mongoc_collection_command()#

Warning

Deprecated since version 1.29.0: This function is deprecated and should not be used in new code. Use mongoc_collection_command_simple() instead.

Synopsis#

mongoc_cursor_t *
mongoc_collection_command (mongoc_collection_t *collection,
                           mongoc_query_flags_t flags,
                           uint32_t skip,
                           uint32_t limit,
                           uint32_t batch_size,
                           const bson_t *command,
                           const bson_t *fields,
                           const mongoc_read_prefs_t *read_prefs);

This function is not considered a retryable read operation.

Parameters#

  • collection: A mongoc_collection_t.

  • flags: Unused.

  • skip: Unused.

  • limit: Unused.

  • batch_size: Unused.

  • command: A bson_t containing the command to execute.

  • fields: Unused.

  • read_prefs: An optional mongoc_read_prefs_t. Otherwise, the command uses mode MONGOC_READ_PRIMARY.

Migrating#

mongoc_collection_command() is deprecated.

The following example uses mongoc_collection_command():

Before#
const bson_t *reply;
bson_t *cmd = BCON_NEW ("find", "foo", "filter", "{", "}");
mongoc_cursor_t *cursor = mongoc_collection_command (coll,
                                                     MONGOC_QUERY_NONE /* unused */,
                                                     0 /* unused */,
                                                     0 /* unused */,
                                                     0 /* unused */,
                                                     cmd,
                                                     NULL /* unused */,
                                                     NULL /* read prefs */);
// Expect cursor to return exactly one document for the command reply.
EXPECT (mongoc_cursor_next (cursor, &reply));

bson_error_t error;
if (mongoc_cursor_error (cursor, &error)) {
   FAIL ("Expected no error, got: %s\n", error.message);
}

// Expect successful reply to contain "ok": 1
bson_iter_t iter;
EXPECT (bson_iter_init_find (&iter, reply, "ok") && bson_iter_as_int64 (&iter) == 1);

// Expect cursor to return no other documents.
EXPECT (!mongoc_cursor_next (cursor, &reply));
mongoc_cursor_destroy (cursor);
bson_destroy (cmd);

The above code block may be rewritten to use mongoc_collection_command_simple() instead, as shown below:

After#
bson_t reply;
bson_error_t error;
bson_t *cmd = BCON_NEW ("find", "foo", "filter", "{", "}");
if (!mongoc_collection_command_simple (coll, cmd, NULL /* read prefs */, &reply, &error)) {
   FAIL ("Expected no error, got: %s\n", error.message);
}

// Expect successful reply to contain "ok": 1
bson_iter_t iter;
EXPECT (bson_iter_init_find (&iter, &reply, "ok") && bson_iter_as_int64 (&iter) == 1);

bson_destroy (&reply);
bson_destroy (cmd);

Returns#

This function returns a newly allocated mongoc_cursor_t that should be freed with mongoc_cursor_destroy() when no longer in use. The returned mongoc_cursor_t is never NULL, even on error. The user must call mongoc_cursor_next() on the returned mongoc_cursor_t to execute the initial command.

Cursor errors can be checked with mongoc_cursor_error_document(). It always fills out the bson_error_t if an error occurred, and optionally includes a server reply document if the error occurred server-side.

Warning

Failure to handle the result of this function is a programming error.