Package org.basex.query.expr

Class ContextValue

java.lang.Object

org.basex.query.expr.ExprInfo

org.basex.query.expr.Expr

org.basex.query.expr.ParseExpr

org.basex.query.expr.Simple

org.basex.query.expr.ContextValue

public final class ContextValue
extends Simple

Context value.

Author:

BaseX Team 2005-21, BSD License, Christian Gruen

Field Summary

Fields inherited from class org.basex.query.expr.ParseExpr

exprType, info

Constructor Summary

Constructors

Constructor	Description
ContextValue(InputInfo info)	Constructor.

Method Summary

Modifier and Type	Method	Description
boolean	accept(ASTVisitor visitor)	Traverses this expression, notifying the visitor of declared and used variables, and checking the tree for other recursive properties.
Expr	copy(CompileContext cc, IntObjMap<Var> vm)	Copies an expression.
VarUsage	count(Var var)	Checks how often a variable or context reference is used in this expression.
Data	data()	Returns the data reference bound to this expression.
void	data(Data dt)	Assigns a data reference, if supported.
boolean	equals(Object obj)	This function is e.g.
static Expr	get(CompileContext cc, InputInfo ii)	Creates a new, optimized context value expression.
boolean	has(Flag... flags)	Indicates if an expression has one of the specified compiler properties.
Expr	inline(InlineContext ic)	Inlines an expression into this one, replacing all variable or context references.
Expr	optimize(CompileContext cc)	Optimizes an already compiled expression without recompiling its sub-expressions.
void	plan(QueryString qs)	Creates a query string.
Value	value(QueryContext qc)	Evaluates the expression and returns the resulting value.

Methods inherited from class org.basex.query.expr.Simple

checkUp, compile, exprSize, inlineable, plan

Methods inherited from class org.basex.query.expr.ParseExpr

adoptType, atomValue, checkAllUp, checkNoEmpty, checkNoEmpty, checkNoneUp, checkNoUp, checkType, checkType, checkUp, copyType, ctxValue, ebv, item, iter, refineType, seqType, size, test, toArray, toArray, toAtomItem, toB64, toB64, toBin, toBin, toBoolean, toBoolean, toBytes, toBytes, toDouble, toDouble, toElem, toFloat, toFunc, toItem, toItem, toLong, toLong, toMap, toMap, toNode, toNode, toNodeOrNull, toNumber, toNumberOrNull, toQNm, toQNm, toToken, toToken, toTokenOrNull, toZeroToken

Methods inherited from class org.basex.query.expr.Expr

arg, args, atomItem, atomIter, ddo, funcType, hasFreeVars, indexAccessible, isSimple, markTailCalls, mergeEbv, simplifyFor, typeCheck, uses, vacuous, visitAll

Methods inherited from class org.basex.query.expr.ExprInfo

description, toErrorString, toString

Methods inherited from class java.lang.Object

clone, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Details

ContextValue

public ContextValue(InputInfo info)

Constructor.

Parameters:

info - input info

Method Details

get

public static Expr get(CompileContext cc,
 InputInfo ii)

Creates a new, optimized context value expression.

Parameters:

cc - compilation context

ii - input info

Returns:

optimized expression

optimize

public Expr optimize(CompileContext cc)

Description copied from class: Expr

Optimizes an already compiled expression without recompiling its sub-expressions.

Overrides:

optimize in class Expr

Parameters:

cc - compilation context

Returns:

optimized expression

value

public Value value(QueryContext qc)
            throws QueryException

Description copied from class: Expr

Evaluates the expression and returns the resulting value. If this method is not implemented, Expr.item(QueryContext, InputInfo) must be implemented instead.

Overrides:

value in class ParseExpr

Parameters:

qc - query context

Returns:

value

Throws:

QueryException - query exception

has

public boolean has(Flag... flags)

Description copied from class: Expr

Indicates if an expression has one of the specified compiler properties. This method must only be called at compile time. It is invoked to test properties of sub-expressions. It returns true if at least flag matches an expression.

