mongoc_database_command - Man Page

mongoc_cursor_t *
mongoc_database_command (mongoc_database_t *database,
                         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 creates a cursor which will execute the command when mongoc_cursor_next() <> is called on it. The database's read preference, read concern, and write concern are not applied to the command, and mongoc_cursor_next() <> will not check the server response for a write concern error or write concern timeout.

This function is not considered a retryable read operation.

• database: A mongoc_database_t <>.
• flags: Unused.
• skip: Unused.
• limit: Unused.
• batch_size: Unused.
• command: A bson_t <https://www.mongoc.org/libbson/current/bson_t.html> containing the command.
• fields: Unused.
• read_prefs: An optional mongoc_read_prefs_t <>. Otherwise, the command uses mode MONGOC_READ_PRIMARY.

mongoc_database_command() <> is deprecated.

The following example uses mongoc_database_command() <>:

Before

const bson_t *reply;
bson_t *cmd = BCON_NEW ("find", "foo", "filter", "{", "}");
mongoc_cursor_t *cursor = mongoc_database_command (db,
                                                   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_database_command_simple() <> instead, as shown below:

After

bson_t reply;
bson_error_t error;
bson_t *cmd = BCON_NEW ("find", "foo", "filter", "{", "}");
if (!mongoc_database_command_simple (db, 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);

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 <https://www.mongoc.org/libbson/current/bson_error_t.html> if an error occurred, and optionally includes a server reply document if the error occurred server-side.

Warning:

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