Query modules C++ API

This is the API documentation for mgp.hpp, which contains declarations of all functions in the C++ API for implementing query module procedures and functions. The source file can be found in the Memgraph installation directory, under /usr/include/memgraph.

To see how to implement query modules in C++, take a look at the example we provided.

If you install any C++ modules after running Memgraph, youll need to load them into Memgraph or restart Memgraph in order to use them.

Functions and procedures

With this API its possible to extend your Cypher queries with functions and procedures with AddProcedure and AddFunction.

The API needs memory access to add procedures and functions, this can be done with mgp::MemoryDispatcherGuard guard(memory);. Old code used mgp::memory = memory;, but this is not thread-safe and has been deprecated. v2.18.1 onwards you should modify your C++ modules and recompile. v2.21 onwards setting mgp::memory will cause a compilation error, so the guard has to be used.

Functions are simple operations that return a single value and can be used in any expression or predicate.

Procedures are more complex computations that may modify the graph, and their output is available to later processing steps in your query. A procedure may only be run from CALL clauses. The output is a stream of records that is made accessible with a YIELD clause.

AddProcedure

Add a procedure to your query module. The procedure is registered as [QUERY_MODULE_NAME].[PROC_NAME] and can be used in Cypher queries.

void AddProcedure(
    mgp_proc_cb callback,
    std::string_view name,
    ProcedureType proc_type,
    std::vector<Parameter> parameters,
    std::vector<Return> returns,
    mgp_module *module,
    mgp_memory *memory);

{

Input:

• callback: procedure callback
• name: procedure name
• proc_type: procedure type (read/write)
• parameters: vector (list) of procedure parameters
• returns: vector (list) of procedure return values
• module: the query module that the procedure is added to
• memory: access to memory

ProcedureType

Enum class for Cypher procedure types.

• ProcedureType::Read: read procedure
• ProcedureType::Write: write procedure

AddBatchProcedure

Add a batch procedure to your query module. The procedure is registered as [QUERY_MODULE_NAME].[PROC_NAME] and can be used in Cypher queries.

void AddBatchProcedure(
    mgp_proc_cb callback,
    mgp_proc_initializer initializer,
    mgp_proc_cleanup cleanup,
    std::string_view name,
    ProcedureType proc_type,
    std::vector<Parameter> parameters,
    std::vector<Return> returns,
    mgp_module *module,
    mgp_memory *memory);

{

Input:

• callback: procedure callback, invoked through OpenCypher
• initializer: procedure initializer, invoked before callback
• cleanup: procedure cleanup, invoked after batching is done
• name: procedure name
• proc_type: procedure type (read/write)
• parameters: vector (list) of procedure parameters
• returns: vector (list) of procedure return values
• module: the query module that the procedure is added to
• memory: access to memory

ProcedureType

Enum class for Cypher procedure types.

• ProcedureType::Read: read procedure
• ProcedureType::Write: write procedure

AddFunction

Add a function to your query module. The function is registered as [QUERY_MODULE_NAME].[FUNC_NAME] and can be used in Cypher queries.

void AddFunction(
    mgp_func_cb callback,
    std::string_view name,
    std::vector<Parameter> parameters,
    std::vector<Return> returns,
    mgp_module *module,
    mgp_memory *memory);

{

Input:

• callback: function callback
• name: function name
• parameters: vector (list) of function parameters
• returns: vector (list) of function return values
• module: the query module that the procedure is added to
• memory: access to memory

Parameter

Represents a procedure/function parameter. Parameters are defined by their name, type, and (if optional) default value.

Constructors

Creates a non-optional parameter with the given name and type.

Parameter(std::string_view name, Type type)

Creates an optional Boolean parameter with the given name and default_value.

Parameter(std::string_view name, Type type, bool default_value)

Creates an optional integer parameter with the given name and default_value.

Parameter(std::string_view name, Type type, int default_value)

Creates an optional floating-point parameter with the given name and default_value.

Parameter(std::string_view name, Type type, double default_value)

Creates an optional string parameter with the given name and default_value.

Parameter(std::string_view name, Type type, std::string_view default_value)
Parameter(std::string_view name, Type type, const char *default_value)

Creates a non-optional list parameter with the given name and item_type. The list_type parameter is organized as follows: {Type::List, Type::[ITEM_TYPE]}.

