Could someone shed some more light on the NoSuchKey node?

Questions
1

I found the documentation on it rather sparse.

2 Likes
2

First things first, the docs and the implementation are a bit misaligned: #7113

When you execute a lookupByKey in DAML, a NodeLookupByKey is inserted in the transaction graph:

message NodeLookupByKey {
    com.daml.lf.value.Identifier template_id = 1;
    KeyWithMaintainers key_with_maintainers = 2;
    reserved 3; // was contract_id
    com.daml.lf.value.ContractId contract_id_struct = 4;
}

message KeyWithMaintainers {
    com.daml.lf.value.VersionedValue key = 1;
    repeated string maintainers = 2; // the maintainers induced by the key
}

key_with_maintainers.key and template_id correspond to the key you looked up. key_with_maintainers.maintainers are the maintainers of the key. contract_id_struct is the contract id if it exists. The NoSuchKey node of the docs is corresponds exactly to a NodeLookupByKey with an empty contract_id_struct

During validation the validators of that node which in an idealized system are exactly the maintainers, check that key_with_maintainers.key resolves (or doesn’t resolve) to contract_id_struct for template template_id. That’s all there’s to it. Did that answer your question?

2 Likes
3

This explains the NodeLookupByKey, but in the original thread a node called NoSuchKey is mentioned. Looking at the linked issue this node does not actually exist. So that answers my question. Thanks!

1 Like