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datalevin 2025-03-23
So I've been playing around with using datalevin to query arbitrary data sources.
(def db
[[0 :name "Bob"]
[0 :species "Parakeet"]
[0 :age 3]
[0 :owners 0 :age 2]
[0 :owners 0 :name "vigo"]
[0 :owners 0 :foods 0 :type "avocado"]
[0 :owners 1 :age 2]
[0 :owners 1 :name "Bob"]
[0 :owners 1 :foods 0 :type "apple"]
[0 :owners 1 :foods 1 :type "avocado"]
[1 :name "George"]
[1 :species "Goldfish"]
[1 :age 1]
[1 :owners 0 :age 2]
[1 :owners 0 :name "Bob"]])
(d/q
'[:find [?name ...]
:where
[?pet :owners _ :foods _ :type "avocado"]
[?pet :name ?name]]
db)
;; ["Bob"]
So my next question is there any reason why this doesn't work with pull? As far as I can tell it's because pull checks for a db (same in Datascript).
I'm going to explore changing that check to see if it would just work with pull
Huahai 2025-03-23T20:48:23.514679Z
Pull expects a triple representation, while queries work with relations, I.e. a collection of tuples. Triple is a special case of tuples
Huahai 2025-03-23T20:49:37.273869Z
Pull is really about scanning triple indices. What you are seeing with datalog working on data collections is about hash join on relations
Huahai 2025-03-23T20:58:58.888739Z
Bindings work not just with vectors, you can destruct map and nested data structures as well. See https://github.com/juji-io/datalevin/blob/a1bbfaa167755056b51dc39deb6405df7490f052/test/datalevin/test/query.clj#L248 for examples
👍 2
Ahmed Hassan 2025-03-23T21:03:55.355619Z
test-nested-bindings have single level nested map, is it ergonomic to query deeply nested map?
Huahai 2025-03-23T21:08:34.072279Z
Is it ergonomic? Depending on your personal taste? I guess. I don’t know.
Yeah, after I asked I realised even if pull did work. I probably wouldn't want it, as I'm mostly using this to transform external data into something that I can query in Datalog to extract the bits I care about and then convert to triples my database schema understands. This is all super useful!
Because if I can transform arbitrary edn data into a list of paths they can then be queried.
using datalog
Huahai 2025-03-23T20:14:08.444319Z
Yup