mongoc_collection_count_documents − mongoc_collection_count_documents()
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);
• |
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.
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 are propagated via the error parameter.
−1 on failure, otherwise the number of documents counted.
#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); } }
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:
$expr requires MongoDB 3.6+
SEE ALSO:
mongoc_collection_estimated_document_count()
MongoDB, Inc
2017-present, MongoDB, Inc