Package org.basex.query.expr.path

Class Path

java.lang.Object

org.basex.query.expr.ExprInfo

org.basex.query.expr.Expr

org.basex.query.expr.ParseExpr

org.basex.query.expr.path.Path

Direct Known Subclasses:

AxisPath, MixedPath

public abstract class Path
extends ParseExpr

Path expression.

Author:

BaseX Team 2005-21, BSD License, Christian Gruen

Field Summary

Fields

Modifier and Type	Field	Description
protected Data	data	Data reference (can be null).
Expr	root	Root expression (can be null).
Expr[]	steps	Path steps.

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

exprType, info

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	Path(InputInfo info, Type type, Expr root, Expr... steps)	Constructor.

Method Summary

Modifier and Type	Method	Description
final boolean	accept(ASTVisitor visitor)	Traverses this expression, notifying the visitor of declared and used variables, and checking the tree for other recursive properties.
final void	checkUp()	Checks if the updating semantics are satisfied.
final Expr	compile(CompileContext cc)	Compiles and optimizes the expression, assigns types and cardinalities.
final VarUsage	count(Var var)	Checks how often a variable or context reference is used in this expression.
final boolean	equals(Object obj)	This function is e.g.
final int	exprSize()	Counts the number of expressions in this expression's sub-tree.
static Expr	get(CompileContext cc, InputInfo ii, Expr root, Expr... steps)	Creates a new, optimized path expression.
static Expr	get(InputInfo ii, Expr root, Expr... steps)	Returns a new path instance.
final boolean	has(Flag... flags)	Indicates if an expression has one of the specified compiler properties.
final Expr	inline(InlineContext ic)	Inlines an expression into this one, replacing all variable or context references.
final boolean	inlineable(InlineContext ic)	Checks if inlining is possible.
final Expr	optimize(CompileContext cc)	Optimizes an already compiled expression without recompiling its sub-expressions.
final ArrayList<PathNode>	pathNodes(Expr rt)	Returns the path nodes that will result from this path.
final void	plan(QueryPlan plan)	Creates a query plan.
void	plan(QueryString qs)	Creates a query string.
boolean	simple()	Checks if this path exclusively contains self, child and attribute steps.
final Expr	simplifyFor(CompileContext.Simplify mode, CompileContext cc)	This function is called at compile time for expressions whose operands might be simplified.

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, value

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

arg, args, atomItem, atomIter, copy, data, data, ddo, funcType, hasFreeVars, indexAccessible, isSimple, markTailCalls, mergeEbv, 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

Field Details

root

public Expr root

Root expression (can be null).

steps

public Expr[] steps

Path steps.

data

protected Data data

Data reference (can be null).

Constructor Details

Path

protected Path(InputInfo info,
 Type type,
 Expr root,
 Expr... steps)

Constructor.

Parameters:

info - input info

type - type

root - root expression (can be null)

steps - steps

Method Details

get

public static Expr get(CompileContext cc,
 InputInfo ii,
 Expr root,
 Expr... steps)
                throws QueryException

Creates a new, optimized path expression.

Parameters:

cc - compilation context

ii - input info

root - root expression (can be temporary Dummy node or null)

steps - steps

Returns:

path instance

Throws:

QueryException - query exception

get

public static Expr get(InputInfo ii,
 Expr root,
 Expr... steps)

Returns a new path instance. A path implementation is chosen that works fastest for the given steps.

Parameters:

ii - input info

root - root expression (can be temporary Dummy node or null)

steps - steps

Returns:

path instance

checkUp

public final 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

compile

public final 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 final 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

simplifyFor

public final Expr simplifyFor(CompileContext.Simplify mode,
 CompileContext cc)
                       throws QueryException

Description copied from class: Expr

This function is called at compile time for expressions whose operands might be simplified.

Overrides:

simplifyFor in class Expr

Parameters:

mode - mode of simplification

cc - compilation context

Returns:

simplified or original expression

Throws:

QueryException - query exception

See Also:

• CompileContext.Simplify

has

public final 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

simple

public boolean simple()

Checks if this path exclusively contains self, child and attribute steps.

Returns:

result of check

pathNodes

public final ArrayList<PathNode> pathNodes(Expr rt)

Returns the path nodes that will result from this path.

Parameters:

rt - root at compile time (can be null)

Returns:

path nodes or null if nodes cannot be evaluated

inlineable

public final 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)
• 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 final 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)

Specified by:

count in class Expr

Parameters:

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

Returns:

number of usages, see VarUsage

inline

public final 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

accept

public final 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. 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

equals

public final 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 final 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