MONGOC_DATABASE_COMMAND(3)

💅 MONGOC_DATABASE_COMMAND(3) — bestie edition ✨

okay so before we even get into it — this one lives in libmongoc, and it's the database-level command cursor thing. Sit down, hydrate, let's go 🫶

---

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

Like, she still works, but she's on her way out. New code should NOT be caught using her. Periodt 💀

---

✨ SYNOPSIS ✨

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);

---

🦋 DESCRIPTION 🦋

So basically this function builds you a cursor that will actually run the command when you call mongoc_cursor_next() on it. Not before. It's giving "I'll do it when you ask me to" energy 😌

Important tea though: 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 a write concern timeout. So don't come crying to her about write concern, she didn't sign up for that.

Also — this function is not considered a retryable read operation. No cap.

---

🎀 PARAMETERS 🎀

• database — A mongoc_database_t. The main character here obviously 👑
• flags — Unused. Literally just sitting there. Ignore her.
• skip — Unused. Bestie, leave it alone.
• limit — Unused. Don't even look at it.
• batch_size — Unused. She's decorative, that's the vibe 💅
• command — A bson_t containing the command. This one actually matters ✨
• fields — Unused. Just vibes.
• read_prefs — An optional mongoc_read_prefs_t. If you don't pass one, the command uses mode MONGOC_READ_PRIMARY.

---

🌈 MIGRATING 🌈

mongoc_database_command() is deprecated. Yeah. So here's the glow-up tutorial, before-and-after style 😭

Here's the example that 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);

See? The glow-up is real. Same energy, way fewer unused params 🧚

---

💖 RETURNS 💖

This function returns a newly allocated mongoc_cursor_t that you should free with mongoc_cursor_destroy() when you're done with it — no leaving her on read, okay?

The returned mongoc_cursor_t is never NULL, even on error. That's right, even when everything's a mess she still shows up 🙈

And the user must call mongoc_cursor_next() on the returned mongoc_cursor_t to execute the initial command. It doesn't run itself, bestie, that's on you.

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. So thorough of her 💅

⚠️ WARNING: Failure to handle the result of this function is a programming error. Like fr fr, handle your results. Don't be that girl.

---

🌟 AUTHOR 🌟

MongoDB, Inc

---

👑 COPYRIGHT 👑

2009-present, MongoDB, Inc.

---

and that's the whole page, bestie! ✨ This was libmongoc version 1.30.13, dated Oct 09, 2026, and yeah — the man page said MONGOC_DATABASE_COMMAND(3) at the top and at the bottom, we said it twice, iconic behavior 💅💖