mongoc_collection_command_simple()

Synopsis

bool
mongoc_collection_command_simple (mongoc_collection_t *collection,
                                  const bson_t *command,
                                  const mongoc_read_prefs_t *read_prefs,
                                  bson_t *reply,
                                  bson_error_t *error);

Parameters

• collection: A mongoc_collection_t.

• command: A bson_t containing the command to execute.

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

• reply: A location to initialize a bson_t. This should be on the stack.

• error: An optional location for a bson_error_t or NULL.

Description

This is a simplified version of mongoc_collection_command() that returns the first result document in reply. The collection’s read preference, read concern, and write concern are not applied to the command. The parameter reply is initialized even upon failure to simplify memory management.

This function tries to unwrap an embedded error in the command when possible. The unwrapped error will be propagated via the error parameter. Additionally, the result document is set in reply.

This function is not considered a retryable read operation.

Errors

Errors are propagated via the error parameter.

Returns

Returns true if successful. Returns false and sets error if there are invalid arguments or a server or network error.

This function does not check the server response for a write concern error or write concern timeout.

Example

The following is an example of executing the collection stats command.

#include <bson/bson.h>
#include <mongoc/mongoc.h>
#include <stdio.h>

static void
print_collection_stats (mongoc_collection_t *collection)
{
   bson_error_t error;
   const char *name;
   bson_t *cmd;
   bson_t reply;

   name = mongoc_collection_get_name (collection);
   cmd = BCON_NEW ("collStats", BCON_UTF8 (name));

   if (mongoc_collection_command_simple (
          collection, cmd, NULL, &reply, &error)) {
      str = bson_as_canonical_extended_json (&reply, NULL);
      printf ("%s\n", str);
      bson_free (str);
   } else {
      fprintf (stderr, "%s\n", error.message);
   }

   bson_destroy (&reply);
   bson_destroy (cmd);
}