Beginner datalog query in XTQL v2 w/ Clojure

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,
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Okay correction - I spoke too soon(!) - thanks to help from @jarohen I can present the “correlated not exists” workaround:

(->
  (unify
    (join (->
            (unify
              (rel [{:o-id "o2"} {:o-id "o3"}] [o-id])
              (from :ts [{:xt/id t-id} o-ids])
              (unnest {o-id o-ids}))
            (aggregate {:matched-t-ids (array-agg t-id)}))
      [matched-t-ids])
    (from :vs [{:xt/id vpid} {:t-ids vp-t-ids}])
    (where (not (exists? (->
                           (rel [{}] [])
                           (unnest {:matched-t-id $matched-t-ids})
                           (where (not (exists? (->
                                                  (rel [{}] [])
                                                  (unnest {:vp-t-id $vp-t-ids})
                                                  (where (= $matched-t-id vp-t-id)))
                                         {:args [matched-t-id {:vp-t-ids $vp-t-ids}]}))))
                  {:args [matched-t-ids vp-t-ids]}))))
  (return vpid))

Given the data:

[:put-docs :ts
 {:xt/id "t1" :o-ids ["o1" "o2"]}
 {:xt/id "t2" :o-ids ["o2" "o3"]}
 {:xt/id "t3" :o-ids ["o4" "o4"]}
 {:xt/id "t4" :o-ids ["o1" "o5"]}
 {:xt/id "t5" :o-ids ["o9" "o8"]}]

[:put-docs :vs
 {:xt/id "v1" :t-ids ["t1" "t4"]}
 {:xt/id "v2" :t-ids ["t1" "t2" "t3"]}
 {:xt/id "v3" :t-ids ["t1" "t3"]}
 {:xt/id "v4" :t-ids ["t1" "t4" "t2"]}]

Produces:

{:vpid "v2"}
{:vpid "v4"}

You can test it out on the highly experimental XT fiddle: https://fiddle.xtdb.com/

<@ or equivalent would undoubtedly be nicer, but hopefully that workaround at least demonstrates the compositional powers of XTQL.