Provides access to fast ( O(log n) ) bi-directional lookups on a specified relation. More...

#include <RelationIndex.h>

Collaboration diagram for RelationIndex< FROM, TO >:

Public Types
typedef RelationIndexContainer< FROM, TO >::Element	Element
	Struct representing a single element in the index.

typedef RelationIndexContainer< FROM, TO >::ElementIndex	ElementIndex
	Class representing a the index on the relation.

typedef ElementIndex::template nth_index< 0 >::type	index_from
	Typedef for easy access to the from side of the index.

typedef ElementIndex::template nth_index< 1 >::type	index_to
	Typedef for easy access to the to side of the index.

typedef index_from::const_iterator	iterator_from
	Element iterator of the from side index. More...

typedef index_to::const_iterator	iterator_to
	Element iterator of the to side index.

typedef boost::iterator_range< iterator_from >	range_from
	Iterator range [first,second) of the from side.

typedef boost::iterator_range< iterator_to >	range_to
	Iterator range [first,second) of the to side.

Public Member Functions
	RelationIndex (const std::string &name=(DataStore::defaultRelationName< FROM, TO >()), DataStore::EDurability durability=DataStore::c_Event)
	Constructor. More...

	RelationIndex (const StoreArray< FROM > &from, const StoreArray< TO > &to, const std::string &name="", DataStore::EDurability durability=DataStore::c_Event)
	Constructor with checks. More...

	operator bool () const
	check if index is based on valid relation.

range_from	getElementsFrom (const FROM *from) const
	Return a range of all elements pointing from the given object. More...

range_from	getElementsFrom (const FROM &from) const
	Return a range of all elements pointing from the given object. More...

range_to	getElementsTo (const TO *to) const
	Return a range of all elements pointing to the given object. More...

range_to	getElementsTo (const TO &to) const
	Return a range of all elements pointing to the given object. More...

const Element *	getFirstElementFrom (const FROM &from) const
	Return a pointer to the first relation Element of the given object. More...

const Element *	getFirstElementFrom (const FROM *from) const
	Return a pointer to the first relation Element of the given object. More...

const Element *	getFirstElementTo (const TO &to) const
	Return a pointer to the first relation Element of the given object. More...

const Element *	getFirstElementTo (const TO *to) const
	Return a pointer to the first relation Element of the given object. More...

AccessorParams	getAccessorParams () const
	Get the AccessorParams of the underlying relation.

const AccessorParams &	getFromAccessorParams () const
	Get the AccessorParams of the StoreArray the relation points from.

const AccessorParams &	getToAccessorParams () const
	Get the AccessorParams of the StoreArray the relation points to.

size_t	size () const
	Get the size of the index.

Protected Attributes
const std::shared_ptr< RelationIndexContainer< FROM, TO > >	m_index
	Reference to the IndexContainer.

const index_from &	m_from
	Reference to the from index.

const index_to &	m_to
	Reference to the to index.

Detailed Description

template<class FROM, class TO>
class Belle2::RelationIndex< FROM, TO >

Provides access to fast ( O(log n) ) bi-directional lookups on a specified relation.

Note: This class is used internally by RelationsObject/RelationsInterface. In most cases, you should avoid using RelationIndex directly and use these more friendly interfaces.

Relations connect objects stored in two StoreArrays with each other, with the possibility of n:n connections and individual weights.

This class provides bidirectional access to a given relation to ease use of Relations for the normal user. There is no support for changing or adding Elements of the relation, this should be done directly using RelationArray.

Finding related objects

Given an object of type FROM or TO, RelationIndex can easily find objects on the other side connected to it. If there can be at most one relation from/to the given objects, this is especially simple:

RelationIndex<MCParticle, CDCSimHit> mcparticlesToCdcsimhits;
if(!mcparticlesToCdcsimhits)
  B2FATAL("No MCParticle -> CDCSimHit relation found!");
 
typedef RelationIndex<MCParticle, CDCSimHit>::Element relElement_t;
for(int iCDC = 0; iCDC < cdcsimhits.getEntries(); iCDC++) {
  const CDCSimHit* hit = cdcsimhits[iCDC];
 
  //assuming 'hit' was only created by a single particle
  const relElement_t* rel = mcparticlesToCdcsimhits.getFirstElementTo(hit);
  if(!rel) {
    B2WARNING("no MCParticle found for CDCSimHit " << iCDC);
    continue;
  }
  B2INFO("this CDCHit came from a particle with PDG code " << rel->from->getPDG());
}

If more than one associated object exists, one can loop over them using range-based for. For example, when one instead wants to find the CDCSimHits belonging to a particle, one can use:

const MCParticle* particle = ...;
for(const relElement_t & rel: mcparticlesToCdcsimhits.getElementsFrom(particle)) {
  const CDCSimHit* hit = rel.to;
  //...
}

The documentation of the relation element type used by getFirstElementTo()/ getFirstElementFrom() or during the for loop can be found in RelationIndexContainer<FROM, TO>::Element.

See also: See RelationArray for examples on how to create new relations between objects.

Definition at line 76 of file RelationIndex.h.

Member Typedef Documentation

◆ iterator_from

typedef index_from::const_iterator iterator_from

Element iterator of the from side index.

Note: Both iterator_from and iterator_to point to objects of type Element, but reflect the structure of the underlying index.

