org.basex.query.expr
Class CmpG

java.lang.Object
  org.basex.query.ExprInfo
      org.basex.query.expr.Expr
          org.basex.query.expr.Arr
              org.basex.query.expr.CmpG

public final class CmpG
extends Arr

General comparison.

Author:

Workgroup DBIS, University of Konstanz 2005-10, ISC License, Christian Gruen

Nested Class Summary

static class

CmpG.Comp Comparators.

Nested classes/interfaces inherited from class org.basex.query.expr.Expr

Expr.Use

Field Summary

CmpG.Comp

cmp Comparator.

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

expr

Constructor Summary

CmpG(Expr e1, Expr e2, CmpG.Comp c)
Constructor.

Method Summary

Bln	atomic(QueryContext ctx) Evaluates the expression and returns the resulting item or a null reference.
String	color() Returns a color string for the expression.
Expr	comp(QueryContext ctx) Optimizes and compiles the expression.
boolean	indexAccessible(IndexContext ic) Checks if an index can be used for query evaluation.
Expr	indexEquivalent(IndexContext ic) Returns an equivalent expression which accesses an index structure.
static Step	indexStep(Expr expr) Returns the indexable index step or null.
String	info() Returns a string description of the expression.
void	plan(Serializer ser) Recursively sends the abstract syntax of this expression to the specified serializer.
Return	returned(QueryContext ctx) Indicates the return type of an expression.
String	toString()

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

duplicates, removable, remove, uses

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

addText, checkCtx, checkDbl, checkItr, e, ebv, i, iter, sameAs, size, test, v

Methods inherited from class org.basex.query.ExprInfo

name

Methods inherited from class java.lang.Object

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

Field Detail

cmp

public CmpG.Comp cmp

Comparator.

Constructor Detail

CmpG

public CmpG(Expr e1,
            Expr e2,
            CmpG.Comp c)

Constructor.

Parameters:

e1 - first expression

e2 - second expression

c - comparator

Method Detail

comp

public Expr comp(QueryContext ctx)
          throws QueryException

Description copied from class: Expr

Optimizes and compiles the expression.

Overrides:

comp in class Arr

Parameters:

ctx - query context

Returns:

optimized Expression

Throws:

QueryException - query exception

atomic

public Bln 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

indexAccessible

public boolean indexAccessible(IndexContext ic)
                        throws QueryException

Description copied from class: Expr

Checks if an index can be used for query evaluation.

Overrides:

indexAccessible in class Expr

Parameters:

ic - index context

Returns:

true if an index can be used

Throws:

QueryException - query exception

indexEquivalent

public Expr indexEquivalent(IndexContext ic)

Description copied from class: Expr

Returns an equivalent expression which accesses an index structure. Must be called if Expr.indexAccessible(org.basex.query.IndexContext) is implemented for an expression.

Overrides:

indexEquivalent in class Arr

Parameters:

ic - index context

Returns:

Equivalent index-expression or null

indexStep

public static Step indexStep(Expr expr)

Returns the indexable index step or null.

Parameters:

expr - expression arguments

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

info

public String info()

Description copied from class: ExprInfo

Returns a string description of the expression. Contrary to the ExprInfo.toString() method, arguments are not included in the output.

Overrides:

info in class ExprInfo

Returns:

result of check

color

public String color()

Description copied from class: ExprInfo

Returns a color string for the expression.

Overrides:

color in class ExprInfo

Returns:

color

plan

public void plan(Serializer ser)
          throws IOException

Description copied from class: ExprInfo

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

Overrides:

plan in class Arr

Parameters:

ser - serializer

Throws:

IOException - I/O exception

toString

public String toString()

Specified by:

toString in class ExprInfo