org.basex.query.item
Class Item

java.lang.Object
  org.basex.query.ExprInfo
      org.basex.query.expr.Expr
          org.basex.query.item.Item

Direct Known Subclasses:

B64, Bln, Date, Dbl, Dec, Dur, Flt, Hex, Itr, Jav, Nod, QNm, Seq, Str

public abstract class Item
extends Expr

Abstract item.

Author:

Workgroup DBIS, University of Konstanz 2005-09, ISC License, Christian Gruen

Field Summary

Type	type Data type.

Method Summary

Item	atomic(QueryContext ctx) Evaluates the expression and returns the resulting item or a null reference.
boolean	bool() Returns a boolean representation of the item.
void	castErr(java.lang.Object val) Throws a cast error.
Expr	comp(QueryContext ctx) Optimizes and compiles the expression.
boolean	d() Checks if this is a duration.
double	dbl() Returns a double representation of the item.
java.math.BigDecimal	dec() Returns a decimal representation of the item.
int	diff(Item it) Returns the difference between the current and the specified item.
boolean	duplicates(QueryContext ctx) Returns true if the expression might yield duplicates and unsorted results.
Item	ebv(QueryContext ctx) Checks if the iterator can be dissolved into an effective boolean value.
abstract boolean	eq(Item it) Checks the items for equality.
float	flt() Returns a float representation of the item.
int	hash() Returns a hash code.
boolean	i() Checks if this is an item.
Iter	iter() Returns an item iterator.
Iter	iter(QueryContext ctx) Evaluates the expression and returns an iterator on the resulting items.
long	itr() Returns an integer (long) representation of the item.
java.lang.Object	java() Returns a Java object.
boolean	n() Checks if this is a numeric item.
byte[]	name() Returns the simplified class name (for debugging).
boolean	node() Checks if this is a node.
void	plan(Serializer ser) Recursively sends the abstract syntax of this expression to the specified serializer.
boolean	removable(Var v, QueryContext ctx) Checks if the specified variable is removable.
Return	returned(QueryContext ctx) Indicates the return type of an expression.
boolean	s() Checks if this is a string item.
double	score() Returns a score value.
void	score(double s) Sets a new score value.
void	serialize(Serializer ser) Serializes the item.
byte[]	str() Returns an atomized string.
Item	test(QueryContext ctx) Performs a predicate test and returns the item if test was successful.
java.lang.String	toString()
boolean	u() Checks if this is an untyped item.
boolean	uses(Expr.Use use, QueryContext ctx) Indicates if an expression uses the specified type.

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

addText, checkCtx, checkDbl, checkItr, e, indexAccessible, indexEquivalent, remove, sameAs, size

Methods inherited from class org.basex.query.ExprInfo

color, info

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

type

public Type type

Data type.

Method Detail

comp

public Expr comp(QueryContext ctx)

Description copied from class: Expr

Optimizes and compiles the expression.

Specified by:

comp in class Expr

Parameters:

ctx - query context

Returns:

optimized Expression

iter

public Iter iter(QueryContext ctx)

Description copied from class: Expr

Evaluates the expression and returns an iterator on the resulting items. If this method is not overwritten, Expr.atomic(org.basex.query.QueryContext) must be implemented.

Overrides:

iter in class Expr

Parameters:

ctx - query context

Returns:

resulting item

iter

public Iter iter()

Returns an item iterator.

Returns:

iterator

atomic

public Item atomic(QueryContext ctx)
            throws QueryException

Description copied from class: Expr

Evaluates the expression and returns the resulting item or a null reference. If this method is not overwritten, Expr.iter(org.basex.query.QueryContext) must be implemented.

Overrides:

atomic in class Expr

Parameters:

ctx - query context

Returns:

iterator

Throws:

QueryException - query exception

ebv

public Item ebv(QueryContext ctx)
         throws QueryException

Description copied from class: Expr

Checks if the iterator can be dissolved into an effective boolean value. If not, returns an error. If yes, returns the first value - which can be also be e.g. an integer, which is later evaluated as position predicate.

Overrides:

ebv in class Expr

Parameters:

ctx - query context

Returns:

item

Throws:

QueryException - query exception

test

public Item test(QueryContext ctx)
          throws QueryException

Description copied from class: Expr

Performs a predicate test and returns the item if test was successful.

