add new item value into an embedded document in mongoDB - mongodb

Question

I have a document :
{
"_id" : ObjectId("550c00f81bcc15211016699b"),
"name" : "book3",
"author" : "mno",
"publisher" : "pub",
"testa" : [
{
"item1" : "item1",
"item2" : "item2"
}
]
}
All I want to do is add another item in testa like:
{
"_id" : ObjectId("550c00f81bcc15211016699b"),
"name" : "book3",
"author" : "mno",
"publisher" : "pub",
"testa" : [
{
"item1" : "item1",
"item2" : "item2",
"item3 : "item3"
}
]
}
I tried using
db.books.update(
{ "author":"mno" },
{ $addToSet: { testa : {"item3":"item3"} } }
)
this gives
{
"_id" : ObjectId("550c05261bcc15211016699c"),
"name" : "book3",
"author" : "mno",
"publisher" : "pub",
"testa" : [
{
"item1" : "item1",
"item2" : "item2"
},
{
"item3" : "item3"
}
]
}
and i tried
db.books.update(
{ "author":"mno" , "testa.item1" : "item1"},
{ $set : {"testa.0" : {"item3":"item3"}}},
{upsert : true / false}
)
this gave
{
"_id" : ObjectId("550c05fa1bcc15211016699d"),
"name" : "book3",
"author" : "mno",
"publisher" : "pub",
"testa" : [
{
"item3" : "item3"
}
]
}
Am I doing something wrong, I checked everywhere
Insert an embedded document to a new field in mongodb document
and
Update or replace an embedded document in MongoDB collection
I tried wierd things... but.... Please help me get the query right
I also tried these using the C# driver
like
WriteConcernResult res = booksColl.Update(query, Update.Set("testa.$.item1", "itemedited"),UpdateFlags.Upsert);

Answer 1

The following statement should work
db.books.update(
{ "author":"mno" },
{ $set: { "testa.0.item3" : "item3"} }
)
You can use the dot notation to specify items in the array and then you can just set the new item3 field to what ever value you wish. You nearly had it right in your examples above - you just need to specify "testa.0.item3" instead of "testa.0"
I would agree with #chridam's comment above though and changing the schema would make the document easier to work with going forward. It might be some extra work now but it will save you in the long run.

Answer 2

Actually you don't have a collection of items, you have a collections of documents which have items as keys:values, if this is the goal, the update may be:
> db.books.update({ "author":"mno" },{$set: {"testa.0.item3":"item3"}})
WriteResult({ "nMatched" : 1, "nUpserted" : 0, "nModified" : 1 })
> db.books.find().pretty()
{
"_id" : ObjectId("550c00f81bcc15211016699b"),
"name" : "book3",
"author" : "mno",
"publisher" : "pub",
"testa" : [
{
"item1" : "item1",
"item2" : "item2",
"item3" : "item3"
}
]
}