Package org.basex.query.value.item

Class Dummy

java.lang.Object

org.basex.query.expr.ExprInfo

org.basex.query.expr.Expr

org.basex.query.value.Value

org.basex.query.value.item.Dummy

All Implemented Interfaces:

Iterable<Item>

public final class Dummy
extends Value

Dummy item (only used at compile time).

Author:

BaseX Team 2005-24, BSD License, Christian Gruen

Field Summary

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

type

Constructor Summary

Constructors

Constructor	Description
Dummy(Expr expr, boolean item)	Constructor.

Method Summary

Modifier and Type	Method	Description
Value	atomValue(QueryContext qc, InputInfo ii)	Evaluates the expression and returns the atomized items.
void	cache(boolean lazy, InputInfo ii)	Caches data of lazy items (i.e., those implementing the Lazy interface).
Data	data()	Returns the data reference bound to 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.
Item	item(QueryContext qc, InputInfo ii)	Evaluates the expression and returns the resulting item, or Empty.VALUE if the expression yields an empty sequence.
Item	itemAt(long pos)	Returns the item at the given position in the value.
BasicIter<Item>	iter()	Returns an iterator.
Value	materialize(Predicate<Data> test, InputInfo ii, QueryContext qc)	Returns a materialized version of this value without dependencies to persistent data.
boolean	materialized(Predicate<Data> test, InputInfo ii)	Checks if this value is materialized, i.e., contains no persistent database nodes or function items.
void	refineType(Expr ex)	Refines the expression type.
Value	reverse(QueryContext qc)	Returns all items of this value in reverse order.
boolean	sameType()	Checks if all items of the sequence are of the same type.
SeqType	seqType()	Returns the static type of the resulting value.
long	size()	Returns the result size, or -1 if the size is unknown.
Value	subsequence(long start, long length, QueryContext qc)	Returns a subsequence of this value with the given start and length.
boolean	test(QueryContext qc, InputInfo ii, long pos)	Computes the effective boolean value for this expression.
String	toJava()	Returns a Java representation of the value.
void	toString(QueryString qs)	Creates a query string.
void	toXml(QueryPlan plan)	Creates a query plan.

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

accept, checkUp, compactify, compile, copy, count, exprSize, get, has, inline, inlineable, isEmpty, isItem, iter, iterator, refineType, refineType, serialize, serialize, serialize, value, write

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

arg, args, atomItem, atomIter, ddo, 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, info, 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

Constructor Detail

Dummy

public Dummy(Expr expr,
             boolean item)

Constructor.

Parameters:

expr - input expression

item - focus single item

Method Detail

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

data

public Data data()

Description copied from class: Expr

Returns the data reference bound to this expression. This method is currently overwritten by DBNode, DBNodeSeq, AxisPath and VarRef.

Overrides:

data in class Expr

Returns:

data reference (can be null)

toJava

public String toJava()

Description copied from class: Value

Returns a Java representation of the value.

Specified by:

toJava in class Value

Returns:

Java object

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.

Specified by:

equals in class Expr

toXml

public void toXml(QueryPlan plan)

Description copied from class: ExprInfo

Creates a query plan.

Specified by:

toXml in class ExprInfo

Parameters:

plan - expression plan

iter

public BasicIter<Item> iter()

Description copied from class: Value

Returns an iterator.

Specified by:

iter in class Value

Returns:

iterator

materialize

public Value materialize(Predicate<Data> test,
                         InputInfo ii,
                         QueryContext qc)
                  throws QueryException

Description copied from class: Value

Returns a materialized version of this value without dependencies to persistent data. Raises an error if the value contains function items.

Specified by:

materialize in class Value

Parameters:

test - test to check if a node can be adopted unchanged

ii - input info (can be null)

qc - query context

Returns:

materialized value

Throws:

QueryException - query exception

materialized

public boolean materialized(Predicate<Data> test,
                            InputInfo ii)
                     throws QueryException

Description copied from class: Value

Checks if this value is materialized, i.e., contains no persistent database nodes or function items.

Specified by:

materialized in class Value

Parameters:

test - test to check if a node can be adopted unchanged

ii - input info (can be null)

Returns:

result of check

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

Description copied from class: Value

Caches data of lazy items (i.e., those implementing the Lazy interface). By calling this method, the streaming feature of lazy items will be disabled.

Specified by:

cache in class Value

Parameters:

lazy - if false, cache immediately. if true, caching is deferred until the data is actually requested

ii - input info (can be null)

Throws:

QueryException - query exception

sameType

public boolean sameType()

Description copied from class: Value

Checks if all items of the sequence are of the same type.

Specified by:

sameType in class Value

Returns:

result of check

itemAt

public 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 Value 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

item

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

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 (can be null); required for those Value instances that have no input info)

Returns:

item or Empty.VALUE

Throws:

QueryException - query exception

atomValue

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

Description copied from class: Expr

Evaluates the expression and returns the atomized items.

Specified by:

atomValue in class Expr

Parameters:

qc - query context

ii - input info (can be null); required for those Value instances that have no input info)

Returns:

atomized item

Throws:

QueryException - query exception

test

public boolean test(QueryContext qc,
                    InputInfo ii,
                    long pos)
             throws QueryException

Description copied from class: Expr

Computes the effective boolean value for this expression.

Specified by:

test in class Expr

Parameters:

qc - query context

ii - input info (can be null); required for those Value instances that have no input info)

pos - position of context item (if 0, perform EBV test)

Returns:

item

Throws:

QueryException - query exception

refineType

public void refineType(Expr ex)

Description copied from class: Expr

Refines the expression type.

Specified by:

refineType in class Expr

Parameters:

ex - original expression

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