Parameter(std::string_view name, std::pair<Type, Type> list_type)

Creates an optional list parameter with the given name, item_type, and default_value. The list_type parameter is organized as follows: {Type::List, Type::[ITEM_TYPE]}.

Parameter(std::string_view name, std::pair<Type, Type> list_type, Value default_value)

Member variables

Return

Represents a procedure/function return value. Values are defined by their name and type.

Constructors

Creates a return value with the given name and type.

Return(std::string_view name, Type type)

Creates a return value with the given name and list_type. The list_type parameter is organized as follows: {Type::List, Type::[ITEM_TYPE]}.

Return(std::string_view name, std::pair<Type, Type> list_type)

Member variables

RecordFactory

Factory class for Record.

Constructors

explicit RecordFactory(mgp_result *result)

Member functions

NewRecord

Adds a new result record.

  Record NewRecord() const

SetErrorMessage

Sets the given error message.

  void SetErrorMessage(std::string_view error_msg) const

  void SetErrorMessage(const char *error_msg) const

Record

Represents a record - the building block of Cypher procedure results. Each result is a stream of records, and a functions record is a sequence of (field name: output value) pairs.

Constructors

explicit Record(mgp_result_record *record)

Member functions

Insert

Inserts a value of given type under field field_name.

  void Insert(const char *field_name, bool value)

  void Insert(const char *field_name, std::int64_t value)

  void Insert(const char *field_name, double value)

  void Insert(const char *field_name, std::string_view value)

  void Insert(const char *field_name, const char *value)

  void Insert(const char *field_name, const List &value)

  void Insert(const char *field_name, const Map &value)

  void Insert(const char *field_name, const Node &value)

  void Insert(const char *field_name, const Relationship &value)

  void Insert(const char *field_name, const Path &value)

  void Insert(const char *field_name, const Date &value)

  void Insert(const char *field_name, const LocalTime value)

  void Insert(const char *field_name, const LocalDateTime value)

  void Insert(const char *field_name, const ZonedDateTime value)

  void Insert(const char *field_name, const Duration value)

  void Insert(const char *field_name, const Point2d &value)

  void Insert(const char *field_name, const Point3d &value)

  void Insert(const char *field_name, const Enum &value)

  void Insert(const char *field_name, const Value &value)

Result

Represents a result - the single return value of a Cypher function.

Constructors

explicit Result(mgp_func_result *result)

Member functions

SetValue

Sets a return value of given type.

  void SetValue(bool value)

  void SetValue(std::int64_t value)

  void SetValue(double value)

  void SetValue(std::string_view value)

  void SetValue(const char *value)

  void SetValue(const List &value)

  void SetValue(List &&value)

  void SetValue(const Map &value)

  void SetValue(Map &&value)

  void SetValue(const Node &value)

  void SetValue(const Relationship &value)

  void SetValue(const Path &value)

  void SetValue(const Date &value)

  void SetValue(const LocalTime &value)

  void SetValue(const LocalDateTime &value)

  void SetValue(const ZonedDateTime &value)

  void SetValue(const Duration &value)

  void SetValue(const Point2d &value)

  void SetValue(const Point3d &value)

  void SetValue(const Enum &value)

  void SetValue(const Value &value)

SetErrorMessage

Sets the given error message.

  void SetErrorMessage(std::string_view error_msg) const

  void SetErrorMessage(const char *error_msg) const

Graph API

This section covers the interface for working with the Memgraph DB graph using the C++ API. A description of data types is available in the reference guide.

Graph

Constructors

explicit Graph(mgp_graph *graph)

Member functions

Order

Returns the graph order (number of nodes).

int64_t Order() const

Size

Returns the graph size (number of relationships).

int64_t Size() const

Nodes (GraphNodes)

Returns an iterable structure of the graphs nodes.

GraphNodes Nodes() const

Relationships

Returns an iterable structure of the graphs relationships.

GraphRelationships Relationships() const

GetNodeById

Returns the graph node with the given ID.

