mongoc_collection_count_with_opts - Man Page

int64_t
mongoc_collection_count_with_opts (mongoc_collection_t *collection,
                                   mongoc_query_flags_t flags,
                                   const bson_t *query,
                                   int64_t skip,
                                   int64_t limit,
                                   const bson_t *opts,
                                   const mongoc_read_prefs_t *read_prefs,
                                   bson_error_t *error);

• collection: A mongoc_collection_t.
• flags: A mongoc_query_flags_t.
• query: A bson_t containing the query.
• skip: A int64_t, zero to ignore.
• limit: A int64_t, zero to ignore.
• opts: A bson_t, NULL to ignore.
• read_prefs: An optional mongoc_read_prefs_t, otherwise uses the collection's read preference.
• error: An optional location for a bson_error_t or NULL.

opts may be NULL or a BSON document with additional command options:

• readConcern: Construct a mongoc_read_concern_t and use mongoc_read_concern_append() to add the read concern to opts. See the example code for mongoc_client_read_command_with_opts(). Read concern requires MongoDB 3.2 or later, otherwise an error is returned.
• sessionId: First, construct a mongoc_client_session_t with mongoc_client_start_session(). You can begin a transaction with mongoc_client_session_start_transaction(), optionally with a mongoc_transaction_opt_t that overrides the options inherited from collection, and use mongoc_client_session_append() to add the session to opts. See the example code for mongoc_client_session_t.
• collation: Configure textual comparisons. See Setting Collation Order, and the MongoDB Manual entry on Collation. Collation requires MongoDB 3.2 or later, otherwise an error is returned.
• serverId: To target a specific server, include an int32 "serverId" field. Obtain the id by calling mongoc_client_select_server(), then mongoc_server_description_id() on its return value.

This function shall execute a count query on the underlying 'collection'. The bson 'query' is not validated, simply passed along as appropriate to the server.  As such, compatibility and errors should be validated in the appropriate server documentation.

The mongoc_read_concern_t specified on the mongoc_collection_t will be used, if any. If read_prefs is NULL, the collection's read preferences are used.

In addition to the standard functionality available from mongoc_collection_count, this function allows the user to add arbitrary extra keys to the count.  This pass through enables features such as hinting for counts.

For more information, see the query reference at the MongoDB website.

This function is considered a retryable read operation. Upon a transient error (a network error, errors due to replica set failover, etc.) the operation is safely retried once. If retryreads is false in the URI (see mongoc_uri_t) the retry behavior does not apply.

Errors are propagated via the error parameter.

-1 on failure, otherwise the number of documents counted.

Basic Counting

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

static void
print_query_count (mongoc_collection_t *collection, bson_t *query)
{
   bson_error_t error;
   int64_t count;
   bson_t opts;

   bson_init (&opts);
   BSON_APPEND_UTF8 (&opts, "hint", "_id_");

   count = mongoc_collection_count_with_opts (
      collection, MONGOC_QUERY_NONE, query, 0, 0, &opts, NULL, &error);

   bson_destroy (&opts);

   if (count < 0) {
      fprintf (stderr, "Count failed: %s\n", error.message);
   } else {
      printf ("%" PRId64 " documents counted.\n", count);
   }
}

Counting with Collation

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

static void
print_query_count (mongoc_collection_t *collection, bson_t *query)
{
   bson_t *selector;
   bson_t *opts;
   bson_error_t error;
   int64_t count;

   selector = BCON_NEW ("_id", "{", "$gt", BCON_UTF8 ("one"), "}");

   /* "One" normally sorts before "one"; make "one" come first */
   opts = BCON_NEW ("collation",
                    "{",
                    "locale",
                    BCON_UTF8 ("en_US"),
                    "caseFirst",
                    BCON_UTF8 ("lower"),
                    "}");

   count = mongoc_collection_count_with_opts (
      collection, MONGOC_QUERY_NONE, query, 0, 0, opts, NULL, &error);

   bson_destroy (selector);
   bson_destroy (opts);

   if (count < 0) {
      fprintf (stderr, "Count failed: %s\n", error.message);
   } else {
      printf ("%" PRId64 " documents counted.\n", count);
   }
}

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