org.basex.query.ft

Class FTExpr

java.lang.Object

org.basex.data.ExprInfo

org.basex.query.expr.Expr

org.basex.query.expr.ParseExpr

org.basex.query.ft.FTExpr

Direct Known Subclasses:

FTAnd, FTExtensionSelection, FTFilter, FTMildNot, FTNot, FTOptions, FTOr, FTWeight, FTWords

public abstract class FTExpr
extends ParseExpr

This class defines is an abstract class for full-text expressions.

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

Modifier and Type	Field and Description
FTExpr[]	expr Expression list.

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

input, size, type

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.
FTExpr	indexEquivalent(IndexContext ic) Returns an equivalent expression which accesses an index structure.
abstract FTNode	item(QueryContext ctx, InputInfo ii) This method is called by the sequential full-text evaluation.
abstract 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.
boolean	uses(Expr.Use u) Indicates if an expression uses the specified type or operation.

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, indexAccessible, isEmpty, isFunction, isItem, isVacuous, isValue, iterable, markTailCalls, sameAs

Methods inherited from class org.basex.data.ExprInfo

description, info, toString

Methods inherited from class java.lang.Object

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

Field Detail

expr

public final FTExpr[] expr

Expression list.

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.

Specified by:

comp in class Expr

Parameters:

ctx - query context

Returns:

optimized expression

Throws:

QueryException - query exception

item

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

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

Overrides:

item in class ParseExpr

Parameters:

ctx - query context

ii - input info

Returns:

resulting item

Throws:

QueryException - query exception

iter

public abstract FTIter iter(QueryContext ctx)
                     throws QueryException

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

Overrides:

iter in class ParseExpr

Parameters:

ctx - query context

Returns:

resulting item

Throws:

QueryException - query exception

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.

Specified by:

uses in class Expr

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

Specified by:

count in class Expr

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.

Specified by:

removable in class Expr

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.

Specified by:

remove in class Expr

Parameters:

v - variable to be replaced

Returns:

new expression

indexEquivalent

public FTExpr indexEquivalent(IndexContext ic)
                       throws QueryException

Description copied from class: Expr

Returns an equivalent expression which accesses an index structure. Will be called if Expr.indexAccessible(org.basex.query.util.IndexContext) is returns true for an expression.

Overrides:

indexEquivalent in class Expr

Parameters:

ic - index context

Returns:

equivalent index-expression

Throws:

QueryException - query exception

plan

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

Description copied from class: ExprInfo

Serializes the expression tree.

Specified by:

plan in class ExprInfo

Parameters:

ser - serializer

Throws:

java.io.IOException - I/O exception