Node GetNodeById(Id node_id) const

ContainsNode

Returns whether the graph contains a node with the given ID.

bool ContainsNode(Id node_id) const

Returns whether the graph contains the given node.

bool ContainsNode(const Node &node) const

ContainsRelationship

bool ContainsRelationship(Id relationship_id) const

bool ContainsRelationship(const Relationship &relationship) const

IsMutable

Returns whether the graph is mutable.

bool IsMutable() const

IsTransactional

Returns whether the graph is in a transactional storage mode.

bool IsTransactional() const

CreateNode

Creates a node and adds it to the graph.

Node CreateNode();

DeleteNode

Deletes a node from the graph.

void DeleteNode(const Node &node)

DetachDeleteNode

Deletes a node and all its incident edges from the graph.

void DetachDeleteNode(const Node &node)

CreateRelationship

Creates a relationship of type type between nodes from and to and adds it to the graph.

Relationship CreateRelationship(const Node &from, const Node &to, std::string_view type)

DeleteRelationship

Deletes a relationship from the graph.

void DeleteRelationship(const Relationship &relationship)

SetFrom

Changes the from (start) node of the given relationship.

void SetFrom(Relationship &relationship, const Node &new_from)

SetTo

Changes the to (end) node of the given relationship.

void SetTo(Relationship &relationship, const Node &set_to)

ChangeType

Changes the relationship type

void ChangeType(Relationship &relationship, std::string_view new_type);

GraphNodes

Auxiliary class providing an iterable view of the nodes contained in the graph. GraphNodes values may only be used for iteration to obtain the values stored within.

Constructors

explicit GraphNodes(mgp_vertices_iterator *nodes_iterator)

Member variables

Member functions

GraphRelationships

Auxiliary class providing an iterable view of the relationships contained in the graph. GraphRelationships values may only be used for iteration to obtain the values stored within.

Constructors

explicit GraphRelationships(mgp_graph *graph)

Member variables

Member functions

Node

Represents a node (vertex) of the Memgraph graph.

Constructors

Creates a Node from the copy of the given mgp_vertex.

explicit Node(mgp_vertex *ptr)
explicit Node(const mgp_vertex *const_ptr)

Copy and move constructors:

Node(const Node &other)
Node(Node &&other) noexcept

Member functions

IsDeleted

Returns whether the node has been deleted.

bool IsDeleted() const

Id

Returns the nodes ID.

mgp::Id Id() const

Labels

Returns an iterable & indexable structure of the nodes labels.

class Labels Labels() const

HasLabel

Returns whether the node has the given label.

bool HasLabel(std::string_view label) const

Properties

Returns an iterable & indexable structure of the nodes properties.

std::unordered_map<std::string, mgp::Value> Properties() const

GetProperty

Gets value of nodes property.

mgp::value GetProperty(const std::string& property) const

SetProperty

Sets the value of the nodes property.

void SetProperty(std::string key, std::string value)

SetProperties

Updates the nodes properties with the given map.

void SetProperties(std::unordered_map<std::string_view, Value> properties)

RemoveProperty

Removes the nodes property.

void RemoveProperty(std::string property)

InRelationships

Returns an iterable structure of the nodes inbound relationships.

Relationships InRelationships() const

OutRelationships

Returns an iterable structure of the nodes outbound relationships.

Relationships OutRelationships() const

AddLabel

Adds a label to the node.

void AddLabel(std::string_view label)

RemoveLabel

Removes a label from a node.

void RemoveLabel(std::string_view label)

InDegree

Returns the in degree of a node.

size_t InDegree() const

OutDegree

Returns the out degree of a node.

size_t OutDegree() const

ToString

Returns the nodes string representation, which has this format: (id: node_id, labels: node_labels, properties: node_properties_map).

std::string ToString() const

Operators

operator[]

Returns the value of the nodes property_name property.

Value operator[](std::string_view property_name) const

Relationship

Represents a relationship (edge) of the Memgraph graph.

