Package org.basex.query.expr.index

Class ValueAccess

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.index.IndexAccess

org.basex.query.expr.index.ValueAccess

public final class ValueAccess
extends IndexAccess

This index class retrieves texts and attribute values from the index.

Author:

BaseX Team 2005-24, BSD License, Christian Gruen

Field Summary

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

exprType, info

Constructor Summary

Constructors

Constructor	Description
ValueAccess(InputInfo info, Expr expr, IndexType type, NameTest test, IndexDb db)	Constructor.
ValueAccess(InputInfo info, TokenSet tokens, IndexType type, NameTest test, IndexDb db)	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.
boolean	equals(Object obj)	This function is e.g. called by: If.optimize(CompileContext), Switch.optimize(CompileContext), Typeswitch.optimize(CompileContext), in order to discard identical expressions.
int	exprSize()	Counts the number of expressions in this expression's subtree.
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	toString(QueryString qs)	Creates a query string.
void	toXml(QueryPlan plan)	Creates a query plan.
Value	value(QueryContext qc)	Evaluates the expression and returns the resulting value.

Methods inherited from class org.basex.query.expr.index.IndexAccess

ddo

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

checkUp, compile

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

adoptType, atomValue, checkAllUp, checkNoneUp, checkNoUp, checkType, checkType, checkUp, copyType, ctxValue, data, info, item, refineType, sc, seqType, size, test, toArray, toArray, toAtomItem, toBin, toBin, toBinOrNull, toBoolean, toBoolean, toBooleanOrFalse, toBytes, toBytes, toDouble, toDouble, toElem, toElem, toEnum, toFloat, toFunction, toLong, toLong, toLong, toMap, toMap, toNode, toNode, toNodeOrNull, toNumber, toNumber, toNumberOrNull, toQNm, toQNmOrNull, toRecord, toString, toString, toStringOrNull, toToken, toToken, toTokenOrNull, toZeroToken

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

arg, args, atomItem, atomIter, funcType, hasFreeVars, indexAccessible, info, isSimple, markTailCalls, mergeEbv, optimize, 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

Constructor Detail

ValueAccess

public ValueAccess(InputInfo info,
                   TokenSet tokens,
                   IndexType type,
                   NameTest test,
                   IndexDb db)

Constructor.

Parameters:

info - input info (can be null)

tokens - tokens

type - index type

test - name test (can be null)

db - index database

ValueAccess

public ValueAccess(InputInfo info,
                   Expr expr,
                   IndexType type,
                   NameTest test,
                   IndexDb db)

Constructor.

Parameters:

info - input info (can be null)

expr - search expression

type - index type

test - test (can be null)

db - index database

Method Detail

iter

public Iter iter(QueryContext qc)
          throws QueryException

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

Throws:

QueryException - query exception

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 IndexAccess

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...). The following tests might reject inlining if the expression depends on the context value:

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

Overrides:

inlineable in class IndexAccess

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, among others, 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 IndexAccess

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 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)

Specified by:

inline in class Expr

Parameters:

ic - inlining context

Returns:

resulting expression if something has changed, null otherwise

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.

Overrides:

accept in class IndexAccess

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 IndexAccess

Returns:

number of expressions

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

Overrides:

equals in class IndexAccess

toXml

public void toXml(QueryPlan plan)

Description copied from class: ExprInfo

Creates a query plan.

Overrides:

toXml in class Simple

Parameters:

plan - expression plan

toString

public void toString(QueryString qs)

Description copied from class: ExprInfo

Creates a query string.

Specified by:

toString in class ExprInfo

Parameters:

qs - query string builder