Aggregation issue with Mongo 3.6

Question

I was using the aggregate function without any problem connecting a 3.4 mongodb.

When I change to a 3.6 db,

I've got the message: The 'cursor' option is required, except for aggregate with the explain argument.

Sorry if it's already posted. I am unable to find any solutions

Answer 1

In mongo 3.6 there has been changes while using aggregate you have to use cursor, unless you include the explain option, you must specify the cursor option. I faced same error as you were facing. Now you have to do it like

this.aggregate( [
        { $unwind : "$tags" },
        {$group: {_id: '$tags', count: { $sum: 1} }},
        {$sort: { count: 1 }}
            ] ).cursor({}).exec();

Now you can use cursor method cursor.toArray() to return an array that contains all the documents from a cursor. Cursors returned from aggregation only supports cursor methods that operate on evaluated cursors like cursor.toArray(), to know about more cursor methods you can click here and get further.