Constructors

Creates a Relationship from the copy of the given mgp_edge.

explicit Relationship(mgp_edge *ptr)
explicit Relationship(const mgp_edge *const_ptr)

Copy and move constructors:

Relationship(const Relationship &other)
Relationship(Relationship &&other) noexcept

Member functions

IsDeleted

Returns whether the relationship has been deleted.

bool IsDeleted() const

Id

Returns the relationships ID.

mgp::Id Id() const

Type

Returns the relationships type.

std::string_view Type() const

Properties

Returns an iterable & indexable structure of the relationships properties.

std::unordered_map<std::string, mgp::Value> Properties() const

GetProperty

Gets value of the relationships property.

mgp::value GetProperty(const std::string& property) const

SetProperty

Sets the value of the relationships property.

void SetProperty(std::string key, std::string value)

SetProperties

Updates the relationships properties with the given map.

void SetProperties(std::unordered_map<std::string_view, Value> properties)

RemoveProperty

Removes the relationships property.

void RemoveProperty(std::string property)

From

Returns the relationships source node.

Node From() const

To

Returns the relationships source node.

Node To() const

ToString

Returns the relationships string representation, which has this format: (node_from.ToString())-(type: relationship_type, id: relationship_id, properties: relationship_properties_map)->(node_to.ToString()).

std::string ToString() const

Operators

operator[]

Returns the value of the relationships property_name property.

Value operator[](std::string_view property_name) const

Object is hashable using

std::hash<mgp::Relationship>

Relationships

Auxiliary class providing an iterable view of the relationships adjacent to a node. Relationships values may only be used for iteration to obtain the values stored within.

Constructors

explicit Relationships(mgp_edges_iterator *relationships_iterator)

Member variables

Member functions

Id

Represents the unique ID possessed by all Memgraph nodes and relationships.

Member functions

FromUint

Constructs an Id object from uint64_t.

static Id FromUint(uint64_t id)

FromInt

Constructs an Id object from int64_t.

static Id FromInt(int64_t id)

AsUint

Returns the ID value as uint64_t.

int64_t AsUint() const

AsInt

Returns the ID value as int64_t.

int64_t AsInt() const

Operators

Labels

Represents a view of node labels.

Constructors

explicit Labels(mgp_vertex *node_ptr)

Copy and move constructors:

Labels(const Labels &other)
Labels(Labels &&other) noexcept

Member variables

Member functions

Size

Returns the number of the labels, i.e. the size of their list.

size_t Size() const

Operators

operator[]

Returns the nodes label at position index.

std::string_view operator[](size_t index) const

Date

Represents a date with a year, month, and day.

Constructors

Creates a Date object from the copy of the given mgp_date.

explicit Date(mgp_date *ptr)
explicit Date(const mgp_date *const_ptr)

Creates a Date object from the given string representing a date in the ISO 8601 format (YYYY-MM-DD, YYYYMMDD, or YYYY-MM).

explicit Date(std::string_view string)

Creates a Date object with the given year, month, and day properties.

Date(int year, int month, int day)

Copy and move constructors:

Date(const Date &other)
Date(Date &&other) noexcept

Member functions

Now

Returns the current Date.

static Date Now()

Year

Returns the dates year property.

int Year() const

Month

Returns the dates month property.

int Month() const

Day

Returns the dates day property.

int Day() const

Timestamp

Returns the dates timestamp (microseconds since Unix epoch).

int64_t Timestamp() const

ToString

Returns the dates string representation, which has this format: year-month-day.

std::string ToString() const

Operators

operator-

Date operator-(const Duration &dur) const

Duration operator-(const Date &other) const

operator[]

Returns the value of the relationships property_name property.

Value operator[](std::string_view property_name) const

Object is hashable using

std::hash<mgp::Date>

LocalTime

Represents a time within the day without timezone information.

Constructors

Creates a LocalTime object from the copy of the given mgp_local_time.

explicit LocalTime(mgp_local_time *ptr)
explicit LocalTime(const mgp_local_time *const_ptr)

Creates a LocalTime object from the given string representing a date in the ISO 8601 format ([T]hh:mm:ss, [T]hh:mm, [T]hhmmss, [T]hhmm, or [T]hh).

explicit LocalTime(std::string_view string)

Creates a LocalTime object with the given hour, minute, second, millisecond, and microsecond properties.

