knowrob::mongo::BindingsCursor Class Reference

#include <BindingsCursor.h>

Inheritance diagram for knowrob::mongo::BindingsCursor:

Collaboration diagram for knowrob::mongo::BindingsCursor:

Public Member Functions
	BindingsCursor (const std::shared_ptr< Collection > &collection)
bool	nextBindings (const std::shared_ptr< Bindings > &bindings)
	BindingsCursor (const std::shared_ptr< Collection > &collection)
bool	nextBindings (const std::shared_ptr< Bindings > &bindings)
Public Member Functions inherited from knowrob::mongo::Cursor
	Cursor (const std::shared_ptr< Collection > &collection)
	Cursor (const Cursor &)=delete
	~Cursor ()
const auto &	id ()
void	limit (unsigned int limit)
void	ascending (const char *key)
void	descending (const char *key)
void	filter (const bson_t *query_doc)
void	aggregate (const bson_t *query_doc)
bool	next (const bson_t **doc, bool ignore_empty=false)
bool	erase ()
const auto *	query () const
	Cursor (const std::shared_ptr< Collection > &collection)
	Cursor (const Cursor &)=delete
	~Cursor ()
const auto &	id ()
void	limit (unsigned int limit)
void	ascending (const char *key)
void	descending (const char *key)
void	filter (const bson_t *query_doc)
void	aggregate (const bson_t *query_doc)
bool	next (const bson_t **doc, bool ignore_empty=false)
bool	erase ()
const auto *	query () const

Protected Member Functions
void	setSubstitution (const std::shared_ptr< Bindings > &bindings)
void	setSubstitution (const std::shared_ptr< Bindings > &bindings)

Protected Attributes
const bson_t *	resultDocument_
bson_iter_t	resultIter_
bson_iter_t	varIter_
bson_iter_t	valIter_

Detailed Description

A Cursor that iterates over bindings computed through an aggregation pipeline which uses a special field in documents to store variable bindings throughout the pipeline.

Definition at line 18 of file BindingsCursor.h.

Constructor & Destructor Documentation

BindingsCursor() [1/2]

BindingsCursor::BindingsCursor ( const std::shared_ptr< Collection > &  collection )

explicit

Definition at line 17 of file BindingsCursor.cpp.

        : Cursor(collection),
          resultDocument_(nullptr),
          resultIter_(),
          varIter_(),
          valIter_() {
}

BindingsCursor() [2/2]

knowrob::mongo::BindingsCursor::BindingsCursor ( const std::shared_ptr< Collection > &  collection )

explicit

Member Function Documentation

nextBindings() [1/2]

bool BindingsCursor::nextBindings

(

const std::shared_ptr< Bindings > &

bindings

)

Parameters

bindings

the bindings to fill with the next result.

Returns

true if there is a next result, false otherwise.

Definition at line 73 of file BindingsCursor.cpp.

                                                                         {
    if (!next(&resultDocument_)) return false;
    if (!bson_iter_init(&resultIter_, resultDocument_)) return false;
 
    while (bson_iter_next(&resultIter_)) {
        std::string_view resultKey(bson_iter_key(&resultIter_));
        // read variables from "v_VARS". each sub-field is named according to the field of
        // a variable.
        if (resultKey == "v_VARS" && bson_iter_recurse(&resultIter_, &varIter_)) {
            setSubstitution(bindings);
        }
    }
 
    return true;
}

nextBindings() [2/2]

bool knowrob::mongo::BindingsCursor::nextBindings

(

const std::shared_ptr< Bindings > &

bindings

)

Parameters

bindings

the bindings to fill with the next result.

Returns

true if there is a next result, false otherwise.

setSubstitution() [1/2]

void BindingsCursor::setSubstitution ( const std::shared_ptr< Bindings > &  bindings )

protected

Definition at line 25 of file BindingsCursor.cpp.

                                                                            {
    while (bson_iter_next(&varIter_)) {
        auto var = std::make_shared<Variable>(bson_iter_key(&varIter_));
 
        if (!bson_iter_recurse(&varIter_, &valIter_)) continue;
        if (!bson_iter_find(&valIter_, "val")) continue;
 
        // read the value of the variable
        switch (bson_iter_type(&valIter_)) {
            case BSON_TYPE_UTF8: {
                auto utf8 = bson_iter_utf8(&valIter_, nullptr);
                // note: currently mongo KG does not store the type of the literal,
                // so we cannot trivially distinguish between IRI and literal and need to guess here.
                // note: we need to copy the string data here, as the bson_iter_utf8() returns a pointer
                // to the internal buffer of the bson document, which is not guaranteed to be valid
                // after the cursor is advanced.
                switch (rdfNodeTypeGuess(utf8)) {
                    case RDFNodeType::BLANK:
                        bindings->set(var, Blank::Tabled(utf8));
                        break;
                    case RDFNodeType::IRI:
                        bindings->set(var, IRIAtom::Tabled(utf8));
                        break;
                    case RDFNodeType::LITERAL:
                        bindings->set(var, std::make_shared<String>(utf8));
                        break;
                }
                break;
            }
            case BSON_TYPE_INT32:
                bindings->set(var, std::make_shared<Integer>(bson_iter_int32(&valIter_)));
                break;
            case BSON_TYPE_INT64:
                bindings->set(var, std::make_shared<Long>(bson_iter_int64(&valIter_)));
                break;
            case BSON_TYPE_BOOL:
                bindings->set(var, std::make_shared<Boolean>(bson_iter_bool(&valIter_)));
                break;
            case BSON_TYPE_DOUBLE:
                bindings->set(var, std::make_shared<Double>(bson_iter_double(&valIter_)));
                break;
            default:
                KB_WARN("unsupported type {} for predicate arguments.", bson_iter_type(&valIter_));
                break;
        }
    }
}

setSubstitution() [2/2]

void knowrob::mongo::BindingsCursor::setSubstitution ( const std::shared_ptr< Bindings > &  bindings )

protected

Member Data Documentation

resultDocument_

const bson_t * knowrob::mongo::BindingsCursor::resultDocument_

protected

Definition at line 29 of file BindingsCursor.h.

resultIter_

bson_iter_t knowrob::mongo::BindingsCursor::resultIter_

protected

Definition at line 30 of file BindingsCursor.h.

valIter_

bson_iter_t knowrob::mongo::BindingsCursor::valIter_

protected

Definition at line 32 of file BindingsCursor.h.

varIter_

bson_iter_t knowrob::mongo::BindingsCursor::varIter_

protected

Definition at line 31 of file BindingsCursor.h.

---

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

• build/_CPack_Packages/Linux/DEB/knowrob-2.1.0-Linux/usr/include/knowrob/storage/mongo/BindingsCursor.h
• src/storage/mongo/BindingsCursor.cpp