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.
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 *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()
Author
MongoDB, Inc
Copyright
2017-present, MongoDB, Inc
Info
Jan 06, 2022 1.20.1 libmongoc