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.
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.
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()
COPYRIGHT¶
2017-present, MongoDB, Inc
