rules aren't correctly unifying

Open
#336 5 comments 0 reactions 0 assignees View on GitHub

Nobody has claimed this yet.

Assessment

Difficulty
5/5
Estimated time
Over a week
Newbie friendliness
25/100
Issue type
Bug
Clarity
Needs clarification
Activity status
Stale
Tech stack
clojure
Domain
databases

Research direction

The issue names no source files or tests. Reproduce both recursive-rule examples through db/q, then trace rule evaluation and unification from that entry point; done means the first query returns the expected root and the second no longer returns the unrelated entity or throws.

Written by the indexing model from the issue text.

Description

The problem: walk references until finding the root reference.

This example returns {:id :a :root 1} in the results as expected for datomic, but fails in datascript:

(let [c (db/empty-db {:id {:db/unique :db.unique/identity}})]
    (db/q '[:find (pull ?root [*]) :in $ ?id % :where [?e :id ?id] (root ?id ?root)]
          (db/db-with c [{:id :a :root 1} {:id :b :parent [:id :a]} {:id :c :parent [:id :b]} {:id :d :root 2}])
          :b
          '[[(root ?e ?e) (not [?e :parent _])]
            [(root ?e ?r) [?e :parent ?p] (root ?p ?r)]]))
;; => ExceptionInfo Insufficient bindings: none of #{?root} is bound in (not [?root :parent _])  clojure.core/ex-info (core.clj:4739)

This example throws an ArrayIndexOutOfBoundsException in datomic 🤷‍♂️ while in datascript returns too many results (however did it reach {:id :d}?):

(let [c (db/empty-db {:id {:db/unique :db.unique/identity}})]
    (db/q '[:find (pull ?root [*]) :in $ ?id % :where [?e :id ?id] (root ?id ?root)]
          (db/db-with c [{:id :a :root 1} {:id :b :parent [:id :a]} {:id :c :parent [:id :b]} {:id :d :root 2}])
          :b
          '[[(root ?e ?e) [?e :root _]]
            [(root ?e ?r) [?e :parent ?p] (root ?p ?r)]]))
;; => ([{:db/id 4, :id :d, :root 2}] [{:db/id 1, :id :a, :root 1}])
Dominant language
Clojure
Stars
5.8k
Forks
318
No merged PRs in 30d

Contributor guide

No contributing guide indexed for this repository

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

More from tonsky/datascript

All issues in tonsky/datascript

Similar issues

More Clojure issues

Get new issues in your inbox

A short digest of beginner-friendly GitHub issues.