Distributed Queries

A few weeks ago I was having a chat with the people from Fedora about the things they'd like/need in Mulgara. One of the features that came up was distributed queries. I recall that it was pretty simple when I did this (the naïve way) a few years ago. So I thought I'd have another go at it.

I've had a lot of things to get done lately, but as of this afternoon I have it running again (yay). Unfortunately I haven't had time to set up tests which start 2 servers and query them together, but my manual tests are all working fine. I'm able to describe models from multiple servers in the FROM clause of my queries, and also in the IN clauses.

My first priority is to get the tests written. Then in the longer term I need to get an intelligent algorithm going to properly distribute the query around the network. I know what needs doing, but it requires some help in the query optimizer, and can't be done entirely in the resolver. So I'll be waiting until I'm given some significant time for this feature before I get stuck into it.

In the meantime, I don't actually have any use cases which need optimized network activity for distributed query resolution, so I'm pretty happy that I have the feature going.