Update embedded object inside array inside array in MongoDB - mongodb

Question

I have document like
{
id : 100,
heros:[
{
nickname : "test",
spells : [
{spell_id : 61, level : 1},
{spell_id : 1, level : 2}
]
}
]
}
I can't $set spell's level : 3 with spell_id : 1 inside spells that inside heros with nickname "test. I tried this query:
db.test.update({"heros.nickname":"test", "heros.spells.spell_id":1},
{$set:{"heros.spells.$.level":3}});
Errror i see is
can't append to array using string field name [spells]
Thanks for help.

Answer 1

You can only use the $ positional operator for single-level arrays. In your case, you have a nested array (heros is an array, and within that each hero has a spells array).
If you know the indexes of the arrays, you can use explicit indexes when doing an update, like:
> db.test.update({"heros.nickname":"test", "heros.spells.spell_id":1}, {$set:{"heros.0.spells.1.level":3}});

Answer 2

Try something like this:
db.test.find({"heros.nickname":"test"}).forEach(function(x) {
bool match = false;
for (i=0 ; i< x.heros[0].spells.length ; i++) {
if (x.heros[0].spells[i].spell_id == 1)
{
x.heros[0].spells[i].level = 3;
match = true;
}
}
if (match === true) db.test.update( { id: x.id }, x );
});
Apparently someone opened a ticket to add the ability to put a function inside the update clause, but it hasn't been addressed yet: https://jira.mongodb.org/browse/SERVER-458