ForExpression Class Reference

Represents an XQuery for-loop. More...

#include <forexpression.h>

Inheritance diagram for ForExpression:

Collaboration diagram for ForExpression:

List of all members.

Public Member Functions

ForExpression (VarExpression *_var, VarExpression *_varexp, Expression *_exp)

Constructor.

ForExpression (VarExpression *_var, VarStepExpression *_varstep, Expression *_exp)

Constructor.

virtual ~ForExpression ()

virtual void scopeCheck (vector< unsigned > &def_vars, vector< unsigned > &introduced_vars, vector< unsigned > &violating_vars)

virtual void replaceVarId (unsigned old_id, unsigned new_id)

virtual void mergeSequences ()

virtual void extractFSAMap (FSAMap *fsamap, unsigned parent_var)

virtual void extractParVarMap (ParVarMap *parvarmap)

virtual void extractDependencies (vector< DependencySet * > *depset)

virtual Expression * placeSignOffs (vector< SignOffExpression * > &signoffs)

virtual void rewriteWhereExps ()

virtual void rewriteEmptyFuncts ()

virtual void rewriteVarstepCondExps ()

virtual void rewriteAggregateFuncts ()

virtual void rewriteVarsteps ()

virtual void print (OutputStream &dos) const

virtual void init (BufferNode *root)

virtual void eval (OutputStream &eos, Environment *env, unsigned modus)

virtual void evalSignOffForBinding (OutputStream &eos, Environment *env, BufferNode *cur)

Executes all signOff statements in a for-loop.

virtual bool containsDirectOutput ()

Private Attributes

VarExpression * var

The entered VarExpression.

VarExpression * varexp

The entered VarExpression.

VarStepExpression * varstep

The entered VarStepExpression.

Expression * exp

The entered Expression.

BufferIterator * bit

The initialized BufferIterator for the entered VarExpression or VarStepExpression.

Detailed Description

Represents an XQuery for-loop.

Represents an XQuery for-loop, which takes a VarExpression, a VarExpression or a VarStepExpression and a Expression, e.g. for $x in /bib//book return $x/title or for $y in $x return $y//book, as arguments and introduces a new variable or returns the next new variable binding of the entered VarExpression or VarStepExpression respectively.

Author:: Michael Schmidt
Gunnar Jehl

Version:: 2.1

License:: Software License Agreement (BSD License)

Definition at line 54 of file forexpression.h.

Constructor & Destructor Documentation

ForExpression::ForExpression	(	VarExpression *	_var,
		VarExpression *	_varexp,
		Expression *	_exp
	)

Constructor.

Constructor - creating object for two VarExpression and a Expression.

Parameters:

`[in]`	_var	Pointer to a VarExpression object.
`[in]`	_varexp	Pointer to a VarExpression object.
`[in]`	_exp	Pointer to a Expression object.

Definition at line 37 of file forexpression.cpp.

Referenced by rewriteVarsteps().

ForExpression::ForExpression	(	VarExpression *	_var,
		VarStepExpression *	_varstep,
		Expression *	_exp
	)

Constructor.

Constructor - creating object for a VarExpression, a VarStepExpression an a Expression.

Parameters:

`[in]`	_var	Pointer to a VarExpression object.
`[in]`	_varstep	Pointer to a VarStepExpression object.
`[in]`	_exp	Pointer to a Expression object.

Definition at line 42 of file forexpression.cpp.

ForExpression::~ForExpression ( ) [virtual]

Destructor.

Definition at line 47 of file forexpression.cpp.

References bit, exp, var, varexp, and varstep.

Member Function Documentation

bool ForExpression::containsDirectOutput ( ) [virtual]

Returns if the corresponding expression produces direct output.

Returns if the corresponding expression produces direct output. Direct output is meant that this subexpression produces output such as node constructs or strings.

Return values:

bool true if the corresponding expression produces direct output, false otherwise.

Reimplemented from Expression.

Definition at line 292 of file forexpression.cpp.

References Expression::containsDirectOutput(), exp, and Expression::getType().

Referenced by extractParVarMap().

void ForExpression::eval	(	OutputStream &	eos,
		Environment *	env,
		unsigned	modus
	)			`[virtual]`

Evaluates the expression in the given environment.

Evaluates the expression in the given environment. The evaluation takes place in the environment that is passed to this method. In addition, the parameter modus is one of the following: EVAL_QUERY, EVAL_QUERY_SILENT or EVAL_SIGNOFF (see also the corresponding defines for more information). This method implements the XQuery semantics for the standard expression types, but also the GCX specific extensions like signOff-statements.

