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Infinite loop in rule solver

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#277 1 comment 0 reactions 0 assignees View on GitHub

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Assessment

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

Research direction

Start by running the provided ds.db_with, ds.q, and rules reproduction, then compare it with the transitive-closure example in the README. Trace the rule solver reached by ds.q and verify that this recursive rule query terminates and returns the expected friends results.

Written by the indexing model from the issue text.

Description

The following code will result in the query hanging

var ds = require("datascript")

var db = ds.db_with(ds.empty_db(), [
    {
        "left": "aaron",
        "right": "barbara"
    },
    {
        "left": "aaron",
        "right": "chris"
    }
])

var rules = `[
    [
        (friends ?a ?b)
        [?i "left" ?a]
        [?i "right" ?b]
    ]
    [
        (friends ?a ?b)
        (friends ?a ?c)
        (friends ?c ?b)
    ]
]`

console.log(ds.q(`[:find ?a ?b :in $ % :where (friends ?a ?b)]`, db, rules))

It's fairly similar to the transitive closure example in the README, but it uses an additional call to the rule in the non-base case. My understanding is that datalog queries should always terminate, so apologies if this isn't actually a bug.

Dominant language
Clojure
Stars
5.8k
Forks
318
PR merge metrics
No merged PRs in 30d

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