Package org.basex.query.expr.gflwor

Class GroupSpec

java.lang.Object

org.basex.query.expr.ExprInfo

org.basex.query.expr.Expr

org.basex.query.expr.ParseExpr

org.basex.query.expr.Single

org.basex.query.expr.gflwor.GroupSpec

public final class GroupSpec
extends Single

Grouping spec.

Author:

BaseX Team 2005-21, BSD License, Leo Woerteler

Field Summary

Fields

Modifier and Type	Field	Description
boolean	occluded	Occlusion flag, true if another grouping variable shadows this one.
final Var	var	Grouping variable.

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

expr

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

exprType, info

Constructor Summary

Constructors

Constructor	Description
GroupSpec(InputInfo info, Var var, Expr expr, Collation coll)	Constructor.

Method Summary

Modifier and Type	Method	Description
boolean	accept(ASTVisitor visitor)	Traverses this expression, notifying the visitor of declared and used variables, and checking the tree for other recursive properties.
Item	atomItem(QueryContext qc, InputInfo ii)	Evaluates the expression and returns the resulting, atomized item, or Empty.VALUE if the expression yields an empty sequence.
Expr	compile(CompileContext cc)	Compiles and optimizes the expression, assigns types and cardinalities.
Expr	copy(CompileContext cc, IntObjMap<Var> vm)	Copies an expression.
boolean	equals(Object obj)	This function is e.g.
int	exprSize()	Counts the number of expressions in this expression's sub-tree.
GroupSpec	optimize(CompileContext cc)	Optimizes an already compiled expression without recompiling its sub-expressions.
void	plan(QueryPlan plan)	Creates a query plan.
void	plan(QueryString qs)	Creates a query string.

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

checkUp, count, has, inline, inlineable

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, args, atomIter, data, data, ddo, funcType, hasFreeVars, indexAccessible, isSimple, markTailCalls, mergeEbv, simplifyFor, 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

var

public final Var var

Grouping variable.

occluded

public boolean occluded

Occlusion flag, true if another grouping variable shadows this one.

Constructor Details

GroupSpec

public GroupSpec(InputInfo info,
 Var var,
 Expr expr,
 Collation coll)

Constructor.

Parameters:

info - input info

var - grouping variable

expr - grouping expression

coll - collation (can be null)

Method Details

atomItem

public Item atomItem(QueryContext qc,
 InputInfo ii)
              throws QueryException

Description copied from class: Expr

Evaluates the expression and returns the resulting, atomized item, or Empty.VALUE if the expression yields an empty sequence.

Overrides:

atomItem in class Expr

Parameters:

qc - query context

ii - input info (only required by Seq instances, which have no input info)

Returns:

item or Empty.VALUE

Throws:

QueryException - query exception

copy

public Expr copy(CompileContext cc,
 IntObjMap<Var> vm)

Description copied from class: Expr

Copies an expression. Used for inlining functions, or for copying static queries. It is utilized by VarRef.inline(org.basex.query.InlineContext), FuncItem.inline(org.basex.query.expr.Expr[], org.basex.query.CompileContext), Closure.inline(org.basex.query.InlineContext) and StaticFunc.inline(org.basex.query.expr.Expr[], org.basex.query.CompileContext).

Specified by:

copy in class Expr

Parameters:

cc - compilation context

vm - mapping from old variable IDs to new variable copies. Required by Closure.copy(org.basex.query.CompileContext, org.basex.util.hash.IntObjMap<org.basex.query.var.Var>) and VarRef.copy(org.basex.query.CompileContext, org.basex.util.hash.IntObjMap<org.basex.query.var.Var>)

Returns:

copied expression

compile

public Expr compile(CompileContext cc)
             throws QueryException

Description copied from class: Expr

Compiles and optimizes the expression, assigns types and cardinalities.

Overrides:

compile in class Single

Parameters:

cc - compilation context

Returns:

optimized expression

Throws:

QueryException - query exception

optimize

public GroupSpec optimize(CompileContext cc)
                   throws QueryException

Description copied from class: Expr

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

Overrides:

optimize in class Single

Parameters:

cc - compilation context

Returns:

optimized expression

Throws:

QueryException - query exception

accept

public 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 Single

Parameters:

visitor - visitor

Returns:

if the walk should be continued

exprSize

public 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 Single

Returns:

number of expressions

equals

public boolean equals(Object obj)

Description copied from class: Single

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 Single

plan

public void plan(QueryPlan plan)

Description copied from class: ExprInfo

Creates a query plan.

Overrides:

plan in class Single

Parameters:

plan - expression plan

plan

public void plan(QueryString qs)

Description copied from class: ExprInfo

Creates a query string.

Specified by:

plan in class ExprInfo

Parameters:

qs - query string builder