Provided by: libmongoc-doc_1.22.1-1_all 
NAME
mongoc_collection_estimated_document_count - mongoc_collection_estimated_document_count()
SYNOPSIS
int64_t
mongoc_collection_estimated_document_count (mongoc_collection_t *collection,
const bson_t *opts,
const mongoc_read_prefs_t *read_prefs,
bson_t *reply,
bson_error_t *error);
PARAMETERS
• collection: A mongoc_collection_t.
• 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. Requires MongoDB 4.4
or later.
For a list of all options, see the MongoDB Manual entry on the count command.
DESCRIPTION
This functions executes a count query on collection. In contrast with
mongoc_collection_count_documents(), the count returned is not 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.
Behavior
This method is implemented using the count command. Due to an oversight in versions
5.0.0-5.0.8 of MongoDB, the count command was not included in version "1" of the Stable
API. Applications using this method with the Stable API are recommended to upgrade their
server version to 5.0.9+ or disable strict mode (via :symbol:`mongoc_server_api_strict())
to avoid encountering errors.
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 *query)
{
bson_error_t error;
int64_t count;
bson_t* opts = BCON_NEW ("skip", BCON_INT64(5));
count = mongoc_collection_estimated_document_count (
collection, 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);
}
}
SEE ALSO:
mongoc_collection_count_documents()
Count: Behavior in the MongoDB Manual
AUTHOR
MongoDB, Inc
COPYRIGHT
2017-present, MongoDB, Inc
1.22.1 Aug 02, 2MONGOC_COLLECTION_ESTIMATED_DOCUMENT_COUNT(3)