Parameters:

`[in]`	eos	Pointer to a OutputStream object.
`[in]`	env	Pointer to an Environment object.
`[in]`	modus	The query evaluation mode.

Exceptions:

RuntimeException

If illegal evaluation mode.

Reimplemented from Expression.

Definition at line 228 of file forexpression.cpp.

References bit, BufferIterator::clear(), Environment::clone(), Expression::eval(), EVAL_QUERY, EVAL_SIGNOFF, exp, VarExpression::getId(), BufferIterator::getNext(), Environment::getNodeBinding(), BufferIterator::init(), Environment::insertNodeBinding(), LOCK_CONTEXT_ALWAYS_CLEAR, READ_UP_TO_CLOSE_NONE, var, varexp, and varstep.

Referenced by AggregateFunctVarSampExpression::eval(), AggregateFunctVarPopExpression::eval(), AggregateFunctSumExpression::eval(), AggregateFunctStdDevSampExpression::eval(), AggregateFunctStdDevPopExpression::eval(), AggregateFunctMinExpression::eval(), AggregateFunctMedianExpression::eval(), AggregateFunctMaxExpression::eval(), AggregateFunctCountExpression::eval(), and AggregateFunctAvgExpression::eval().

void ForExpression::evalSignOffForBinding	(	OutputStream &	eos,
		Environment *	env,
		BufferNode *	cur
	)			`[virtual]`

Executes all signOff statements in a for-loop.

Executes all signOff statements in a for-loop by binding the for-loop iteration variable to a BufferNode (creating a new Environment) and executing all SignOffExpression in this Environment.

Parameters:

`[in]`	eos	Pointer to a OutputStream object.
`[in]`	env	Pointer to a Environment object.
`[in]`	cur	Pointer to a BufferNode object.

Return values:

void

Definition at line 282 of file forexpression.cpp.

References Environment::clone(), Expression::eval(), EVAL_SIGNOFF, exp, VarExpression::getId(), Environment::insertNodeBinding(), and var.

void ForExpression::extractDependencies ( vector< DependencySet * > * depset ) [virtual]

Extracts the needed dependencies of a query.

Extracts the needed dependencies of a query, which are needed for constructing the ProjectionTree.

Parameters:

[in,out] depset Pointer to a vector containing Pointer to DependencySet objects.

Return values:

void

Reimplemented from Expression.

Definition at line 146 of file forexpression.cpp.

References exp, and Expression::extractDependencies().

Referenced by AggregateFunctExpression::extractDependencies().

void ForExpression::extractFSAMap	(	FSAMap *	fsamap,
		unsigned	parent_var
	)			`[virtual]`

Extracts the needed first straight ancestor (FSA) variables map.

Extracts the needed first straight ancestor (FSA) variables map, which is needed for correct insertion of SignOffExpression.

Parameters:

`[in,out]`	fsamap	Pointer to a FSAMap object.
`[in]`	parent_var	Parent variable.

Return values:

void

Reimplemented from Expression.

Definition at line 117 of file forexpression.cpp.

References exp, Expression::extractFSAMap(), FSAMap::getFSA(), VarExpression::getId(), FSAMap::insertFSA(), var, varexp, and varstep.

Referenced by AggregateFunctExpression::extractFSAMap().

void ForExpression::extractParVarMap ( ParVarMap * parvarmap ) [virtual]

Extracts the needed parent variable (ParVar) map.

Extracts the needed parent variable (ParVar) map, which is needed for constructing the VariableTree.

Parameters:

[in,out] parvarmap Pointer to a ParVarMap object.

Return values:

void

Reimplemented from Expression.

Definition at line 134 of file forexpression.cpp.

References containsDirectOutput(), exp, Expression::extractParVarMap(), VarExpression::getId(), VarStepExpression::getPath(), ParVarMap::insertParVar(), var, varexp, and varstep.

Referenced by AggregateFunctExpression::extractParVarMap().

void ForExpression::init ( BufferNode * root ) [virtual]

Initializes the query for evaluation.

Initializes the query for evaluation. Up to now only all required BufferIterator objects are created to speed up query evaluation.

Parameters:

[in] root Pointer to a BufferNode object.

Return values:

void

Reimplemented from Expression.

Definition at line 218 of file forexpression.cpp.

References bit, exp, Expression::init(), varexp, and varstep.

