org.basex.query.path
Class Path

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.path.Path
Direct Known Subclasses:
AxisPath, MixedPath

public abstract class Path
extends ParseExpr

Path 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
          Root expression.
 Expr[] steps
          Path steps.
 
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.
 Expr addPreds(QueryContext ctx, VarScope scp, Expr... pred)
          Adds a predicate to the last step.
 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.
protected abstract  Expr compilePath(QueryContext ctx, VarScope scp)
          Compiles the location path.
 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 Path get(InputInfo ii, Expr r, Expr... path)
          Returns a new path instance.
 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.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
Root expression.


steps

public Expr[] steps
Path steps.

Method Detail

get

public static Path get(InputInfo ii,
                       Expr r,
                       Expr... path)
Returns a new path instance.

Parameters:
ii - input info
r - root expression; can be a null reference
path - path steps
Returns:
class instance

checkUp

public final 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

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.

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

optimize

public 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

compilePath

protected abstract Expr compilePath(QueryContext ctx,
                                    VarScope scp)
                             throws QueryException
Compiles the location path.

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.

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

addPreds

public final Expr addPreds(QueryContext ctx,
                           VarScope scp,
                           Expr... pred)
                    throws QueryException
Adds a predicate to the last step.

Parameters:
ctx - query context
scp - variable scope
pred - predicate to be added
Returns:
resulting path instance
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 final 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.

Specified by:
inline in class Expr
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.

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

toString

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

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