在单个 datomic 查询中查询多个实体的值 (Roam Alpha Api)

Question

I'd like to in a single datomic/datalog query get output relating to multiple entities

Eg

In my db (querying Roam graph via RoamAlphaApi) for one value ( "YjpbFUsTx" ) I can do this:

[:find ?e ?stri :where [?e :block/uid "YjpbFUsTx"][?e :block/string ?stri]]

gives me

?e	?stri
420	Hello

But I want to pass on two values "YjpbFUsTx" and "TgpgOssBM"

to give me

?e	?stri
420	Hello
624	Perfect

How do I do that?

I've tried several variations but none give any output.

Useful reference: https://www.zsolt.blog/2021/01/Roam-Data-Structure-Query.html .

Answer 1

You can pass collections into a parametrized query. Have a look in the documentation: https://docs.datomic.com/on-prem/best-practices.html#collections-as-inputs

(d/q 
 '[:find ?e ?stri
   :in $ [?uid ...]
   :where 
   [?e :block/uid ?uid]
   [?e :block/string ?stri]]
 db ["YjpbFUsTx" "TgpgOssBM"])

; =>
#{[420 "Hello"][624 "Perfect"]}

---

On another note: I suspect, your :block/uid is a unique identifier? If you have :db/unique :db.unique/identity set for the attribute, you should use d/pull-many in this situation:

(d/pull-many db 
  [:db/id :block/string] 
  [[:block/uid "YjpbFUsTx"] [:block/uid "TgpgOssBM"]])

; =>
[{:db/id 420
  :block/string "Hello"}
 {:db/id 624
  :block/string "Perfect"}]