Package org.basex.query.value

Class Value

java.lang.Object

org.basex.query.expr.ExprInfo

org.basex.query.expr.Expr

org.basex.query.value.Value

All Implemented Interfaces:

Iterable<Item>

Direct Known Subclasses:

Item, Seq

public abstract class Value
extends Expr
implements Iterable<Item>

Abstract value. This class also implements the Iterable interface, which is why all of its values can also be retrieved via enhanced for(for-each) loops. The default iter() method will provide better performance.

Author:

BaseX Team 2005-21, BSD License, Christian Gruen

Field Summary

Fields

Modifier and Type	Field	Description
Type	type	Item type.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	Value(Type type)	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.
abstract long	atomSize()	Computes the number of atomized items.
abstract void	cache(boolean lazy, InputInfo ii)	Caches lazy values.
final void	checkUp()	Checks if the updating semantics are satisfied.
final Value	compile(CompileContext cc)	Compiles and optimizes the expression, assigns types and cardinalities.
Value	copy(CompileContext cc, IntObjMap<Var> vm)	Copies an expression.
final VarUsage	count(Var var)	Checks how often a variable or context reference is used in this expression.
final int	exprSize()	Counts the number of expressions in this expression's sub-tree.
final boolean	has(Flag... flags)	Indicates if an expression has one of the specified compiler properties.
abstract int	hash(InputInfo ii)	Returns a hash code for this value.
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 boolean	isEmpty()	Tests if this is an empty sequence.
final boolean	isItem()	Tests if this is an item.
abstract Item	itemAt(long pos)	Returns the item at the given position in the value.
abstract BasicIter<Item>	iter()	Returns an iterator.
final BasicIter<Item>	iter(QueryContext qc)	Evaluates the expression and returns an iterator on the resulting items.
Iterator<Item>	iterator()
Value	materialize(QueryContext qc, QueryError error, InputInfo info)	Returns a materialized, context-independent version of this value.
abstract Value	reverse(QueryContext qc)	Returns all items of this value in reverse order.
final ArrayOutput	serialize()	Serializes the value, using the standard XML serializer, and returns the cached result.
final void	serialize(Serializer ser)	Serializes the value with the specified serializer.
final ArrayOutput	serialize(SerializerOptions options)	Serializes the value with the specified serialization parameters and returns the cached result.
abstract Value	subsequence(long start, long length, QueryContext qc)	Returns a subsequence of this value with the given start and length.
abstract Object	toJava()	Returns a Java representation of the value.
final Value	value(QueryContext qc)	Evaluates the expression and returns the resulting value.

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

arg, args, atomItem, atomIter, atomValue, data, data, ddo, ebv, equals, funcType, hasFreeVars, indexAccessible, isSimple, item, markTailCalls, mergeEbv, optimize, refineType, seqType, simplifyFor, size, test, typeCheck, uses, vacuous, visitAll

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

description, plan, plan, toErrorString, toString

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Field Details

type

public Type type

Item type.

Constructor Details

Value

protected Value(Type type)

Constructor.

Parameters:

type - item type

Method Details

checkUp

public final void checkUp()

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

compile

public final Value compile(CompileContext cc)

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

iter

public final BasicIter<Item> 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.

Specified by:

iter in class Expr

Parameters:

qc - query context

Returns:

iterator

iterator

public Iterator<Item> iterator()

Specified by:

iterator in interface Iterable<Item>

iter

public abstract BasicIter<Item> iter()

Returns an iterator.

Returns:

iterator

value

public final Value value(QueryContext qc)

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.

Specified by:

value in class Expr

Parameters:

qc - query context

Returns:

value

materialize

public Value materialize(QueryContext qc,
 QueryError error,
 InputInfo info)
                  throws QueryException

Returns a materialized, context-independent version of this value.

Parameters:

qc - query context (if null, process cannot be interrupted)

error - query error

info - input info

Returns:

item copy, or null) if the value cannot be materialized

Throws:

QueryException - query exception

isEmpty

public final boolean isEmpty()

Tests if this is an empty sequence.

Returns:

result of check

isItem

public final boolean isItem()

Tests if this is an item.

Returns:

result of check

subsequence

public abstract Value subsequence(long start,
 long length,
 QueryContext qc)

Returns a subsequence of this value with the given start and length. The following properties must hold:

• start >= 0,
• length >= 0,
• length <= size() - start

Parameters:

start - starting position

length - number of items

qc - query context

Returns:

sub sequence

cache

public abstract void cache(boolean lazy,
 InputInfo ii)
                    throws QueryException

Caches lazy values.

Parameters:

lazy - lazy caching

ii - input info

Throws:

QueryException - query exception

atomSize

public abstract long atomSize()

Computes the number of atomized items.

Returns:

atomized item

toJava

public abstract Object toJava()
                       throws QueryException

Returns a Java representation of the value.

Returns:

Java object

Throws:

QueryException - query exception

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

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)
• 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 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)

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

copy

public Value 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

hash

public abstract int hash(InputInfo ii)
                  throws QueryException

Returns a hash code for this value.

Parameters:

ii - input info

Returns:

hash code

Throws:

QueryException - if atomization can't be applied (e.g. function item)

serialize

public final ArrayOutput serialize()
                            throws QueryIOException

Serializes the value, using the standard XML serializer, and returns the cached result.

Returns:

serialized value

Throws:

QueryIOException - query I/O exception

serialize

public final ArrayOutput serialize(SerializerOptions options)
                            throws QueryIOException

Serializes the value with the specified serialization parameters and returns the cached result.

Parameters:

options - serialization parameters (may be null)

Returns:

serialized value

Throws:

QueryIOException - query I/O exception

serialize

public final void serialize(Serializer ser)
                     throws IOException

Serializes the value with the specified serializer.

Parameters:

ser - serializer

Throws:

IOException - I/O exception

itemAt

public abstract Item itemAt(long pos)

Returns the item at the given position in the value. The specified value must be lie within the valid bounds.

Parameters:

pos - position

Returns:

item

reverse

public abstract Value reverse(QueryContext qc)

Returns all items of this value in reverse order.

Parameters:

qc - query context

Returns:

items in reverse order

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

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