Overrides:

test in class Expr

Parameters:

ctx - query context

Returns:

item

Throws:

QueryException - evaluation exception

i

public boolean i()

Description copied from class: Expr

Checks if this is an item.

Overrides:

i in class Expr

Returns:

result of check

n

public final boolean n()

Checks if this is a numeric item.

Returns:

result of check

u

public final boolean u()

Checks if this is an untyped item.

Returns:

result of check

s

public final boolean s()

Checks if this is a string item.

Returns:

result of check

d

public final boolean d()

Checks if this is a duration.

Returns:

result of check

node

public final boolean node()

Checks if this is a node.

Returns:

result of check

str

public byte[] str()

Returns an atomized string.

Returns:

string representation

hash

public int hash()

Returns a hash code.

Returns:

hash code

java

public java.lang.Object java()

Returns a Java object.

Returns:

string representation

bool

public boolean bool()
             throws QueryException

Returns a boolean representation of the item.

Returns:

boolean value

Throws:

QueryException - evaluation exception

dec

public java.math.BigDecimal dec()
                         throws QueryException

Returns a decimal representation of the item.

Returns:

decimal value

Throws:

QueryException - evaluation exception

itr

public long itr()
         throws QueryException

Returns an integer (long) representation of the item.

Returns:

long value

Throws:

QueryException - evaluation exception

flt

public float flt()
          throws QueryException

Returns a float representation of the item.

Returns:

float value

Throws:

QueryException - evaluation exception

dbl

public double dbl()
           throws QueryException

Returns a double representation of the item.

Returns:

double value

Throws:

QueryException - evaluation exception

eq

public abstract boolean eq(Item it)
                    throws QueryException

Checks the items for equality.

Parameters:

it - item to be compared.

Returns:

result of check

Throws:

QueryException - evaluation exception

diff

public int diff(Item it)
         throws QueryException

Returns the difference between the current and the specified item.

Parameters:

it - item to be compared.

Returns:

difference

Throws:

QueryException - evaluation exception

score

public double score()

Returns a score value.

Returns:

score value

score

public final void score(double s)

Sets a new score value.

Parameters:

s - score value

castErr

public final void castErr(java.lang.Object val)
                   throws QueryException

Throws a cast error.

Parameters:

val - cast value

Throws:

QueryException - evaluation exception

serialize

public void serialize(Serializer ser)
               throws java.io.IOException

Serializes the item.

Parameters:

ser - serializer

Throws:

java.io.IOException - exception

uses

public boolean uses(Expr.Use use,
                    QueryContext ctx)

Description copied from class: Expr

Indicates if an expression uses the specified type. Called by the compiler to perform certain optimizations. true is returned by default and thus assumed as "worst-case".

Overrides:

uses in class Expr

Parameters:

use - use type to be checked

ctx - query context

Returns:

result of check

removable

public boolean removable(Var v,
                         QueryContext ctx)

Description copied from class: Expr

Checks if the specified variable is removable.

Overrides:

removable in class Expr

Parameters:

v - variable to be removed

ctx - query context

Returns:

result of check

returned

public Return returned(QueryContext ctx)

Description copied from class: Expr

Indicates the return type of an expression. Called by the compiler to check if expressions can be reformulated. null is returned by default.

Overrides:

returned in class Expr

Parameters:

ctx - query context

Returns:

result of check

duplicates

public boolean duplicates(QueryContext ctx)

Description copied from class: Expr

Returns true if the expression might yield duplicates and unsorted results.

Overrides:

duplicates in class Expr

Parameters:

ctx - query context

Returns:

result of check

name

public final byte[] name()

Description copied from class: ExprInfo

Returns the simplified class name (for debugging).

Overrides:

name in class ExprInfo

Returns:

class name

plan

public void plan(Serializer ser)
          throws java.io.IOException

Description copied from class: ExprInfo

Recursively sends the abstract syntax of this expression to the specified serializer.

Specified by:

plan in class ExprInfo

Parameters:

ser - serializer

Throws:

java.io.IOException - exception

toString

public java.lang.String toString()

Specified by:

toString in class ExprInfo