About aggregate queries question

[dadaxixiyou]

mongoapi:runCmd([
{"aggregate", ?ORDER_TABLE},
{"cursor", #{ } },
{"pipeline",
{array,[
[
{"$match", #{status=>0}}
],
[
{"$group",[
{"_id","null"},
{"total", [{"$sum", "$amount"}]}
]}
]
]}
}
], ?MONGO_MASTER),

the query result is:
[{<<"cursor">>,
[{<<"firstBatch">>,
{array,[[{<<"_id">>,<<"null">>},{<<"total">>,1900}]]}},
{<<"id">>,0},
{<<"ns">>,<<"paycenter_db.pay_order">>}]},
{<<"ok">>,1.0}]

Can you give me a correct demonstration?
Cursor is a mandatory parameter, but I am not sure how to use it. Do I need to close cursor?

[SergejJurecko]

Cursor empty like in your example has no effect.

[dadaxixiyou]

I'm still not sure how to use the cursor properly,can you give me example?