preds
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

plan

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

Overrides:
plan in class Preds
Parameters:
plan - root element

toString

public final java.lang.String toString()
Overrides:
toString in class Preds

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

exprSize

public final 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