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Version: 1.6.1

Transformation modules C API

This is the additional API documentation for mg_procedure.h that contains declarations of all functions that can be used to implement a transformation. The source file can be found in the Memgraph installation directory, under include/memgraph. On the standard Debian installation, this will be under /usr/include/memgraph.

caution

NOTE: This part of the documentation is still under development. An updated version will soon be available.

Types#

Name
typedef void (*)(const struct mgp_messages *, const struct mgp_graph *, struct mgp_result *, struct mgp_memory *);mgp_trans_cb
Entry-point for a transformation with a fixed result type

Each record of the result must contain the following fields:

  • the query field with a Cypher query as a string that will be executed against the database
  • the parameters field with the optional query parameters as a nullable map

Functions#

Name
size_tmgp_messages_size(const struct mgp_messages *messages)
Get the number of messages contained in the messages list.
const struct mgp_message *mgp_messages_at(const struct mgp_messages *messages, size_t idx)
Get the mgp_message at index idx.
size_tmgp_message_payload_size(const struct mgp_message *message)
Get the payload size of message.
const char *mgp_message_payload(const struct mgp_message *message)
Get the payload of messages as a byte array.
const char *mgp_message_topic_name(const struct mgp_message *message)
Get the topic name of message.
size_tmgp_message_key_size(const struct mgp_message *message)
Get key size of message.
const char *mgp_message_key(const struct mgp_message *message)
Get key of message as a byte array.
int64_tmgp_message(const struct mgp_message *message)
Get the timestamp of message.
intmgp_module_add_transformation(struct mgp_module *module, const char *name, mgp_trans_cb cb)
Registers a transformation to a module

Types Documentation#

typedef mgp_trans_cb#

typedef void(* mgp_trans_cb) (const struct mgp_messages *, const struct mgp_graph *, struct mgp_result *, struct mgp_memory *);

Entry-point for a transformation invoked through a stream. Passed in arguments will not live longer than the callback's execution. Therefore, you must not store them globally or use the passed in mgp_memory to allocate global resources. The result type of transformation is fixed.

Functions Documentation#

function mgp_messages_size#

size_t mgp_messages_size(  const struct mgp_messages* messages)

Returns the total number of messages contained in the argument messages.

function mgp_messages_at#

mgp_message* mgp_messages_at(  const struct mgp_messages* messages,  size_t idx)

Accessor function that returns the underlying message stored at index idx in messages. The index supplied must reside in the half-open interval [0, mgp_messages_size(messages)).

function mgp_message_payload_size#

size_t mgp_message_payload_size  const struct mgp_message* message)

Returns the payload size of the argument message.

function mgp_message_payload#

const char * mgp_message_payload(  const struct mgp_message* message)

Returns the payload of the argument message as a byte array with size mgp_message_payload_size(message).

function mgp_message_topic_name#

const char * mgp_message_topic_name(  const struct mgp_message* message)

Returns topic name of the argument message. Topic name is NULL terminated.

function mgp_message_key_size#

size_t mgp_message_key_size(  const struct mgp_message* message)

Returns the key size of argument message.

function mgp_message_key#

const char * mgp_message_key(  const struct mgp_message* message)

Returns the key of the argument message as a byte array with size mgp_message_key_size(message).

function mgp_message_timestamp#

int64_t mgp_timestamp(  const struct mgp_message* message)

Returns the timestamp of the argument message.

function mgp_module_add_transformation#

int mgp_module_add_transformation(  struct mgp_module *module,  const char *name,  mgp_trans_cb cb)

Register a transformation to a module. The name must be a sequence of digits, underscores, lowercase, and uppercase Latin letters. The name must begin with a non-digit character. Note that Unicode characters are not allowed. Additionally, the name is case-sensitive.

Return non-zero if the transformation is added successfully. Registering might fail if unable to allocate memory for the transformation; if name is not valid, or a transformation with the same name was already registered or if any other unexpected failure happens.