Group By key Meteor Collection - mongodb

Question

Hello I've searched a lot before asking the question and still have not found any decent answer to my question.
I have a collection (it's copying from MSSQL table every x second) like this: https://ekhmoi.tinytake.com/sf/MzU2MTcwXzIwNDcxNTg
As you can see there are fields which has the same key (MessageId).
My goal is some kind of grouping them, by taking MessageId + Message(of each record which has the same MessageId) and finally i will insert it to new Collection.
so final result should look like this:
https://ekhmoi.tinytake.com/sf/MzU2MTc3XzIwNDcyMDY
Any idea how can i do this ?

Answer 1

You can use aggregation for grouping your collection data to get your final result and the process is actually very simple.
First of all run meteor add meteorhacks:aggregate and meteor add mikowals:batch-insert if you have not yet added these two packages.
Assuming CollectionA is the first collection and CollectionB is the second collection. Here is how I would group data from Collection A and write the final result in CollectionB:
let pipeline = [
{$project: {TraceId: 1, MessageId: 1, Message: 1}},
{$group: {
_id: "$MessageId",
Message: {$push: "$Message"},
TraceId: {$first: "$TraceId"}
}},
{$project: {
_id: 0,
MessageId: "$_id",
Message: 1,
TraceId: 1
}}
];
let groupedData = CollectionA.aggregate(pipeline);
CollectionB.batchInsert(groupedData);
Note that this example is just the representation of my idea so it may be not working if you copy paste directly to your code.