---
name: "mongoc_collection_count_documents"
section: "3"
platform: "linux"
package: "libmongoc-doc"
version: "1.30.4-1+deb13u3"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/mongoc_collection_count_documents"
---

# mongoc\_collection\_count\_documents(3)

## SYNOPSIS

```
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);
```

## PARAMETERS

- •

  **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 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. 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*.

## DESCRIPTION

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

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 *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);
   }
}
```

## MIGRATING FROM DEPRECATED COUNT FUNCTIONS

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:

| | |
| --- | --- |
| Operator | Replacement |
| $where | *$expr* |
| $near | *$geoWithin* with *$center* |
| $nearSphere | *$geoWithin* with *$centerSphere* |

$expr requires MongoDB 3.6+

**SEE ALSO:**

```
mongoc_collection_estimated_document_count()
```

## AUTHOR

MongoDB, Inc

## COPYRIGHT

2009-present, MongoDB, Inc.