traversals about levelgraph HOT 7 OPEN

The problem is that as join is implemented now, i.e. as a "pipeline" of filters/amplifiers of possible solutions, it support no recursion, as the steps in the pipeline are fixed: they are the conditions in our join.
However, we can implement a new RecursiveJoinStream, a special step that does the same step upon itself, by calling join recursively.
The performance of this query will be very bad for large dataset, if they are not filtered by previous conditions.

Another alternative is to "fork" the pipeline: one for each hop level.

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A "black-box" approach is also feasible: you can do the first join, without the recursive part, and get the solutions. Then you can feed each solution to a new join statement: this is exactly what the RecursiveJoinStream will do.

Do you want to give it a go?

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About to get on flight back to Europe, might hack on this on plane.

Also, had a crazy idea:
what if you described a traversal by describing the possible transitions from a given starting node with a regular (style) expression?

I wrote this thing a while ago:
https://github.com/dominictarr/regular-stream

for stream-parsing regular patterns.

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Cool! I'm not so sure about the regexp thing, could you make an example?

Be careful on the query planner, after a traversal step it should avoid using a sort join stream. Look at the live branch for hints in how to deal with it.

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Ok, I got the regular expression: it seems a much better way for implementing a navigator api.

One point: there is no 'OR' as a join condition at the moment.

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Ok, I implemented breadth-first and deep-first here: https://github.com/mcollina/levelgraph-recursive

It is not merged in LevelGraph itself for experimenting purposes :).

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That looks interesting. Not sure if anyone has seen this but expert.js supports this feature too. https://github.com/ithailevi/expert

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