Minor - P4 Upserts require enforcing a uniqueness constraint via a query - in a sharded cluster the only way to do this is if the upsert query is targeted by the shard key. The error message "does not contain shard key", however, is a bit vague in that the shard key may be included in the update expression of the update, but the query also requires it.
Original description:
2.6 behavior:
mongos> sh.shardCollection("test.f1",{a:1})
{ "collectionsharded" : "test.f1", "ok" : 1 }
mongos> db.f1.update({x:1},{$setOnInsert:{a:1}},{upsert:true})
WriteResult({
"nMatched" : 0,
"nUpserted" : 0,
"nModified" : 0,
"writeError" : {
"code" : 61,
"errmsg" : "upsert { q: { x: 1.0 }, u: { $setOnInsert: { a: 1.0 } }, multi: false, upsert: true } does not contain shard key for pattern { a: 1.0 }"
}
})
2.4 behavior:
mongos> db.f1.update({x:1},{$setOnInsert:{a:1}},{upsert:true})
Cannot use commands write mode, degrading to compatibility mode
WriteResult({
"nMatched" : 0,
"nUpserted" : 0,
"writeError" : {
"code" : 13123,
"errmsg" : "Can't modify shard key's value. field: a: 1.0 collection: test.f1"
}
})