Upsert a document with shard key

[João Paulo Farias]

Hi!

I am trying to use mgo with a sharded mongo cluster. The struct I am using has the shard key in it, so when I try to do something like:

type MyStruct struct {
  ListingKey string
  // other fields...
}
var x MyStruct{
  "123",
  // other fields
}
info, err := session.DB("mydb").C("mycollection").Upsert(bson.M{"listingkey": "123"}, x)

This gives me an error:

Can't modify shard key's value. field: listingkey: "123" collection: mydb.mycollection

How do I go around this?

Thanks,

-- JP

[Gustavo Niemeyer]

Hi João,

This question and other related ones are answered in the following FAQ:

http://docs.mongodb.org/manual/faq/sharding/

Please let us know if there's anything else we can help with.

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--

gustavo @ http://niemeyer.net

[João Paulo Farias]

I know how the update works, my question is how can I tell mgo to not include that field in the update part...

Because I am using a struct and not building a bson.M{} everytime I want to do an upsert it always includes all fields in the struct from what I can tell.

Is the solution to this to manually build the bson.M{} without that field?

Thanks,

--

JP

[Gustavo Niemeyer]

So you just want to avoid marshaling the struct field?

You can do that using a field tag:

type T struct {
Field string `bson:"-"`
}



On Wed, Feb 25, 2015 at 5:44 PM, João Paulo Farias

[João Paulo Farias]

Well I still want it to get the field from mongo when it loads, it just doesn't need to send it on the updates. This would completely ignore the field both ways...

[Gustavo Niemeyer]

You may also use the omitempty tag, so it will be omitted only if not provided:

Field string `bson:",omitempty"`

On Wed, Feb 25, 2015 at 5:58 PM, João Paulo Farias

[João Paulo Farias]

Perfect! That worked as expected.

Thanks Gustavo,

--

JP