Graphs in RavenDB: Inconsistency Abhorrence

In my previous post, I discussed some options for changing the syntax of graph queries in RavenDB from Cypher to be more in line with the rest of the RavenDB Query Language. We have now completed that part and can see the real impact it has on the overall design.

In one of the design review, one of the devs (who have built non-trivial applications using Neo4J) complained that the syntax is now much longer. Here are the before and after queries to compare:

The key, from my perspective, is that the new form is more explicit and easier to read after the fact. Queries tend to grow more complex over time, and they are being read a lot more often than written). As such, I absolutely want to lean toward being readable over being terse.

The example above just show the extra characters that you need to write. Let’s talk about something that is a bit more complex:

Now we have a lot more text, but it is a lot easier to understand what is going on. Focus especially on the Lines edge, where we can very clearly separate what constitute the selection on the edge, the filter on the edge and what is the property that contains the actual linked document ID.

The end result is that we now have a syntax that is a lot more consistent and approachable. There are other benefits, but I’ll show them off in the next post.

A major source of annoyance for me with this syntax was how to allow anonymous aliases. In the Cypher syntax we used, you could do something like:

There is a problem with how to express this kind of syntax of anonymous aliases with the Collection as alias mode. I initially tried to make it work by saying that we’ll look at the rest of the query and figure it out. But that just felt wrong. I didn’t like this inconsistency. I want a parse tree that I can look at in isolation and know what is going on. Simplifying the language is something that pays dividends over time, so I eventually decided that the query above will look this with the next syntax:

There is a lot of precedence of using underscore as the “I don’t care” marker, so that works nice and resolves any ambiguities in the syntax.