Package org.basex.query.expr.gflwor

Class GFLWOR

java.lang.Object

org.basex.query.expr.ExprInfo

org.basex.query.expr.Expr

org.basex.query.expr.ParseExpr

org.basex.query.expr.gflwor.GFLWOR

public final class GFLWOR
extends ParseExpr

General FLWOR expression.

Author:

BaseX Team 2005-21, BSD License, Leo Woerteler

Field Summary

Fields

Modifier and Type	Field	Description
final LinkedList<Clause>	clauses	FLWOR clauses.
Expr	rtrn	Return expression.

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

exprType, info

Constructor Summary

Constructors

Constructor	Description
GFLWOR(InputInfo info, LinkedList<Clause> clauses, Expr rtrn)	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.
void	checkUp()	Checks if the updating semantics are satisfied.
Expr	compile(CompileContext cc)	Compiles and optimizes the expression, assigns types and cardinalities.
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.
String	description()	Returns a string description of the expression.
boolean	equals(Object obj)	This function is e.g.
int	exprSize()	Counts the number of expressions in this expression's sub-tree.
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.
boolean	inlineable(InlineContext ic)	Checks if inlining is possible.
Iter	iter(QueryContext qc)	Evaluates the expression and returns an iterator on the resulting items.
void	markTailCalls(CompileContext cc)	Finds and marks tail calls, enabling TCO.
Expr	optimize(CompileContext cc)	Optimizes an already compiled expression without recompiling its sub-expressions.
void	plan(QueryPlan plan)	Creates a query plan.
void	plan(QueryString qs)	Creates a query string.
Expr	removeOrderBy(CompileContext cc)	Removes order by clauses.
Expr	typeCheck(TypeCheck tc, CompileContext cc)	Tries to push the given type check inside this expression.
boolean	vacuous()	Tests if this is a vacuous expression (empty sequence or error function).
Value	value(QueryContext qc)	Evaluates the expression and returns the resulting value.

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

adoptType, atomValue, checkAllUp, checkNoEmpty, checkNoEmpty, checkNoneUp, checkNoUp, checkType, checkType, checkUp, copyType, ctxValue, ebv, item, 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, data, ddo, funcType, hasFreeVars, indexAccessible, isSimple, mergeEbv, simplifyFor, uses, visitAll

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

toErrorString, toString

Methods inherited from class java.lang.Object

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

Field Details

clauses

public final LinkedList<Clause> clauses

FLWOR clauses.

rtrn

public Expr rtrn

Return expression.

Constructor Details

GFLWOR

public GFLWOR(InputInfo info,
 LinkedList<Clause> clauses,
 Expr rtrn)

Constructor.

Parameters:

info - input info

clauses - FLWOR clauses

rtrn - return expression

Method Details

iter

public Iter iter(QueryContext qc)

Description copied from class: Expr

Evaluates the expression and returns an iterator on the resulting items. The implementation of this method is optional.

Overrides:

iter in class ParseExpr

Parameters:

qc - query context

Returns:

iterator

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

compile

public Expr compile(CompileContext cc)
             throws QueryException

Description copied from class: Expr

Compiles and optimizes the expression, assigns types and cardinalities.

Specified by:

compile in class Expr

Parameters:

cc - compilation context

Returns:

optimized expression

Throws:

QueryException - query exception

optimize

public Expr optimize(CompileContext cc)
              throws QueryException

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

Throws:

QueryException - query exception

vacuous

public boolean vacuous()

Description copied from class: Expr

Tests if this is a vacuous expression (empty sequence or error function). This check is needed for updating queries.

Overrides:

vacuous in class Expr

Returns:

result of check

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.

Specified by:

has in class Expr

Parameters:

flags - flags to be checked

Returns:

result of check

inlineable

public boolean inlineable(InlineContext ic)

Description copied from class: Expr

Checks if inlining is possible. This function is called by InlineContext.inlineable(org.basex.query.expr.Expr...) and: CNode.inlineable(org.basex.query.InlineContext) returns false if the new expression construct new nodes. The following tests might reject inlining if the expression is a context reference:

• Preds.inlineable(org.basex.query.InlineContext)
• Path.inlineable(org.basex.query.InlineContext)
• SimpleMap.inlineable(org.basex.query.InlineContext)
• StaticJavaCall.inlineable(org.basex.query.InlineContext)
• TransformWith.inlineable(org.basex.query.InlineContext)

Specified by:

inlineable in class Expr

Parameters:

ic - inlining context

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

Specified by:

count in class Expr

Parameters:

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

Returns:

number of usages, see VarUsage

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)

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)
• ContextValue.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

removeOrderBy

public Expr removeOrderBy(CompileContext cc)
                   throws QueryException

Removes order by clauses.

Parameters:

cc - compilation context

Returns:

rewritten expression or null

Throws:

QueryException - query exception

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.

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 the updating semantics are satisfied. This function is only called if any updating expression was found in the query.

Specified by:

checkUp in class Expr

Throws:

QueryException - query exception

markTailCalls

public void markTailCalls(CompileContext cc)

Description copied from class: Expr

Finds and marks tail calls, enabling TCO.

Overrides:

markTailCalls in class Expr

Parameters:

cc - compilation context, null if the changes should not be reported

exprSize

public int exprSize()

Description copied from class: Expr

Counts the number of expressions in this expression's sub-tree. This method is e.g. called by StaticFunc.inline(org.basex.query.expr.Expr[], org.basex.query.CompileContext) to check if an expression is small enough to be inlined.

Specified by:

exprSize in class Expr

Returns:

number of expressions

typeCheck

public Expr typeCheck(TypeCheck tc,
 CompileContext cc)
               throws QueryException

Description copied from class: Expr

Tries to push the given type check inside this expression.

Overrides:

typeCheck in class Expr

Parameters:

tc - type check to push into the expression

cc - compilation context

Returns:

the resulting expression if successful, null otherwise

Throws:

QueryException - query exception

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

description

public String description()

Description copied from class: ExprInfo

Returns a string description of the expression. This method is only called by error messages. Contrary to the ExprInfo.toString() method, arguments are not included in the output.

Overrides:

description in class ExprInfo

Returns:

result of check

plan

public void plan(QueryPlan plan)

Description copied from class: ExprInfo

Creates a query plan.

Specified by:

plan in class ExprInfo

Parameters:

plan - expression plan

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