LocalTime(int hour, int minute, int second, int millisecond, int microsecond)

Copy and move constructors:

LocalTime(const LocalTime &other)
LocalTime(LocalTime &&other) noexcept

Member functions

Now

Returns the current LocalTime.

static LocalTime Now()

Hour

Returns the objects hour property.

int Hour() const

Minute

Returns the objects minute property.

int Minute() const

Second

Returns the objects second property.

int Second() const

Millisecond

Returns the objects millisecond property.

int Millisecond() const

Microsecond

Returns the objects microsecond property.

int Microsecond() const

Timestamp

Returns the objects timestamp (microseconds since Unix epoch).

int64_t Timestamp() const

ToString

Returns the objects string representation, which has this format: hour:minute:second,microsecond milisecond.

std::string ToString() const

Operators

operator-

LocalTime operator-(const Duration &dur) const

Duration operator-(const LocalDateTime &other) const

Object is hashable using

std::hash<mgp::LocalTime>

LocalDateTime

Temporal type representing a date and a local time.

Constructors

Creates a LocalDateTime object from the copy of the given mgp_local_date_time.

explicit LocalDateTime(mgp_local_date_time *ptr)
explicit LocalDateTime(const mgp_local_date_time *const_ptr)

Creates a LocalDateTime object from the given string representing a date in the ISO 8601 format (YYYY-MM-DDThh:mm:ss, YYYY-MM-DDThh:mm, YYYYMMDDThhmmss, YYYYMMDDThhmm, or YYYYMMDDThh).

explicit LocalDateTime(std::string_view string)

Creates a LocalDateTime object with the given year, month, day, hour, minute, second, millisecond, and microsecond properties.

LocalDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int microsecond)

Copy and move constructors:

LocalDateTime(const LocalDateTime &other)
LocalDateTime(LocalDateTime &&other) noexcept

Member functions

Now

Returns the current LocalDateTime.

static LocalDateTime Now()

Year

Returns the objects year property.

int Year() const

Month

Returns the objects month property.

int Month() const

Day

Returns the objects day property.

int Day() const

Hour

Returns the objects hour property.

int Hour() const

Minute

Returns the objects minute property.

int Minute() const

Second

Returns the objects second property.

int Second() const

Millisecond

Returns the objects millisecond property.

int Millisecond() const

Microsecond

Returns the objects microsecond property.

int Microsecond() const

Timestamp

Returns the dates timestamp (microseconds since Unix epoch).

int64_t Timestamp() const

ToString

Returns the objects string representation, which has this format: year-month-dayThour:minute:second,microsecond milisecond.

std::string ToString() const

Operators

operator-

LocalDateTime operator-(const Duration &dur) const

Duration operator-(const LocalDateTime &other) const

Object is hashable using

std::hash<mgp::LocalDateTime>

ZonedDateTime

Temporal type representing a date-time with timezone information.

Constructors

Creates a ZonedDateTime object from the copy of the given mgp_zoned_date_time.

explicit ZonedDateTime(mgp_zoned_date_time *ptr)
explicit ZonedDateTime(const mgp_zoned_date_time *const_ptr)

Creates a ZonedDateTime object from the given string representing a date in the ISO 8601 format (YYYY-MM-DDThh:mm:ss, YYYY-MM-DDThh:mm, YYYYMMDDThhmmss, YYYYMMDDThhmm, or YYYYMMDDThh). The string can also include timezone information as a numeric offset (+HH:MM or -HH:MM) or a named timezone identifier ([America/New_York]).

explicit ZonedDateTime(std::string_view string)

Creates a ZonedDateTime object with the given year, month, day, hour, minute, second, millisecond, microsecond, and offset_in_minutes properties.

ZonedDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int microsecond,
              int offset_in_minutes)

Creates a ZonedDateTime object with the given year, month, day, hour, minute, second, millisecond, microsecond, and timezone_name properties.

ZonedDateTime(int year, int month, int day, int hour, int minute, int second, int millisecond, int microsecond,
              std::string_view timezone_name)

ZonedDateTime(const ZonedDateTime &other)
ZonedDateTime(ZonedDateTime &&other) noexcept

Member functions

Now

Returns the current ZonedDateTime.

static ZonedDateTime Now()

Year

Returns the objects year property.

int Year() const

Month

Returns the objects month property.

int Month() const

Day

Returns the objects day property.

int Day() const

Hour

Returns the objects hour property.

int Hour() const

Minute

Returns the objects minute property.

int Minute() const

Second

Returns the objects second property.

int Second() const

Millisecond

Returns the objects millisecond property.

int Millisecond() const

Microsecond

Returns the objects microsecond property.

int Microsecond() const

Timezone

Returns the objects timezone string property.

char const *Timezone() const

Offset

Returns the objects offset property.

int Offset() const

Timestamp

Returns the objects timestamp (microseconds from Unix epoch).

int64_t Timestamp() const

ToString

Returns the objects string representation.

std::string ToString() const

Operators

operator-

ZonedDateTime operator-(const Duration &dur) const

Duration operator-(const ZonedDateTime &other) const

Object is hashable using

std::hash<mgp::ZonedDateTime>

Duration

Represents a period of time in Memgraph.

