SYNOPSIS

          mongoc_change_stream_t*
          mongoc_database_watch (const mongoc_database_t *db,
                                 const bson_t *pipeline,
                                 const bson_t *opts) BSON_GNUC_WARN_UNUSED_RESULT;

       A  helper  function  to create a change stream. It is preferred to call this function over
       using a raw aggregation to create a change stream.

       This function uses the read preference and read concern of the  database.  If  the  change
       stream  needs  to re-establish connection, the same read preference will be used. This may
       happen if the change stream encounters a resumable error.

       WARNING:
          A change stream is only supported with majority read concern.

       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.

PARAMETERS

       • db: A mongoc_database_t specifying the database which the change stream listens to.

       • pipeline: A bson_t representing an aggregation pipeline appended to the  change  stream.
         This may be an empty document.

       • opts: A bson_t containing change stream options.

       opts may be NULL or a BSON document with additional command options:

       • batchSize:  An  int32  representing number of documents requested to be returned on each
         call to mongoc_change_stream_next()

       • resumeAfter: A Document representing the logical starting point of  the  change  stream.
         The  result  of  mongoc_change_stream_get_resume_token() or the _id field  of any change
         received from a change stream can be used here. This option is mutually  exclusive  with
         startAfter and startAtOperationTime.

       • startAfter:  A  Document  representing  the logical starting point of the change stream.
         Unlike resumeAfter, this can resume  notifications  after  an  "invalidate"  event.  The
         result  of  mongoc_change_stream_get_resume_token()  or  the  _id  field   of any change
         received from a change stream can be used here.  This option is mutually exclusive  with
         resumeAfter and startAtOperationTime.

       • startAtOperationTime: A Timestamp. The change stream only provides changes that occurred
         at or after the specified timestamp. Any command run against the server will  return  an
         operation time that can be used here. This option is mutually exclusive with resumeAfter
         and startAfter.

       • maxAwaitTimeMS:  An  int64  representing  the  maximum  amount  of  time   a   call   to
         mongoc_change_stream_next() will block waiting for data

       • fullDocument:  An  optional  UTF-8 string. Set this option to "default", "updateLookup",
         "whenAvailable", or "required", If unset, The string  "default"  is  assumed.  Set  this
         option  to  "updateLookup" to direct the change stream cursor to lookup the most current
         majority-committed version of the document associated to an update change stream event.

       • fullDocumentBeforeChange: An optional UTF-8 string. Set this option to  "whenAvailable",
         "required", or "off". When unset, the default value is "off". Similar to "fullDocument",
         but returns the value of the document before the associated change.

       • showExpandedEvents: Set to true to return an expanded  list  of  change  stream  events.
         Available only on MongoDB versions >=6.0

       • 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.

RETURNS

       A     newly    allocated    mongoc_change_stream_t    which    must    be    freed    with
       mongoc_change_stream_destroy() when no longer in use. The returned  mongoc_change_stream_t
       is    never    NULL.    If    there    is   an   error,   it   can   be   retrieved   with
       mongoc_change_stream_error_document(), and subsequent calls to mongoc_change_stream_next()
       will return false.

       SEE ALSO:
          mongoc_client_watch()

          mongoc_collection_watch()

AUTHOR

       MongoDB, Inc

COPYRIGHT

       2017-present, MongoDB, Inc