Group by field doesn't work in MongoDB - php

Question

I'm trying to calculate a sum of all records in my db, and I need to avoid duplicates. I wrote this code to group the records, but it doesn't work for me.
$pipeline = [
['$match' =>
$criteria->getCondition()],
['$group' =>
['_id' => '$order_id', 'total' => ['$sum' => '$'.$column]]]
];
$this->getDbConnection()->aggregate('ticket_cache', $pipeline);
Test request:
db.getCollection('ticket_cache').aggregate(
{
"$match":
{"event_id":64}
},
{
"$group" :
{"_id":"$order_id", "total": {"$sum":"$payment_amount"}}
})
Result:
/* 1 */
{
"result" : [
{
"_id" : NumberLong(7002),
"total" : 9000.0000000000000000
}
],
"ok" : 1.0000000000000000
}
Data in the db:
/* 1 */
{
"result" : [
{
"_id" : ObjectId("553f8b4fbfabe2772f8b4f51"),
"event_id" : NumberLong(64),
"ticket_id" : NumberLong(8563),
"ticket_code" : NumberLong(22062299),
"ticket_type_id" : NumberLong(391),
"ticket_created" : NumberLong(1430227620),
"ticket_deleted" : NumberLong(0),
"ticket_user_id" : NumberLong(2),
"ticket_used" : NumberLong(0),
"order_id" : NumberLong(7002),
"order_code" : NumberLong(517005),
"order_created" : NumberLong(1430227620),
"order_deleted" : NumberLong(0),
"order_sales_pipeline" : NumberLong(18),
"order_invoice_id" : NumberLong(4202),
"order_invoice_amount" : 3000.0000000000000000,
"order_invoice_created" : NumberLong(1430227641),
"order_invoice_deleted" : NumberLong(0),
"order_invoice_code" : NumberLong(420155),
"payment_id" : NumberLong(4365),
"payment_amount" : 3000.0000000000000000,
"payment_currency" : NumberLong(4),
"payment_author_id" : NumberLong(1),
"payment_type_id" : NumberLong(27),
"payment_created" : NumberLong(1430227641),
"payment_deleted" : NumberLong(0),
"create_time" : ISODate("2015-04-28T13:29:51.328Z")
},
{
"_id" : ObjectId("553f8b4fbfabe2772f8b4f4f"),
"event_id" : NumberLong(64),
"ticket_id" : NumberLong(8561),
"ticket_code" : NumberLong(49287433),
"ticket_type_id" : NumberLong(391),
"ticket_created" : NumberLong(1430227620),
"ticket_deleted" : NumberLong(0),
"ticket_user_id" : NumberLong(2),
"ticket_used" : NumberLong(0),
"order_id" : NumberLong(7002),
"order_code" : NumberLong(517005),
"order_created" : NumberLong(1430227620),
"order_deleted" : NumberLong(0),
"order_sales_pipeline" : NumberLong(18),
"order_invoice_id" : NumberLong(4202),
"order_invoice_amount" : 3000.0000000000000000,
"order_invoice_created" : NumberLong(1430227641),
"order_invoice_deleted" : NumberLong(0),
"order_invoice_code" : NumberLong(420155),
"payment_id" : NumberLong(4365),
"payment_amount" : 3000.0000000000000000,
"payment_currency" : NumberLong(4),
"payment_author_id" : NumberLong(1),
"payment_type_id" : NumberLong(27),
"payment_created" : NumberLong(1430227641),
"payment_deleted" : NumberLong(0),
"create_time" : ISODate("2015-04-28T13:29:51.316Z")
},
{
"_id" : ObjectId("553f8b4fbfabe2772f8b4f50"),
"event_id" : NumberLong(64),
"ticket_id" : NumberLong(8562),
"ticket_code" : NumberLong(24016753),
"ticket_type_id" : NumberLong(391),
"ticket_created" : NumberLong(1430227620),
"ticket_deleted" : NumberLong(0),
"ticket_user_id" : NumberLong(2),
"ticket_used" : NumberLong(0),
"order_id" : NumberLong(7002),
"order_code" : NumberLong(517005),
"order_created" : NumberLong(1430227620),
"order_deleted" : NumberLong(0),
"order_sales_pipeline" : NumberLong(18),
"order_invoice_id" : NumberLong(4202),
"order_invoice_amount" : 3000.0000000000000000,
"order_invoice_created" : NumberLong(1430227641),
"order_invoice_deleted" : NumberLong(0),
"order_invoice_code" : NumberLong(420155),
"payment_id" : NumberLong(4365),
"payment_amount" : 3000.0000000000000000,
"payment_currency" : NumberLong(4),
"payment_author_id" : NumberLong(1),
"payment_type_id" : NumberLong(27),
"payment_created" : NumberLong(1430227641),
"payment_deleted" : NumberLong(0),
"create_time" : ISODate("2015-04-28T13:29:51.326Z")
}
],
"ok" : 1.0000000000000000
}
Where did I go wrong?

Answer 1

Can you try with the below query. It assumes that the payment amount will always be same. Have a look at addToSet http://docs.mongodb.org/manual/reference/operator/update/addToSet/.
db.getCollection('ticket_cache').aggregate(
{ "$match": {"event_id":64} },
{ "$group" :
{"_id":"$order_id", "total": {"$addToSet":"$payment_amount"}}
},
{"$unwind": "$total"},
{"$group": {"_id": "null", "totalOdr": {"$sum": "$total"}}}
)