Package org.basex.query.expr.gflwor

Class GroupBy

java.lang.Object

org.basex.query.expr.ExprInfo

org.basex.query.expr.Expr

org.basex.query.expr.ParseExpr

org.basex.query.expr.gflwor.Clause

org.basex.query.expr.gflwor.GroupBy

public final class GroupBy
extends Clause

The GFLWOR group by expression.

Author:

BaseX Team 2005-21, BSD License, Leo Woerteler

Field Summary

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

exprType, info

Constructor Summary

Constructors

Constructor	Description
GroupBy(GroupSpec[] specs, VarRef[] pre, Var[] post, InputInfo info)	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.
void	calcSize(long[] minMax)	Calculates the minimum and maximum number of results.
void	checkUp()	Checks if the updating semantics are satisfied.
GroupBy	compile(CompileContext cc)	Compiles and optimizes the expression, assigns types and cardinalities.
GroupBy	copy(CompileContext cc, IntObjMap<Var> vm)	Copies an expression.
VarUsage	count(Var var)	Checks how often a variable or context reference is used in this expression.
boolean	equals(Object obj)	This function is e.g.
int	exprSize()	Counts the number of expressions in this expression's sub-tree.
boolean	has(Flag... flags)	Indicates if an expression has one of the specified compiler properties.
Clause	inline(InlineContext ic)	Inlines an expression into this one, replacing all variable or context references.
boolean	inlineable(InlineContext ic)	Checks if inlining is possible.
GroupBy	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.gflwor.Clause

declares, vars

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, atomItem, 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

Constructor Details

GroupBy

public GroupBy(GroupSpec[] specs,
 VarRef[] pre,
 Var[] post,
 InputInfo info)

Constructor.

Parameters:

specs - grouping specs

pre - references to pre-grouping variables

post - post-grouping variables

info - input info

Method Details

has

public 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.

Specified by:

has in class Expr

Parameters:

flags - flags to be checked

Returns:

result of check

compile

public GroupBy compile(CompileContext cc)
                throws QueryException

Description copied from class: Expr

Compiles and optimizes the expression, assigns types and cardinalities.

Specified by:

compile in class Clause

Parameters:

cc - compilation context

Returns:

optimized expression

Throws:

QueryException - query exception

optimize

public GroupBy optimize(CompileContext cc)
                 throws QueryException

Description copied from class: Expr

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

Specified by:

optimize in class Clause

Parameters:

cc - compilation context

Returns:

optimized expression

Throws:

QueryException - query exception

inlineable

public 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)

Specified by:

inlineable in class Expr

Parameters:

ic - inlining context

Returns:

result of check

count

public 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)

Specified by:

count in class Expr

Parameters:

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

Returns:

number of usages, see VarUsage

inline

public Clause 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)

Specified by:

inline in class Clause

Parameters:

ic - inlining context

Returns:

resulting expression if something has changed, null otherwise

Throws:

QueryException - query exception

copy

public GroupBy 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 Clause

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

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.

Specified by:

accept in class Expr

Parameters:

visitor - visitor

Returns:

if the walk should be continued

checkUp

public 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.

Specified by:

checkUp in class Expr

Throws:

QueryException - query exception

calcSize

public void calcSize(long[] minMax)

Description copied from class: Clause

Calculates the minimum and maximum number of results.

Overrides:

calcSize in class Clause

Parameters:

minMax - minimum and maximum number of incoming tuples

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.

Specified by:

exprSize in class Expr

Returns:

number of expressions

equals

public boolean equals(Object obj)

Description copied from class: Expr

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.

Specified by:

equals in class Expr

plan

public void plan(QueryPlan plan)

Description copied from class: ExprInfo

Creates a query plan.

Specified by:

plan in class ExprInfo

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