Hacker News Reader

Hacker News

Comment by DeepDuh | Hacker News Reader

Parent Full thread

DeepDuh

That's also my conclusion. However I'm not aware of a DBMS that

- is document based

- can easily replicate to laptops and embedded devices

- has all the security I want, e.g. encryption, per document security

- has the bindings I want and/or a new binding can easily be implemented ad-hoc

Given the advantages and disadvantages I'm leaning towards CouchDB and rolling my own security wrapper. IMO that's still better than going with an RDBMS and then implementing replication[1]. How do you see this?

[1]edit: and also giving up the document based approach, thus not having arbitrary mapping from the get go.

View on HN

I love couchdb for its replication, not only did I use it for a previous company I worked for and still contract with, I'm using it for my 'big idea' project. Once you have data replication you do need some kind of different approach to user/document security - after all they can take the data they have and do anything with it - so you need to treat replication as data input and validate there, like couchDB does.

I think the real downsides are scaling and performance but there are options at least. Given that TouchDB is essentially couchdb mapped onto sqlite I do wonder if there are going to be good options to map couchdb replication onto postgres in future.

oh, so TouchDB maps to sqlite? Does that work generally? Let's say my documents have lists of maps of tuples of lists - will it create the appropriate table structure in sqlite?

The use cases I have in mind don't need the DB to scale to more than a few ten thousand users. Should be ok with a two or three replicated nodes I think, from my experience with Lotus Notes.

I think each document is a row and it parses it to native structures on load. I think I saw something on the dev list about that being improved - but its something to check if it matters.

[edit: sorry, I replied here, because it wouldn't let me reply to your other answer first and I thought it was because we've reached some kind of maximum depth]

Thanks, I see. Ok, if it's just string or binary based it will work from a correctness standpoint. I'd expect big performance problems with ad-hoc views (if they even exist here), but these shouldn't be used in production anyways. Also, I'd expect replication to take quite a bit longer because it needs to map every document with changes, so there's going to be a tradeoff between initialization time and replication time between the two approaches.

I'm thinking it's going to be beneficial for larger databases to have a TouchDB 'server' somewhere, which constantly replicates with CouchDB and sends the devices a complete snapshot sqlite file for the initial setup. After that, they can talk to CouchDB directly. Otherwise it could take like half an hour to initialize a 50MB DB on a device, which is not really feasible.

In fact for a while you could only have adhoc views, but my knowledge is 6 months out of date.

Yes definitely do that. I bundle the sqlite in the app store updates and then mount that as an external db and pull from itself - its a bit awkward but it worked. I had to write the external db stuff, but it was pretty easy.

Reply on news.ycombinator.com