Referenced by AggregateFunctExpression::init().

void ForExpression::mergeSequences ( ) [virtual]

Merges belonging together XQuery sequences into a single sequence.

Merges belonging together XQuery sequences into a single sequence, which is done because of better/nicer output look.

Return values:

void

Reimplemented from Expression.

Definition at line 113 of file forexpression.cpp.

References exp, and Expression::mergeSequences().

Expression * ForExpression::placeSignOffs ( vector< SignOffExpression * > & signoffs ) [virtual]

Places all signOff-statements in the corresponding query.

Places all signOff-statements in the corresponding query, which are needed for active garbage collection by removing Role from the BufferNode.

Parameters:

[in] signoffs Pointer to a vector containing Pointer to SignOffExpression objects.

Return values:

Expression*

Pointer to a Expression object (following expression in the corresponding query).

Reimplemented from Expression.

Definition at line 150 of file forexpression.cpp.

References exp, VarExpression::getId(), Expression::placeSignOffs(), and var.

Referenced by AggregateFunctExpression::placeSignOffs().

void ForExpression::print ( OutputStream & dos ) const [virtual]

Prints the expression.

Parameters:

[in] dos Pointer to a OutputStream object.

Return values:

void

Implements Expression.

Definition at line 195 of file forexpression.cpp.

References decrementIndents(), exp, Expression::getType(), incrementIndents(), NEWLINE, varexp, and writeIndents().

void ForExpression::replaceVarId	(	unsigned	old_id,
		unsigned	new_id
	)			`[virtual]`

Replaces all matching variable IDs by a new one.

Replaces all matching variable IDs by a new one, which is needed in case of calling method rewriteVarsteps().

Parameters:

`[in]`	old_id	Old variable ID.
`[in]`	new_id	New variable ID, which should be introduced instead.

Return values:

void

Reimplemented from Expression.

Definition at line 98 of file forexpression.cpp.

References exp, VarExpression::getId(), VarName::getInstance(), Expression::replaceVarId(), VarExpression::replaceVarId(), TAGID_ROOT, var, varexp, and varstep.

void ForExpression::rewriteAggregateFuncts ( ) [virtual]

Rewrites all arguments of all aggregate functions into an equivalent for-clause (with return-clause).

Return values:

void

Reimplemented from Expression.

Definition at line 176 of file forexpression.cpp.

References exp, and Expression::rewriteAggregateFuncts().

void ForExpression::rewriteEmptyFuncts ( ) [virtual]

Rewrites all fn:empty XQuery functions into equivalent fn:not(fn:exists) XQuery functions.

Return values:

void

Reimplemented from Expression.

Definition at line 168 of file forexpression.cpp.

References exp, and Expression::rewriteEmptyFuncts().

void ForExpression::rewriteVarstepCondExps ( ) [virtual]

Rewrites all if($x) if-conditions into equivalent if(fn:not(fn:empty($x))) XQuery expressions.

Return values:

void

Reimplemented from Expression.

Definition at line 172 of file forexpression.cpp.

References exp, and Expression::rewriteVarstepCondExps().

void ForExpression::rewriteVarsteps ( ) [virtual]

Rewrites all varstep expressions, which produces output into an equivalent for-clause (with return-clause).

Rewrites all varstep expressions, which produces output into an equivalent for-clause (with return-clause). This method belongs to the 'earlier execution of signoff-statements' optimization.

Return values:

void

Reimplemented from Expression.

Definition at line 180 of file forexpression.cpp.

References VarExpression::clone(), exp, ForExpression(), VarName::getInstance(), Expression::getType(), and Expression::rewriteVarsteps().

void ForExpression::rewriteWhereExps ( ) [virtual]

Rewrites all where-clauses in the query into equivalent if-expressions.

Rewrites all where-clauses in the query into equivalent if-expressions, i.e. rewrites all WhereExpression into equivalent IfExpression.

Return values:

void

Reimplemented from Expression.

Definition at line 164 of file forexpression.cpp.

References exp, and Expression::rewriteWhereExps().

void ForExpression::scopeCheck	(	vector< unsigned > &	def_vars,
		vector< unsigned > &	introduced_vars,
		vector< unsigned > &	violating_vars
	)			`[virtual]`

Returns if all used variables were previously (through a for-clause) defined or if a variable leaves their defined scope.

Parameters:

`[in]`	def_vars	Vector containing all previously defined variables.
`[in]`	introduced_vars	Vector containing all up to this expression defined variables.
`[in]`	violating_vars	Vector containing all variables which violates the scope condition.

