datascript 2018-11-01 | Slack Archive

mrchance18:11:56

I have a somewhat unusual question: Given an AST for a programming language in a Datascript db, is it possible to identify dependencies with their db id, if all dependencies are db.type/ref? One problem I see is that they might not be immediate children of the node, but further down the tree. I know that datalog supports recursive queries, but my datalog-fu isn't strong enough for that (yet) 😉 The nodes are quite inhomogeneous (It's not a lisp tree sadly), so enumerating all possibilities by hand would be somewhat tedious, but theoretically possible

fmjrey18:11:13

Maybe some inspiration? https://stackoverflow.com/questions/42457136/recursive-datalog-queries-for-datomic-really-slow

fmjrey18:11:57

Actually this is a better example: https://github.com/tonsky/datascript/blob/1661c524b544fa0c212bc2db65ef7ad22cecb319/test/datascript/test/pull_api.cljc#L212

mrchance18:11:23

Cool, thanks, will check

mrchance18:11:51

Ah, actually the frontpage itself has a good example too:

(d/q '[ :find  ?u1 ?u2
        :in    $ %
        :where (follows ?u1 ?u2) ]
      [ [1 :follows 2]
        [2 :follows 3]
        [3 :follows 4] ]
     '[ [(follows ?e1 ?e2)
         [?e1 :follows ?e2]]
        [(follows ?e1 ?e2)
         [?e1 :follows ?t]
         (follows ?t ?e2)] ])

I was looking for something like that, coding it to a custom rule

mrchance18:11:40

I would expect that the pull based queries to have some issues dealing with cases where there can be more intermediate immediate steps with different child attributes

mrchance20:11:01

I found that I can generate this rule from the schema, that's pretty awesome 😈

2018-11-01

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