Constructors

Creates a Duration object from the copy of the given mgp_duration.

explicit Duration(mgp_duration *ptr)
explicit Duration(const mgp_duration *const_ptr)

Creates a Duration object from the given string in the following format: P[nD]T[nH][nM][nS], where (1) n stands for a number, (2) capital letters are used as a separator, (3) each field in [] is optional, and (4) only the last field may be a non-integer.

explicit Duration(std::string_view string)

Creates a Duration object from the given number of microseconds.

explicit Duration(int64_t microseconds)

Creates a Duration object with the given day, hour, minute, second, millisecond, and microsecond properties.

Duration(double day, double hour, double minute, double second, double millisecond, double microsecond)

Copy and move constructors:

Duration(const Duration &other)
Duration(Duration &&other) noexcept

Member functions

Microseconds

Returns the duration as microseconds.

int64_t Microseconds() const

ToString

Returns the durations string representation, which has this format: microseconds ms.

std::string ToString() const

Operators

operator-

Duration operator-(const Duration &other) const

Duration operator-() const

Object is hashable using

std::hash<mgp::Duration>

Point2d

Represents a 2D point with x and y coordinates and a spatial reference identifier (SRID).

Constructors

Creates a Point2d object from the copy of the given mgp_point_2d.

explicit Point2d(mgp_point_2d *ptr)
explicit Point2d(const mgp_point_2d *const_ptr)

Creates a Point2d object with the given x, y coordinates and srid.

Point2d(double x, double y, uint16_t srid)

Supported SRIDs: 4326 (WGS-84), 7203 (Cartesian 2D).

Copy and move constructors:

Point2d(const Point2d &other)
Point2d(Point2d &&other) noexcept

Member functions

X

Returns the x coordinate of the point.

double X() const

Y

Returns the y coordinate of the point.

double Y() const

Srid

Returns the SRID (spatial reference identifier) of the point.

uint16_t Srid() const

ToString

Returns the points string representation.

std::string ToString() const

Operators

Object is hashable using

std::hash<mgp::Point2d>

Point3d

Represents a 3D point with x, y, and z coordinates and a spatial reference identifier (SRID).

Constructors

Creates a Point3d object from the copy of the given mgp_point_3d.

explicit Point3d(mgp_point_3d *ptr)
explicit Point3d(const mgp_point_3d *const_ptr)

Creates a Point3d object with the given x, y, z coordinates and srid.

Point3d(double x, double y, double z, uint16_t srid)

Supported SRIDs: 4979 (WGS-84 3D), 9157 (Cartesian 3D).

Copy and move constructors:

Point3d(const Point3d &other)
Point3d(Point3d &&other) noexcept

Member functions

X

Returns the x coordinate of the point.

double X() const

Y

Returns the y coordinate of the point.

double Y() const

Z

Returns the z coordinate of the point.

double Z() const

Srid

Returns the SRID (spatial reference identifier) of the point.

uint16_t Srid() const

ToString

Returns the points string representation.

std::string ToString() const

Operators

Object is hashable using

std::hash<mgp::Point3d>

Enum

Represents an enum value with a type name and value name.

Note: Enum values can be received as procedure input and inspected (type name, value name, equality), but cannot be returned from procedures.

Constructors

Creates an Enum object from the copy of the given mgp_enum.

explicit Enum(mgp_enum *ptr)
explicit Enum(const mgp_enum *const_ptr)

Creates an Enum from type name and value name strings.