Overrides:

has in class Simple

Parameters:

flags - flags to be checked

Returns:

result of check

count

public VarUsage count(Var var)

Description copied from class: Expr

Checks how often a variable or context reference is used in this expression. This function is called by:

• Closure.optimize(org.basex.query.CompileContext)
• GFLWOR.inlineForLet(org.basex.query.CompileContext)
• GFLWOR.optimizePos(org.basex.query.CompileContext)
• GFLWOR.simplify(org.basex.query.CompileContext)
• GFLWOR.unusedVars(org.basex.query.CompileContext)
• SimpleMap.optimize(org.basex.query.CompileContext)
• TypeswitchGroup.optimize(org.basex.query.CompileContext)

Overrides:

count in class Simple

Parameters:

var - variable (Var reference) or context (null) to inline

Returns:

number of usages, see VarUsage

inline

public Expr inline(InlineContext ic)
            throws QueryException

Description copied from class: Expr

Inlines an expression into this one, replacing all variable or context references. This function is called by InlineContext.inline(Expr) (see invocations of this functions for further inlinings). The variable reference is replaced in:

• OrderBy.inline(org.basex.query.InlineContext)
• VarRef.inline(org.basex.query.InlineContext)

The context is replaced in:

• ContextFn.inline(org.basex.query.InlineContext)
• inline(org.basex.query.InlineContext)
• Arr.inline(org.basex.query.InlineContext)

Specified by:

inline in class Expr

Parameters:

ic - inlining context

Returns:

resulting expression if something has changed, null otherwise

Throws:

QueryException - query exception

data

public Data data()

Description copied from class: Expr

Returns the data reference bound to this expression. This method is currently overwritten by DBNode, DBNodeSeq, AxisPath and VarRef.

Overrides:

data in class Expr

Returns:

data reference (can be null)

data

public void data(Data dt)

Description copied from class: Expr

Assigns a data reference, if supported.

Overrides:

data in class Expr

Parameters:

dt - data reference

copy

public Expr copy(CompileContext cc,
 IntObjMap<Var> vm)

Description copied from class: Expr

Copies an expression. Used for inlining functions, or for copying static queries. It is utilized by VarRef.inline(org.basex.query.InlineContext), FuncItem.inline(org.basex.query.expr.Expr[], org.basex.query.CompileContext), Closure.inline(org.basex.query.InlineContext) and StaticFunc.inline(org.basex.query.expr.Expr[], org.basex.query.CompileContext).

Specified by:

copy in class Expr

Parameters:

cc - compilation context

vm - mapping from old variable IDs to new variable copies. Required by Closure.copy(org.basex.query.CompileContext, org.basex.util.hash.IntObjMap<org.basex.query.var.Var>) and VarRef.copy(org.basex.query.CompileContext, org.basex.util.hash.IntObjMap<org.basex.query.var.Var>)

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.

Overrides:

accept in class Simple

Parameters:

visitor - visitor

Returns:

if the walk should be continued

equals

public boolean equals(Object obj)

Description copied from class: Expr

This function is e.g. called by:

• If.optimize(CompileContext), Switch.optimize(CompileContext), Typeswitch.optimize(CompileContext), in order to discard identical expressions.
• CmpR.mergeEbv(Expr, boolean, CompileContext) or CmpSR.mergeEbv(Expr, boolean, CompileContext), in order to merge expressions with identical input.
• CmpG.optimize(CompileContext) or CmpV.optimize(CompileContext), in order to pre-evaluate equality tests.
• CmpG.optimize(CompileContext) or Pos.get(Expr, CmpV.OpV, InputInfo, CompileContext), in order to compare the start and end value.
• PathCache, in order to find identical root values at runtime.

Specified by:

equals in class Expr

plan

public void plan(QueryString qs)

Description copied from class: ExprInfo

Creates a query string.

Specified by:

plan in class ExprInfo

Parameters:

qs - query string builder