Provided by: libmongoc-doc_1.24.3-1_all 
NAME
mongoc_collection_count_documents - mongoc_collection_count_documents()
SYNOPSIS
int64_t
mongoc_collection_count_documents (mongoc_collection_t *collection,
const bson_t *filter,
const bson_t *opts,
const mongoc_read_prefs_t *read_prefs,
bson_t *reply,
bson_error_t *error);
PARAMETERS
• collection: A mongoc_collection_t.
• filter: A bson_t containing the filter.
• opts: A bson_t, NULL to ignore.
• read_prefs: A mongoc_read_prefs_t or NULL.
• reply: A location for an uninitialized bson_t to store the command reply, NULL to
ignore. If not NULL, reply will be initialized.
• 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.
• skip: An int specifying how many documents matching the query should be skipped before
counting.
• limit: An int specifying the maximum number of documents to count.
• comment: A bson_value_t specifying the comment to attach to this command. The comment
will appear in log messages, profiler output, and currentOp output. Only string values
are supported prior to MongoDB 4.4.
• hint: A document or string that specifies the index to use to support the query
predicate.
Other options are included in the sent aggregate command. For a list of all options, see
the MongoDB Manual entry on the aggregate command.
DESCRIPTION
This functions executes a count query on collection. In contrast with
mongoc_collection_estimated_document_count(), the count returned is guaranteed to be
accurate.
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
Errors are propagated via the error parameter.
RETURNS
-1 on failure, otherwise the number of documents counted.
EXAMPLE
#include <bson/bson.h>
#include <mongoc/mongoc.h>
#include <stdio.h>
static void
print_count (mongoc_collection_t *collection, bson_t *filter)
{
bson_error_t error;
int64_t count;
bson_t* opts = BCON_NEW ("skip", BCON_INT64(5));
count = mongoc_collection_count_documents (
collection, filter, opts, NULL, NULL, &error);
bson_destroy (opts);
if (count < 0) {
fprintf (stderr, "Count failed: %s\n", error.message);
} else {
printf ("%" PRId64 " documents counted.\n", count);
}
}
MIGRATING FROM DEPRECATED COUNT FUNCTIONS
When migrating to mongoc_collection_count_documents() from the deprecated
mongoc_collection_count() or mongoc_collection_count_with_opts(), the following query
operators in the filter must be replaced:
┌────────────┬───────────────────────────────┐
│Operator │ Replacement │
├────────────┼───────────────────────────────┤
│$where │ $expr │
├────────────┼───────────────────────────────┤
│$near │ $geoWithin with $center │
├────────────┼───────────────────────────────┤
│$nearSphere │ $geoWithin with $centerSphere │
└────────────┴───────────────────────────────┘
$expr requires MongoDB 3.6+
SEE ALSO:
mongoc_collection_estimated_document_count()
AUTHOR
MongoDB, Inc
COPYRIGHT
2017-present, MongoDB, Inc