Package org.basex.query.expr.path

Class Step

java.lang.Object

org.basex.query.expr.ExprInfo

org.basex.query.expr.Expr

org.basex.query.expr.ParseExpr

org.basex.query.expr.Arr

org.basex.query.expr.Preds

org.basex.query.expr.path.Step

Direct Known Subclasses:

CachedStep, IterPosStep, IterStep

public abstract class Step
extends Preds

Abstract axis step expression.

Author:

BaseX Team 2005-22, BSD License, Christian Gruen

Field Summary

Fields

Modifier and Type	Field	Description
Axis	axis	Axis.
Test	test	Kind test.

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

exprs

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

exprType, info

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.
abstract Step	copy(CompileContext cc, IntObjMap<Var> vm)	Copies an expression.
boolean	equals(Object obj)	This function is e.g.
int	exprSize()	Counts the number of expressions in this expression's subtree.
static Expr	get(CompileContext cc, Expr root, InputInfo ii, Expr... preds)	Returns a new optimized self::node() step.
static Expr	get(CompileContext cc, Expr root, InputInfo ii, Axis axis, Test test, Expr... preds)	Returns a new optimized step.
static Expr	get(CompileContext cc, Expr root, InputInfo ii, Test test, Expr... preds)	Returns a new optimized self step.
static Step	get(InputInfo ii, Axis axis, Test test, Expr... preds)	Returns a new step.
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.
static SeqType	seqType(Axis axis, Test test, Expr... preds)	Determines the sequence type of the step.
void	toString(QueryString qs)	Creates a query string.
void	toXml(QueryPlan plan)	Creates a query plan.
protected Expr	type(Expr expr)	Assigns the expression type.
Value	value(QueryContext qc)	Evaluates the expression and returns the resulting value.

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

compile, flattenEbv, inlineable, match, mayBePositional, numeric, simplify

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

allAreValues, args, checkUp, copyAll, count, flatten, has, mayBePositional, removeEmpty, simplifyAll

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

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

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

arg, atomItem, atomIter, ddo, funcType, hasFreeVars, indexAccessible, isSimple, markTailCalls, mergeEbv, optimizePos, simplify, 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

Field Detail

test

public Test test

Kind test.

axis

public Axis axis

Axis.

Method Detail

get

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

Returns a new optimized self::node() step.

Parameters:

cc - compilation context

root - root context expression; if null, the current context will be used

ii - input info

preds - predicates

Returns:

step

Throws:

QueryException - query exception

get

public static Expr get(CompileContext cc,
                       Expr root,
                       InputInfo ii,
                       Test test,
                       Expr... preds)
                throws QueryException

Returns a new optimized self step.

Parameters:

cc - compilation context

root - root context expression; if null, the current context will be used

ii - input info

test - test

preds - predicates

Returns:

step

Throws:

QueryException - query exception

get

public static Expr get(CompileContext cc,
                       Expr root,
                       InputInfo ii,
                       Axis axis,
                       Test test,
                       Expr... preds)
                throws QueryException

Returns a new optimized step.

Parameters:

cc - compilation context

root - root context expression; if null, the current context will be used

ii - input info

axis - axis

test - node test

preds - predicates

Returns:

step

Throws:

QueryException - query exception

get

public static Step get(InputInfo ii,
                       Axis axis,
                       Test test,
                       Expr... preds)

Returns a new step.

Parameters:

ii - input info

axis - axis

test - node test

preds - predicates

Returns:

step

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

type

protected final Expr type(Expr expr)

Description copied from class: Preds

Assigns the expression type.

Specified by:

type in class Preds

Parameters:

expr - root expression (can be null)

Returns:

actual root expression (can be null)

seqType

public static SeqType seqType(Axis axis,
                              Test test,
                              Expr... preds)

Determines the sequence type of the step.

Parameters:

axis - axis

test - test

preds - predicates

Returns:

sequence type

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 these 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)

Overrides:

inline in class Arr

Parameters:

ic - inlining context

Returns:

resulting expression if something has changed, null otherwise

Throws:

QueryException - query exception

value

public final 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

copy

public abstract Step 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 Arr

Parameters:

visitor - visitor

Returns:

if the walk should be continued

exprSize

public int exprSize()

Description copied from class: Expr

Counts the number of expressions in this expression's subtree. 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.

Overrides:

exprSize in class Arr

Returns:

number of expressions

equals

public boolean equals(Object obj)

Description copied from class: Arr

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), in order to compare the start and end value.
• PathCache, in order to find identical root values at runtime.

Must be overwritten by implementing class.

Overrides:

equals in class Arr

toXml

public final void toXml(QueryPlan plan)

Description copied from class: ExprInfo

Creates a query plan.

Overrides:

toXml in class Arr

Parameters:

plan - expression plan

toString

public void toString(QueryString qs)

Description copied from class: ExprInfo

Creates a query string.

Overrides:

toString in class Preds

Parameters:

qs - query string builder