Enum(std::string_view type_name, std::string_view value_name)

Copy and move constructors:

Enum(const Enum &other)
Enum(Enum &&other) noexcept

Member functions

TypeName

Returns the type name of the enum (e.g. "Status" for Status.Active).

std::string_view TypeName() const

ValueName

Returns the value name of the enum (e.g. "Active" for Status.Active).

std::string_view ValueName() const

ToString

Returns the enums string representation.

std::string ToString() const

Operators

Object is hashable using

std::hash<mgp::Enum>

Path

A path is a data structure consisting of alternating nodes and relationships, with the start and end points of a path necessarily being nodes.

Constructors

Creates a Path from the copy of the given mgp_path.

explicit Path(mgp_path *ptr)
explicit Path(const mgp_path *const_ptr)

Creates a Path starting with the given start_node.

explicit Path(const Node &start_node)

Copy and move constructors:

Path(const Path &other)
Path(Path &&other) noexcept

Member functions

ContainsDeleted

Returns whether the path contains any deleted nodes or relationships.

bool ContainsDeleted() const

Length

Returns the path length (number of relationships).

size_t Length() const

GetNodeAt

Returns the node at the given index. The index must be less than or equal to length of the path.

Node GetNodeAt(size_t index) const

GetRelationshipAt

Returns the relationship at the given index. The index must be less than the length of the path.

Relationship GetRelationshipAt(size_t index) const

Expand

Adds a relationship continuing from the last node on the path.

void Expand(const Relationship &relationship)

Pop

Removes the last node and the last relationship from the path.

void Pop()

ToString

Returns the paths string representation, which has nearly the same format as Relationship.ToString(), the difference being that Path.ToString() can have multiple nodes and relationships in its string representation, for example: (node)-(relationship)->(node)-(relationship)->(node).

std::string ToString() const

Operators

Object is hashable using

std::hash<mgp::Path>

List

A list containing any number of values of any supported type.

Constructors

Creates a List from the copy of the given mgp_list.

explicit List(mgp_list *ptr)
explicit List(const mgp_list *const_ptr)

Creates an empty List.

explicit List()

Creates a List with the given capacity.

explicit List(size_t capacity)

Creates a List from the given vector.

explicit List(const std::vector<Value> &values)
explicit List(std::vector<Value> &&values)

Creates a List from the given initializer_list.

explicit List(std::initializer_list<Value> list)

Copy and move constructors:

List(const List &other)
List(List &&other) noexcept

Member variables

Member functions

ContainsDeleted

Returns whether the path contains any deleted values (Node, Relationship, or containers holding them).

bool ContainsDeleted() const

Size

Returns the size of the list.

size_t Size() const

Empty

Returns whether the list is empty.

bool Empty() const

Append

Appends the given value to the list. The value is copied.

void Append(const Value &value)

AppendExtend

Extends the list and appends the given value to it. The value is copied.

void AppendExtend(const Value &value)

ToString

Returns the lists string representation, which has this format: [element.ToString(), element.ToString()].

std::string ToString() const

Operators

operator[]

Returns the reference of the value at the given index.

Value operator[](size_t index) const

Object is hashable using

std::hash<mgp::List>

Map

A map of key-value pairs where keys are strings, and values can be of any supported type. The pairs are represented as MapItems.

Constructors

Creates a Map from the copy of the given mgp_map.

explicit Map(mgp_map *ptr)
explicit Map(const mgp_map *const_ptr)

Creates an empty Map.

explicit Map()

Creates a Map from the given STL map.

explicit Map(const std::map<std::string_view, Value> &items)
explicit Map(std::map<std::string_view, Value> &&items)

Creates a Map from the given initializer_list (map items correspond to initializer list pairs).

Map(std::initializer_list<std::pair<std::string_view, Value>> items)

Copy and move constructors:

Map(const Map &other)
Map(Map &&other) noexcept

Member variables

Member functions

ContainsDeleted

Returns whether the path contains any deleted values (Node, Relationship, or containers holding them).

bool ContainsDeleted() const

Size

Returns the size of the map.

size_t Size() const

Empty

Returns whether the map is empty.

bool Empty() const

At

Returns the value at the given key.

