tonsky / tonsky/datascript

Multiple occurrences of query vars in pattern and aggregates

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#428 2 comments 0 reactions 0 assignees View on GitHub

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Dominant language
Clojure
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Description

With this query:

(q '[:find (count ?e) .
     :with ?i
     :where [?e :r ?e ?i]]
   [[1 :r 1 10]
    [2 :r 1 11]])

I get 1 with Datomic but 2 in datascript. It appears the test for two occurrences of a query variable is tested too late.

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  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.

Research direction

Start by reproducing the query in the issue and comparing its result with Datomic's expected result. Trace how repeated query variables are handled in query evaluation, especially with aggregates, then add a regression test for the supplied data and query. Done means the query returns 1, matching Datomic.

Written by the indexing model from the issue text.

Assessment

Tech stack
clojure
Domain
databases
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
35/100

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