Definition at line 95 of file RelationIndex.h.

Constructor & Destructor Documentation

◆ RelationIndex() [1/2]

RelationIndex	(	const std::string &	name = `(DataStore::defaultRelationName<FROM, TO>())`,
		DataStore::EDurability	durability = `DataStore::c_Event`
	)

inlineexplicit

Constructor.

Parameters

name	Name of the relation. Empty string will be replaced with the default relation name for the given types
durability	Durabiliy of the relation

Definition at line 113 of file RelationIndex.h.

                                                                               :
       m_index(RelationIndexManager::Instance().get<FROM, TO>(RelationArray(name, durability))),
       m_from(m_index->index().template get<0>()),
       m_to(m_index->index().template get<1>()) {}

◆ RelationIndex() [2/2]

RelationIndex	(	const StoreArray< FROM > &	from,
		const StoreArray< TO > &	to,
		const std::string &	name = `""`,
		DataStore::EDurability	durability = `DataStore::c_Event`
	)

inline

Constructor with checks.

This constructor takes the StoreArrays as arguments to perform additional sanity checks if the relation is correct.

Parameters

from	StoreArray the relation is supposed to point from
to	StoreArray the relation is supposed to point to
name	Name of the relation. Empty string will be replaced with the default relation name for the given types
durability	Durabiliy of the relation

Definition at line 131 of file RelationIndex.h.

Member Function Documentation

◆ getElementsFrom() [1/2]

range_from getElementsFrom ( const FROM & from ) const

inline

Return a range of all elements pointing from the given object.

Can be used with range-based for, see RelationIndex class documentation for an example.

Parameters

from	Reference for which to get the relation

Returns: Iterator range [first,second) of elements which point from this object

Definition at line 160 of file RelationIndex.h.

◆ getElementsFrom() [2/2]

range_from getElementsFrom ( const FROM * from ) const

inline

Return a range of all elements pointing from the given object.

Can be used with range-based for, see RelationIndex class documentation for an example.

Parameters

from	Pointer for which to get the relation.

Returns: Iterator range [first,second) of elements which point from this object.

Definition at line 149 of file RelationIndex.h.

◆ getElementsTo() [1/2]

range_to getElementsTo ( const TO & to ) const

inline

Return a range of all elements pointing to the given object.

Can be used with range-based for, see RelationIndex class documentation for an example.

Parameters

to	Reference for which to get the relation

Returns: Iterator range [first,second) of elements which point to this object

Definition at line 182 of file RelationIndex.h.

◆ getElementsTo() [2/2]

range_to getElementsTo ( const TO * to ) const

inline

Return a range of all elements pointing to the given object.

Can be used with range-based for, see RelationIndex class documentation for an example.

Parameters

to	Pointer for which to get the relation

Returns: Iterator range [first,second) of elements which point to this object

Definition at line 171 of file RelationIndex.h.

◆ getFirstElementFrom() [1/2]

const Element* getFirstElementFrom ( const FROM & from ) const

inline

Return a pointer to the first relation Element of the given object.

Useful if there is at most one relation

Parameters

from	Reference for which to get the Relation

Returns: Pointer to the RelationIndex<FROM,TO>::Element, can be NULL if no relation exists

Definition at line 191 of file RelationIndex.h.

◆ getFirstElementFrom() [2/2]

const Element* getFirstElementFrom ( const FROM * from ) const

inline

Return a pointer to the first relation Element of the given object.

Useful if there is at most one relation

Parameters

from	Pointer for which to get the Relation

Returns: Pointer to the RelationIndex<FROM,TO>::Element, can be NULL if no relation exists

Definition at line 200 of file RelationIndex.h.

◆ getFirstElementTo() [1/2]

const Element* getFirstElementTo ( const TO & to ) const

inline

Return a pointer to the first relation Element of the given object.

Useful if there is at most one relation

Parameters

to	Reference for which to get the Relation

Returns: Pointer to the RelationIndex<FROM,TO>::Element, can be NULL if no relation exists

Definition at line 214 of file RelationIndex.h.

◆ getFirstElementTo() [2/2]

const Element* getFirstElementTo ( const TO * to ) const

inline

Return a pointer to the first relation Element of the given object.

Useful if there is at most one relation

Parameters

to	Pointer for which to get the Relation

Returns: Pointer to the RelationIndex<FROM,TO>::Element, can be NULL if no relation exists

Definition at line 223 of file RelationIndex.h.

The documentation for this class was generated from the following file:

framework/datastore/include/RelationIndex.h

Public Types

Public Member Functions

Protected Attributes

Detailed Description

template<class FROM, class TO> class Belle2::RelationIndex< FROM, TO >

Finding related objects

Member Typedef Documentation

◆ iterator_from

Constructor & Destructor Documentation

◆ RelationIndex() [1/2]

◆ RelationIndex() [2/2]

Member Function Documentation

◆ getElementsFrom() [1/2]

◆ getElementsFrom() [2/2]

◆ getElementsTo() [1/2]

◆ getElementsTo() [2/2]

◆ getFirstElementFrom() [1/2]

◆ getFirstElementFrom() [2/2]

◆ getFirstElementTo() [1/2]

◆ getFirstElementTo() [2/2]

template<class FROM, class TO>
class Belle2::RelationIndex< FROM, TO >