Comments (4)
garrett-hopper
commented on June 9, 2024
This will need to be implemented in Datalevin directly (rather than in Datascript and duplicated here), as Datascript does not support :db/tupleValue (or :db/tupleValues) at all.
From @huahaiy regarding Datascript not supporting homogenous or heterogeneous tuples
Datascript only supports composite Tuples, because it does not differentiate data types, they are all clojure data, no strings, int, etc
Relevant Slack thread for anyone in the future: https://clojurians.slack.com/archives/C01RD3AF336/p1691260941968389
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garrett-hopper
commented on June 9, 2024
This appears to have been my own misunderstanding of Datomic's query syntax when it comes to tuples.
(There is still an issue with negative number tempids not being recognized in tuple types.)
It appears to work as expected when I use untuple correctly
(let [schema {:parent/children {:db/valueType :db.type/tuple
:db/tupleTypes [:db.type/ref :db.type/long]
:db/cardinality :db.cardinality/many}
:parent/name {:db/valueType :db.type/string
:db/unique :db.unique/identity}
:child/name {:db/valueType :db.type/string
:db/unique :db.unique/identity}}
conn (d/create-conn nil schema)
tempids (:tempids
(d/transact! conn [{:db/id -1
:child/name "Child 1"}
{:db/id -2
:child/name "Child 2"}
{:db/id -3
:parent/name "Parent 1"}
{:db/id -4
:parent/name "Parent 2"}]))]
;; Work around tempids not working in tuple types
(d/transact! conn [{:db/id (tempids -3)
:parent/children [[(tempids -1) 0]
[(tempids -2) 1]]}
{:db/id (tempids -4)
:parent/children [[(tempids -1) 1]
[(tempids -2) 0]]}])
(d/q (template
[:find ?parent ?parent-name ?child-name ?position
:where
[?parent :parent/name ?parent-name]
[?parent :parent/children ?children]
[(untuple ?children) [?child ?position]]
[?child :child/name ?child-name]])
@conn))from datalevin.
garrett-hopper
commented on June 9, 2024
The desired code without the workaround would be this:
(let [schema {:parent/children {:db/valueType :db.type/tuple
:db/tupleTypes [:db.type/ref :db.type/long]
:db/cardinality :db.cardinality/many}
:parent/name {:db/valueType :db.type/string
:db/unique :db.unique/identity}
:child/name {:db/valueType :db.type/string
:db/unique :db.unique/identity}}
conn (d/create-conn nil schema)]
(d/transact! conn [{:db/id -1
:child/name "Child 1"}
{:db/id -2
:child/name "Child 2"}
{:db/id -3
:parent/name "Parent 1"
:parent/children [[-1 0]
[-2 1]]}
{:db/id -4
:parent/name "Parent 2"
:parent/children [[-1 1]
[-2 0]]}])
(d/q (template
[:find ?parent ?parent-name ?child-name ?position
:where
[?parent :parent/name ?parent-name]
[?parent :parent/children ?children]
[(untuple ?children) [?child ?position]]
[?child :child/name ?child-name]])
@conn))from datalevin.
garrett-hopper
commented on June 9, 2024
untuple is just an alias for identity (built_ins.cljc#L132), therefore identity could be used in its place for the same purpose. (Though untuple does signal intent better)
Using one or the other is required because destructuring is only supported in clauses that are function calls. (You can't destructure a tuple in a pattern matching clause.)
Also, homogenous tuples can be destructured using ...
E.g.
[?e :tuple ?tuple]
[(untuple ?tuple) [?x ...]]In which case ?x will be bound to each item in ?tuple as expected.
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