Man page - mongoc_collection_estimated_document_count(3)

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Manual

MONGOC_COLLECTION_ESTIMATED_DOCUMENT_COUNT

SYNOPSIS
PARAMETERS
DESCRIPTION
Behavior
ERRORS
RETURNS
EXAMPLE
AUTHOR
COPYRIGHT

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 maybe- NULL pointer to overwritable storage for a bson_t to contain the results.
	•		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

2009-present, MongoDB, Inc.