Package org.basex.query.value.item

Class Item

java.lang.Object

org.basex.query.expr.ExprInfo

org.basex.query.expr.Expr

org.basex.query.value.Value

org.basex.query.value.item.Item

All Implemented Interfaces:

Iterable<Item>

Direct Known Subclasses:

ADateDur, ANode, ANum, AStr, Atm, Bin, Bln, Dummy, Empty, FItem, Jav, QNm

public abstract class Item
extends Value

Abstract super class for all items.

Author:

BaseX Team 2005-21, BSD License, Christian Gruen

Field Summary

Fields

Modifier and Type	Field	Description
static final int	UNDEF	Undefined item.

Fields inherited from class org.basex.query.value.Value

type

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	Item(Type type)	Constructor.

Method Summary

Modifier and Type	Method	Description
Item	atomItem(QueryContext qc, InputInfo ii)	Evaluates the expression and returns the resulting, atomized item, or Empty.VALUE if the expression yields an empty sequence.
long	atomSize()	Computes the number of atomized items.
Value	atomValue(QueryContext qc, InputInfo ii)	Evaluates the expression and returns the atomized items.
boolean	bool(InputInfo ii)	Returns a boolean representation of the value.
void	cache(boolean lazy, InputInfo ii)	Caches lazy values.
boolean	comparable(Item item)	Checks if the items can be compared.
double	dbl(InputInfo ii)	Returns a double representation of the value.
boolean	ddo()	Indicates if this expression returns nodes in document order without duplicates.
BigDecimal	dec(InputInfo ii)	Returns a decimal representation of the value.
String	description()	Returns a string description of the expression.
int	diff(Item item, Collation coll, InputInfo ii)	Returns the difference between the current and the specified item.
Item	ebv(QueryContext qc, InputInfo ii)	Checks if the effective boolean value can be computed for this expression:
abstract boolean	eq(Item item, Collation coll, StaticContext sc, InputInfo ii)	Compares the items for equality.
final boolean	equiv(Item item, Collation coll, InputInfo ii)	Compares the items for equivalence.
float	flt(InputInfo ii)	Returns a float representation of the value.
int	hash(InputInfo ii)	Returns a hash code for this value.
BufferInput	input(InputInfo ii)	Returns an input stream.
boolean	instanceOf(Type tp)	Checks if this item is instance of the specified type.
final Item	item(QueryContext qc, InputInfo ii)	Evaluates the expression and returns the resulting item, or Empty.VALUE if the expression yields an empty sequence.
final Item	itemAt(long pos)	Returns the item at the given position in the value.
BasicIter<Item>	iter()	Returns an iterator.
long	itr(InputInfo ii)	Returns an integer (long) representation of the value.
Item	materialize(QueryContext qc, boolean copy)	Returns a materialized, context-independent version of this item.
final boolean	persistent()	Indicates if this item references a persistent database.
void	plan(QueryPlan plan)	Creates a query plan.
void	refineType(Expr expr)	Refines the expression type.
final Item	reverse(QueryContext qc)	Returns all items of this value in reverse order.
boolean	sameKey(Item item, InputInfo ii)	Compares the items for equality.
double	score()	Returns a score value.
SeqType	seqType()	Returns the static type of the resulting value.
long	size()	Returns the result size, or -1 if the size is unknown.
abstract byte[]	string(InputInfo ii)	Returns a string representation of the value.
Value	subsequence(long start, long length, QueryContext qc)	Returns a subsequence of this value with the given start and length.
Item	test(QueryContext qc, InputInfo ii)	Performs a predicate test and returns the item if the test was successful.
Type.ID	typeId()	Returns a type id.
byte[]	xdmInfo()	Returns data model info.

Methods inherited from class org.basex.query.value.Value

accept, checkUp, compile, copy, count, exprSize, has, inline, inlineable, isEmpty, isItem, iter, iterator, materialize, serialize, serialize, serialize, toJava, value

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

arg, args, atomIter, data, data, equals, funcType, hasFreeVars, indexAccessible, isSimple, markTailCalls, mergeEbv, optimize, simplifyFor, typeCheck, uses, vacuous, visitAll

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

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

UNDEF

public static final int UNDEF

Undefined item.

