Package org.basex.query.expr

Class Filter

java.lang.Object

org.basex.query.expr.ExprInfo

org.basex.query.expr.Expr

org.basex.query.expr.ParseExpr

org.basex.query.expr.Arr

org.basex.query.expr.Preds

org.basex.query.expr.Filter

Direct Known Subclasses:

CachedFilter, IterFilter

public abstract class Filter
extends Preds

Abstract filter expression.

Author:

BaseX Team 2005-21, BSD License, Christian Gruen

Field Summary

Fields

Modifier and Type	Field	Description
Expr	root	Expression.

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

exprs

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

exprType, info

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	Filter(InputInfo info, Expr root, Expr... exprs)	Constructor.

Method Summary

Modifier and Type	Method	Description
final boolean	accept(ASTVisitor visitor)	Traverses this expression, notifying the visitor of declared and used variables, and checking the tree for other recursive properties.
final Expr	addPredicate(CompileContext cc, Expr pred)	Adds a predicate and returns the optimized expression.
final void	checkUp()	Checks if the updating semantics are satisfied.
final Expr	compile(CompileContext cc)	Compiles and optimizes the expression, assigns types and cardinalities.
final VarUsage	count(Var var)	Checks how often a variable or context reference is used in this expression.
final Data	data()	Returns the data reference bound to this expression.
boolean	ddo()	Indicates if this expression returns nodes in document order without duplicates.
final boolean	equals(Object obj)	This function is e.g.
final int	exprSize()	Counts the number of expressions in this expression's sub-tree.
static Expr	get(CompileContext cc, InputInfo ii, Expr root, Expr... preds)	Creates a new, optimized filter expression, or the root expression if no predicates exist.
final boolean	has(Flag... flags)	Indicates if an expression has one of the specified compiler properties.
final Expr	inline(InlineContext ic)	Inlines an expression into this one, replacing all variable or context references.
final boolean	inlineable(InlineContext ic)	Checks if inlining is possible.
final Expr	optimize(CompileContext cc)	Optimizes an already compiled expression without recompiling its sub-expressions.
final void	plan(QueryPlan plan)	Creates a query plan.
final void	plan(QueryString qs)	Creates a query string.
final Expr	simplifyCount(CompileContext cc)	Rewrites a filter expression for count operations.
final Expr	simplifyFor(CompileContext.Simplify mode, CompileContext cc)	This function is called at compile time for expressions whose operands might be simplified.
protected final void	type(Expr expr)	Assigns the expression type.

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

flattenEbv, match, mayBePositional, numeric, simplify

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

allAreValues, args, copyAll, flatten, inline, mayBePositional, simplifyAll

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

adoptType, atomValue, checkAllUp, checkNoEmpty, checkNoEmpty, checkNoneUp, checkNoUp, checkType, checkType, checkUp, copyType, ctxValue, ebv, item, iter, refineType, seqType, size, test, toArray, toArray, toAtomItem, toB64, toB64, toBin, toBin, toBoolean, toBoolean, toBytes, toBytes, toDouble, toDouble, toElem, toFloat, toFunc, toItem, toItem, toLong, toLong, toMap, toMap, toNode, toNode, toNodeOrNull, toNumber, toNumberOrNull, toQNm, toQNm, toToken, toToken, toTokenOrNull, toZeroToken, value

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

arg, atomItem, atomIter, copy, data, funcType, hasFreeVars, indexAccessible, isSimple, markTailCalls, mergeEbv, typeCheck, uses, vacuous, visitAll

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

description, toErrorString, toString

Methods inherited from class java.lang.Object

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

Field Details

root

public Expr root

Expression.

Constructor Details

Filter

protected Filter(InputInfo info,
 Expr root,
 Expr... exprs)

Constructor.

Parameters:

info - input info

root - root expression

exprs - predicate expressions

Method Details

get

public static Expr get(CompileContext cc,
 InputInfo ii,
 Expr root,
 Expr... preds)
                throws QueryException

Creates a new, optimized filter expression, or the root expression if no predicates exist.

Parameters:

cc - compilation context

ii - input info

root - root expression

preds - predicate expressions

Returns:

filter root, path or filter expression

Throws:

QueryException - query exception

checkUp

public final void checkUp()
                   throws QueryException

Description copied from class: Expr

Checks if the updating semantics are satisfied. This function is only called if any updating expression was found in the query.

Overrides:

checkUp in class Arr

Throws:

QueryException - query exception

compile

public final Expr compile(CompileContext cc)
                   throws QueryException

Description copied from class: Expr

Compiles and optimizes the expression, assigns types and cardinalities.

Overrides:

compile in class Preds

Parameters:

cc - compilation context

Returns:

optimized expression

Throws:

QueryException - query exception

optimize

public final Expr optimize(CompileContext cc)
                    throws QueryException

Description copied from class: Expr

Optimizes an already compiled expression without recompiling its sub-expressions.

Overrides:

optimize in class Expr

Parameters:

cc - compilation context

Returns:

optimized expression

Throws:

QueryException - query exception

type

protected final void type(Expr expr)

Description copied from class: Preds

Assigns the expression type.

