It appears to me that the FtsEngineDriver.Search.OutputType is missing one parameter.
The declaration of the FtsEngineDriver.Search.OutputType in the search packages defines two parameters: ids and stopwords.
select acs_sc_msg_type__new (
'FtsEngineDriver.Search.OutputType',
'ids:integer[],stopwords:string[]'
);
However, the search implementation in openfts-driver returns an extra parameter: count. Shouldn't the count parameter have been included in the FtsEngineDriver.Search.OutputType definition?