See Also:

• Constant Field Values

Constructor Details

Item

protected Item(Type type)

Constructor.

Parameters:

type - item type

Method Details

iter

public BasicIter<Item> iter()

Description copied from class: Value

Returns an iterator.

Specified by:

iter in class Value

Returns:

iterator

item

public final Item item(QueryContext qc,
 InputInfo ii)

Description copied from class: Expr

Evaluates the expression and returns the resulting item, or Empty.VALUE if the expression yields an empty sequence. If this method is not implemented, Expr.value(QueryContext) must be implemented instead.

Specified by:

item in class Expr

Parameters:

qc - query context

ii - input info (only required by Seq instances, which have no input info)

Returns:

item or Empty.VALUE

itemAt

public final Item itemAt(long pos)

Description copied from class: Value

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

Specified by:

itemAt in class Value

Parameters:

pos - position

Returns:

item

reverse

public final Item reverse(QueryContext qc)

Description copied from class: Value

Returns all items of this value in reverse order.

Specified by:

reverse in class Value

Parameters:

qc - query context

Returns:

items in reverse order

ebv

public Item ebv(QueryContext qc,
 InputInfo ii)

Description copied from class: Expr

Checks if the effective boolean value can be computed for this expression:

• If it yields an empty sequence, Bln.FALSE will be returned.
• If it yields a single item, this item will be returned.
• If it yields nodes, the first node will be returned.
• Otherwise, an error will be raised.

A single numeric item may later be evaluated as positional predicate.

Specified by:

ebv in class Expr

Parameters:

qc - query context

ii - input info (required for Seq instances, which have no input info)

Returns:

item

test

public Item test(QueryContext qc,
 InputInfo ii)
          throws QueryException

Description copied from class: Expr

Performs a predicate test and returns the item if the test was successful. The returned item is required for full-text scoring.

Specified by:

test in class Expr

Parameters:

qc - query context

ii - input info (required for Seq instances, which have no input info)

Returns:

item or null

Throws:

QueryException - query exception

string

public abstract byte[] string(InputInfo ii)
                       throws QueryException

Returns a string representation of the value.

Parameters:

ii - input info (can be null)

Returns:

string value

Throws:

QueryException - if the item cannot be atomized (caused by function or streaming items)

bool

public boolean bool(InputInfo ii)
             throws QueryException

Returns a boolean representation of the value.

Parameters:

ii - input info (can be null)

Returns:

boolean value

Throws:

QueryException - query exception

dec

public BigDecimal dec(InputInfo ii)
               throws QueryException

Returns a decimal representation of the value.

Parameters:

ii - input info (can be null)

Returns:

decimal value

Throws:

QueryException - query exception

itr

public long itr(InputInfo ii)
         throws QueryException

Returns an integer (long) representation of the value.

Parameters:

ii - input info (can be null)

Returns:

long value

Throws:

QueryException - query exception

flt

public float flt(InputInfo ii)
          throws QueryException

Returns a float representation of the value.

Parameters:

ii - input info (can be null)

Returns:

float value

Throws:

QueryException - query exception

dbl

public double dbl(InputInfo ii)
           throws QueryException

Returns a double representation of the value.

Parameters:

ii - input info (can be null)

Returns:

double value

Throws:

QueryException - query exception

instanceOf

public boolean instanceOf(Type tp)

Checks if this item is instance of the specified type. Overwritten by XQMap and XQArray.

Parameters:

tp - type

Returns:

result of check

comparable

public boolean comparable(Item item)

Checks if the items can be compared.

Parameters:

item - item to be compared

Returns:

result of check

eq

public abstract boolean eq(Item item,
 Collation coll,
 StaticContext sc,
 InputInfo ii)
                    throws QueryException

Compares the items for equality.