Specified by:

type in class Preds

Parameters:

expr - root expression

addPredicate

public final Expr addPredicate(CompileContext cc,
 Expr pred)
                        throws QueryException

Adds a predicate and returns the optimized expression. This function is e.g. called by ForLet.addPredicate(org.basex.query.CompileContext, org.basex.query.expr.Expr).

Parameters:

cc - compilation context

pred - predicate to be added

Returns:

new filter

Throws:

QueryException - query exception

simplifyCount

public final Expr simplifyCount(CompileContext cc)
                         throws QueryException

Rewrites a filter expression for count operations.

Parameters:

cc - compilation context

Returns:

optimized or original expression.

Throws:

QueryException - query exception

simplifyFor

public final Expr simplifyFor(CompileContext.Simplify mode,
 CompileContext cc)
                       throws QueryException

Description copied from class: Expr

This function is called at compile time for expressions whose operands might be simplified.

Overrides:

simplifyFor in class Expr

Parameters:

mode - mode of simplification

cc - compilation context

Returns:

simplified or original expression

Throws:

QueryException - query exception

See Also:

• CompileContext.Simplify

has

public final boolean has(Flag... flags)

Description copied from class: Expr

Indicates if an expression has one of the specified compiler properties. This method must only be called at compile time. It is invoked to test properties of sub-expressions. It returns true if at least flag matches an expression.

Overrides:

has in class Arr

Parameters:

flags - flags to be checked

Returns:

result of check

inlineable

public final boolean inlineable(InlineContext ic)

Description copied from class: Expr

Checks if inlining is possible. This function is called by InlineContext.inlineable(org.basex.query.expr.Expr...) and: CNode.inlineable(org.basex.query.InlineContext) returns false if the new expression construct new nodes. The following tests might reject inlining if the expression is a context reference:

• Preds.inlineable(org.basex.query.InlineContext)
• Path.inlineable(org.basex.query.InlineContext)
• SimpleMap.inlineable(org.basex.query.InlineContext)
• StaticJavaCall.inlineable(org.basex.query.InlineContext)
• TransformWith.inlineable(org.basex.query.InlineContext)

Overrides:

inlineable in class Preds

Parameters:

ic - inlining context

Returns:

result of check

count

public final VarUsage count(Var var)

Description copied from class: Expr

Checks how often a variable or context reference is used in this expression. This function is called by:

• Closure.optimize(org.basex.query.CompileContext)
• GFLWOR.inlineForLet(org.basex.query.CompileContext)
• GFLWOR.optimizePos(org.basex.query.CompileContext)
• GFLWOR.simplify(org.basex.query.CompileContext)
• GFLWOR.unusedVars(org.basex.query.CompileContext)
• SimpleMap.optimize(org.basex.query.CompileContext)
• TypeswitchGroup.optimize(org.basex.query.CompileContext)

Overrides:

count in class Arr

Parameters:

var - variable (Var reference) or context (null) to inline

Returns:

number of usages, see VarUsage

inline

public final Expr inline(InlineContext ic)
                  throws QueryException

Description copied from class: Expr

Inlines an expression into this one, replacing all variable or context references. This function is called by InlineContext.inline(Expr) (see invocations of this functions for further inlinings). The variable reference is replaced in:

• OrderBy.inline(org.basex.query.InlineContext)
• VarRef.inline(org.basex.query.InlineContext)

The context is replaced in:

• ContextFn.inline(org.basex.query.InlineContext)
• ContextValue.inline(org.basex.query.InlineContext)
• Arr.inline(org.basex.query.InlineContext)

Overrides:

inline in class Arr

Parameters:

ic - inlining context

Returns:

resulting expression if something has changed, null otherwise

Throws:

QueryException - query exception

data

public final 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)

accept

public final boolean accept(ASTVisitor visitor)

Description copied from class: Expr

Traverses this expression, notifying the visitor of declared and used variables, and checking the tree for other recursive properties.

Overrides:

accept in class Arr

Parameters:

visitor - visitor

Returns:

if the walk should be continued

ddo

public boolean ddo()

Description copied from class: Expr

Indicates if this expression returns nodes in document order without duplicates.

Overrides:

ddo in class Expr

Returns:

result of check

exprSize

public final int exprSize()

Description copied from class: Expr

Counts the number of expressions in this expression's sub-tree. This method is e.g. called by StaticFunc.inline(org.basex.query.expr.Expr[], org.basex.query.CompileContext) to check if an expression is small enough to be inlined.

Overrides:

exprSize in class Arr

Returns:

number of expressions

equals

public final boolean equals(Object obj)

Description copied from class: Arr

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) or Pos.get(Expr, CmpV.OpV, InputInfo, CompileContext), in order to compare the start and end value.
• PathCache, in order to find identical root values at runtime.

Must be overwritten by implementing class.

Overrides:

equals in class Arr

plan

public final void plan(QueryPlan plan)

Description copied from class: ExprInfo

Creates a query plan.

Overrides:

plan in class Arr

Parameters:

plan - expression plan

plan

public final void plan(QueryString qs)

Description copied from class: ExprInfo

Creates a query string.

Overrides:

plan in class Preds

Parameters:

qs - query string builder