org.basex.query.ft

Class FTWeight

java.lang.Object

org.basex.data.ExprInfo

org.basex.query.expr.Expr

org.basex.query.expr.ParseExpr

org.basex.query.ft.FTExpr

org.basex.query.ft.FTWeight

public final class FTWeight
extends FTExpr

FTOptions expression.

Author:

BaseX Team 2005-12, BSD License, Christian Gruen

Nested Class Summary

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

Expr.Use

Field Summary

Fields inherited from class org.basex.query.ft.FTExpr

expr

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

input, size, type

Constructor Summary

Constructors

Constructor and Description
FTWeight(InputInfo ii, FTExpr e, Expr w) Constructor.

Method Summary

Methods

Modifier and Type	Method and Description
FTExpr	comp(QueryContext ctx) Compiles and optimizes the expression, assigns data types and cardinalities.
int	count(Var v) Counts how often the specified variable is used by an expression.
boolean	indexAccessible(IndexContext ic) Checks if an expression can be rewritten to an index access.
FTNode	item(QueryContext ctx, InputInfo ii) This method is called by the sequential full-text evaluation.
FTIter	iter(QueryContext ctx) This method is called by the index-based full-text evaluation.
void	plan(Serializer ser) Serializes the expression tree.
boolean	removable(Var v) Checks if the specified variable is replaceable by a context item.
FTExpr	remove(Var v) Substitutes all VarRef expressions for the given variable by a Context reference.
java.lang.String	toString()
boolean	uses(Expr.Use u) Indicates if an expression uses the specified type or operation.

Methods inherited from class org.basex.query.ft.FTExpr

indexEquivalent

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

checkBln, checkColl, checkCreate, checkCtx, checkDbl, checkDBNode, checkEStr, checkEStr, checkIO, checkItem, checkItr, checkItr, checkMap, checkNode, checkNoEmpty, checkStr, checkType, checkUp, checkUp, checkWrite, compBln, ebv, optPre, preEval, size, test, type, value

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

addText, compEbv, hasFreeVars, isEmpty, isFunction, isItem, isVacuous, isValue, iterable, markTailCalls, sameAs

Methods inherited from class org.basex.data.ExprInfo

description, info

Methods inherited from class java.lang.Object

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

Constructor Detail

FTWeight

public FTWeight(InputInfo ii,
        FTExpr e,
        Expr w)

Constructor.

Parameters:

ii - input info

e - expression

w - weight

Method Detail

comp

public FTExpr comp(QueryContext ctx)
            throws QueryException

Description copied from class: Expr

Compiles and optimizes the expression, assigns data types and cardinalities.

Overrides:

comp in class FTExpr

Parameters:

ctx - query context

Returns:

optimized expression

Throws:

QueryException - query exception

item

public FTNode item(QueryContext ctx,
          InputInfo ii)
            throws QueryException

Description copied from class: FTExpr

This method is called by the sequential full-text evaluation.

Specified by:

item in class FTExpr

Parameters:

ctx - query context

ii - input info

Returns:

resulting item

Throws:

QueryException - query exception

iter

public FTIter iter(QueryContext ctx)

Description copied from class: FTExpr

This method is called by the index-based full-text evaluation.

Specified by:

iter in class FTExpr

Parameters:

ctx - query context

Returns:

resulting item

indexAccessible

public boolean indexAccessible(IndexContext ic)

Description copied from class: Expr

Checks if an expression can be rewritten to an index access. If this method is implemented, Expr.indexEquivalent(org.basex.query.util.IndexContext) must be implemented as well.

Overrides:

indexAccessible in class Expr

Parameters:

ic - index context

Returns:

true if an index can be used

uses

public boolean uses(Expr.Use u)

Description copied from class: Expr

Indicates if an expression uses the specified type or operation. This method is called by numerous Expr.comp(org.basex.query.QueryContext) methods to test the properties of sub-expressions. It will return true as soon as at least one test is successful.

Overrides:

uses in class FTExpr

Parameters:

u - type/operation to be found

Returns:

result of check

count

public int count(Var v)

Description copied from class: Expr

Counts how often the specified variable is used by an expression. This method is called by:

• GFLWOR.comp(org.basex.query.QueryContext) to rewrite where clauses as predicates and remove statically bound or unused clauses
• GFLWOR.compHoist(org.basex.query.QueryContext) to hoist independent variables

Overrides:

count in class FTExpr

Parameters:

v - variable to be checked

Returns:

number of occurrences

removable

public boolean removable(Var v)

Description copied from class: Expr

Checks if the specified variable is replaceable by a context item. The following tests might return false:

• Preds.removable(org.basex.query.util.Var), if one of the variables is used within a predicate.
• MixedPath.removable(org.basex.query.util.Var), if the variable occurs within the path.
• Group.removable(org.basex.query.util.Var), as the group by expression depends on variable references.

This method is called by GFLWOR.comp(org.basex.query.QueryContext) to rewrite where clauses into predicates.

Overrides:

removable in class FTExpr

Parameters:

v - variable to be replaced

Returns:

result of check

remove

public FTExpr remove(Var v)

Description copied from class: Expr

Substitutes all VarRef expressions for the given variable by a Context reference. This method is called by GFLWOR.comp(org.basex.query.QueryContext) to rewrite where clauses as predicates.

Overrides:

remove in class FTExpr

Parameters:

v - variable to be replaced

Returns:

new expression

plan

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

Description copied from class: ExprInfo

Serializes the expression tree.

Overrides:

plan in class FTExpr

Parameters:

ser - serializer

Throws:

java.io.IOException - I/O exception

toString

public java.lang.String toString()

Specified by:

toString in class ExprInfo