Recursive entities

[dmeehan1968]

I'm looking for a solution to creating recursive entities, such as a group that has sub groups.

This can be modelled with attributes for groupId and parentGroupId, with a primary index that just uses groupId as a PK, to allow for direct retrieval of the group regardless of whether it has a parent.

It feels like I then need a secondary index with a collection, so that I can retrieve either the group alone, or the group and subgroups. If I was doing this in Dynamo directly, I'd be able to conditionally define the secondary index, but in Electro it seems that although I can either define or not define the secondary, I can't control which composite keys go into it, so it can't be populated with the group itself at the 'root' of the partition. template doesn't help as its only pattern matching, i.e. not able to expression conditional logic.

[tywalch]

Can you demonstrate more concretely what you're trying to accomplish? If you're able to accomplish this without Electro what does that look like?

[dmeehan1968]

Thanks for the speedy response, and on reflection I realise that I was getting confused by the 'collection' functionality of EDB.

Here is what I have been doing, and can model the same in EDB with a condition on the GSI to omit the index if the parentGroup is ''.

Primary PK groupId
GSI PK parentGroupId
GSK SK groupId

I thought somehow that collections let me put the group also in the GSI.