Value At(std::string_view key) const

Insert

Inserts the given key-value pair into the map. The value is copied.

void Insert(std::string_view key, const Value &value)

Inserts the given key-value pair into the map. Takes ownership of value by moving it. The behavior of accessing value after performing this operation is undefined.

void Insert(std::string_view key, Value &&value)

Update

Updates the key-value pair in the map. If the key doesnt exist, the value gets inserted. The value is copied.

void Update(std::string_view key, const Value &value)

Updates the key-value pair in the map. If the key doesnt exist, the value gets inserted. The value is copied. Takes the ownership of value by moving it. The behavior of accessing value after performing this operation is undefined.

void Update(std::string_view key, Value &&value)

Erase

Erases the element associated with the key from the map, if it doesnt exist nothing happens.

void Erase(std::string_view key);

ToString

Returns the maps string representation, which has this format: {key1 : value1.ToString(), key2: value2.ToString()}.

std::string ToString() const

KeyExists

Returns true if key is present in the map, otherwise false.

bool KeyExists(std::string_view key) const;

Operators

operator[]

Returns the reference of the value at the given key.

Value operator[](std::string_view key) const

Object is hashable using

std::hash<mgp::Map>

MapItem

Auxiliary data structure representing key-value pairs where keys are strings, and values can be of any supported type.

Member variables

Operators

Object is hashable using

std::hash<mgp::MapItem>

Value

Represents a value of any type supported by Memgraph. The data types are described in the reference guide.

Constructors

Creates a Value from the copy of the given mgp_value.

explicit Value(mgp_value *ptr)

Create a reference type Value

explicit Value(RefType /**/, mgp_value *ptr)

Create a reference type Value

explicit Value(RefType /**/, mgp_value *ptr)

Create a Value by moving the given mgp_value ptr

explicit Value(StealType /**/, mgp_value *ptr)

Creates a null Value.

explicit Value()

Basic type constructors:

explicit Value(bool value)
explicit Value(int64_t value)
explicit Value(double value)
explicit Value(const char *value)
explicit Value(std::string_view value)

Container type constructors:

explicit Value(const List &value)
explicit Value(List &&value)
explicit Value(const Map &value)
explicit Value(Map &&value)

Graph element type constructors:

explicit Value(const Node &value)
explicit Value(Node &&value)
explicit Value(const Relationship &value)
explicit Value(Relationship &&value)
explicit Value(const Path &value)
explicit Value(Path &&value)

Temporal type constructors:

explicit Value(const Date &value)
explicit Value(Date &&value)
explicit Value(const LocalTime &value)
explicit Value(LocalTime &&value)
explicit Value(const LocalDateTime &value)
explicit Value(LocalDateTime &&value)
explicit Value(const ZonedDateTime &value)
explicit Value(ZonedDateTime &&value)
explicit Value(const Duration &value)
explicit Value(Duration &&value)

Spatial type constructors:

explicit Value(const Point2d &value)
explicit Value(Point2d &&value)
explicit Value(const Point3d &value)
explicit Value(Point3d &&value)

Enum type constructors:

explicit Value(const Enum &value)
explicit Value(Enum &&value)

Copy and move constructors:

Value(const Value &other)
Value(Value &&other) noexcept

Member functions

Type

Returns the C API pointer to the stored value.

mgp_value *ptr() const

Type

Returns the type of the value, i.e. the type stored in the Value object.

mgp::Type Type() const

Value[TYPE]

Depending on the exact function called, returns a typed value of the appropriate type. Throws an exception if the type stored in the Value object is not compatible with the function called. An overloaded function is available which returns a modifiable (non-const) value of the appropriate type.

bool ValueBool() const
bool ValueBool()

int64_t ValueInt() const
int64_t ValueInt()

double ValueDouble const
double ValueDouble

double ValueNumeric const
double ValueNumeric

std::string_view ValueString() const
std::string_view ValueString()

List ValueList() const
List ValueList()

Map ValueMap() const
Map ValueMap()

Node ValueNode() const
Node ValueNode()

Relationship ValueRelationship() const
Relationship ValueRelationship()

Path ValuePath() const
Path ValuePath()

Date ValueDate() const
Date ValueDate()

LocalTime ValueLocalTime() const
LocalTime ValueLocalTime()

LocalDateTime ValueLocalDateTime() const
LocalDateTime ValueLocalDateTime()

ZonedDateTime ValueZonedDateTime() const
ZonedDateTime ValueZonedDateTime()

Duration ValueDuration() const
Duration ValueDuration()

Point2d ValuePoint2d() const
Point2d ValuePoint2d()