Parameters:

item - item to be compared

coll - collation (can be null)

sc - static context; required for comparing items of type xs:QName (can be null)

ii - input info (can be null)

Returns:

result of check

Throws:

QueryException - query exception

equiv

public final boolean equiv(Item item,
 Collation coll,
 InputInfo ii)
                    throws QueryException

Compares the items for equivalence. As item is equivalent to another if:

• both numeric values are NaN, or
• if the items have comparable types and are equal

Parameters:

item - item to be compared

coll - collation (can be null)

ii - input info (can be null)

Returns:

result of check

Throws:

QueryException - query exception

sameKey

public boolean sameKey(Item item,
 InputInfo ii)
                throws QueryException

Compares the items for equality.

Parameters:

item - item to be compared

ii - input info (can be null)

Returns:

result of check

Throws:

QueryException - query exception

diff

public int diff(Item item,
 Collation coll,
 InputInfo ii)
         throws QueryException

Returns the difference between the current and the specified item. This function is overwritten by the corresponding implementations.

Parameters:

item - item to be compared

coll - collation (can be null)

ii - input info (can be null)

Returns:

difference

Throws:

QueryException - query exception

input

public BufferInput input(InputInfo ii)
                  throws QueryException

Returns an input stream.

Parameters:

ii - input info (can be null)

Returns:

input stream

Throws:

QueryException - query exception

subsequence

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

Description copied from class: Value

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

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

Specified by:

subsequence in class Value

Parameters:

start - starting position

length - number of items

qc - query context

Returns:

sub sequence

cache

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

Caches lazy values. Overwritten by Lazy, XQMap and XQArray.

Specified by:

cache in class Value

Parameters:

lazy - lazy caching

ii - input info

Throws:

QueryException - query exception

atomValue

public Value atomValue(QueryContext qc,
 InputInfo ii)
                throws QueryException

Evaluates the expression and returns the atomized items. Overwritten by XQArray, FuncItem and ANode.

Specified by:

atomValue in class Expr

Parameters:

qc - query context

ii - input info (only required by Seq instances, which have no input info)

Returns:

atomized item

Throws:

QueryException - query exception

atomItem

public Item atomItem(QueryContext qc,
 InputInfo ii)
              throws QueryException

Evaluates the expression and returns the resulting, atomized item, or Empty.VALUE if the expression yields an empty sequence. Overwritten by XQArray, FuncItem and ANode.

Overrides:

atomItem in class Expr

Parameters:

qc - query context

ii - input info (only required by Seq instances, which have no input info)

Returns:

item or Empty.VALUE

Throws:

QueryException - query exception

atomSize

public long atomSize()

Computes the number of atomized items. Overwritten by XQArray.

Specified by:

atomSize in class Value

Returns:

atomized item

materialize

public Item materialize(QueryContext qc,
 boolean copy)

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

Parameters:

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

copy - create full copy

Returns:

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

seqType

public SeqType seqType()

Description copied from class: Expr

Returns the static type of the resulting value.

Specified by:

seqType in class Expr

Returns:

result of check

size

public long size()

Description copied from class: Expr

Returns the result size, or -1 if the size is unknown.

Specified by:

size in class Expr

Returns:

result of check

refineType

public void refineType(Expr expr)

Description copied from class: Expr

Refines the expression type.

Specified by:

refineType in class Expr

Parameters:

expr - original expression

ddo

public boolean ddo()

Description copied from class: Expr

Indicates if this expression returns nodes in document order without duplicates.

Overrides:

ddo in class Expr

Returns:

result of check

persistent

public final boolean persistent()

Indicates if this item references a persistent database.

Returns:

result of check

score

public double score()

Returns a score value. Overwritten by FTNode.

Returns:

score value

hash

public int hash(InputInfo ii)
         throws QueryException

Description copied from class: Value

Returns a hash code for this value.

Specified by:

hash in class Value

Parameters:

ii - input info

Returns:

hash code

Throws:

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

xdmInfo

public byte[] xdmInfo()

Returns data model info. Overwritten by QNm, DBNode, FTxt and FDoc.

Returns:

type string

typeId

public Type.ID typeId()

Returns a type id. Overwritten by DBNode and FDoc.

Returns:

type string

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