Return values:

void

Reimplemented from Expression.

Definition at line 55 of file forexpression.cpp.

References exp, VarExpression::getId(), VarName::getInstance(), VarName::getVarname(), VarName::insertVarname(), Expression::replaceVarId(), Expression::scopeCheck(), VarExpression::scopeCheck(), VarExpression::setId(), TAGID_ROOT, var, varexp, and varstep.

Member Data Documentation

BufferIterator * ForExpression::bit [private]

The initialized BufferIterator for the entered VarExpression or VarStepExpression.

The initialized BufferIterator for the entered VarExpression or VarStepExpression after calling method init(). This member variable is NULL on creation of object but should not be NULL anymore after method init() has been executed.

Definition at line 211 of file forexpression.h.

Referenced by eval(), init(), and ~ForExpression().

Expression * ForExpression::exp [private]

The entered Expression.

The entered Expression, which is the third argument of the constructor and defines the return-clause of a for-loop.

Definition at line 203 of file forexpression.h.

Referenced by containsDirectOutput(), eval(), evalSignOffForBinding(), extractDependencies(), extractFSAMap(), extractParVarMap(), init(), mergeSequences(), placeSignOffs(), print(), replaceVarId(), rewriteAggregateFuncts(), rewriteEmptyFuncts(), rewriteVarstepCondExps(), rewriteVarsteps(), rewriteWhereExps(), scopeCheck(), and ~ForExpression().

VarExpression * ForExpression::var [private]

The entered VarExpression.

The entered VarExpression, which is the first argument of the constructor and defines a new introduced variable of a for-loop.

Definition at line 180 of file forexpression.h.

Referenced by eval(), evalSignOffForBinding(), extractFSAMap(), extractParVarMap(), placeSignOffs(), replaceVarId(), scopeCheck(), and ~ForExpression().

VarExpression * ForExpression::varexp [private]

The entered VarExpression.

The entered VarExpression, which is the second argument of the constructor and defines the iteration base, i.e. the sequence of nodes for iteration, of a for-loop. This member variable is NULL if the constructor was called with a VarStepExpression.

Definition at line 188 of file forexpression.h.

Referenced by eval(), extractFSAMap(), extractParVarMap(), init(), print(), replaceVarId(), scopeCheck(), and ~ForExpression().

VarStepExpression * ForExpression::varstep [private]

The entered VarStepExpression.

The entered VarStepExpression, which is the second argument of the constructor and defines the iteration base, i.e. the sequence of nodes for iteration, of a for-loop. This member variable is NULL if the constructor was called with a VarExpression.

Definition at line 196 of file forexpression.h.

Referenced by eval(), extractFSAMap(), extractParVarMap(), init(), replaceVarId(), scopeCheck(), and ~ForExpression().


Public Member Functions
	ForExpression (VarExpression _var, VarExpression _varexp, Expression *_exp)
	Constructor.
	ForExpression (VarExpression _var, VarStepExpression _varstep, Expression *_exp)
	Constructor.
virtual	~ForExpression ()
virtual void	scopeCheck (vector< unsigned > &def_vars, vector< unsigned > &introduced_vars, vector< unsigned > &violating_vars)
virtual void	replaceVarId (unsigned old_id, unsigned new_id)
virtual void	mergeSequences ()
virtual void	extractFSAMap (FSAMap *fsamap, unsigned parent_var)
virtual void	extractParVarMap (ParVarMap *parvarmap)
virtual void	extractDependencies (vector< DependencySet * > *depset)
virtual Expression *	placeSignOffs (vector< SignOffExpression * > &signoffs)
virtual void	rewriteWhereExps ()
virtual void	rewriteEmptyFuncts ()
virtual void	rewriteVarstepCondExps ()
virtual void	rewriteAggregateFuncts ()
virtual void	rewriteVarsteps ()
virtual void	print (OutputStream &dos) const
virtual void	init (BufferNode *root)
virtual void	eval (OutputStream &eos, Environment *env, unsigned modus)
virtual void	evalSignOffForBinding (OutputStream &eos, Environment env, BufferNode cur)
	Executes all signOff statements in a for-loop.
virtual bool	containsDirectOutput ()
Private Attributes
VarExpression *	var
	The entered VarExpression.
VarExpression *	varexp
	The entered VarExpression.
VarStepExpression *	varstep
	The entered VarStepExpression.
Expression *	exp
	The entered Expression.
BufferIterator *	bit
	The initialized BufferIterator for the entered VarExpression or VarStepExpression.