Clojurians Log v2

Hello ! I have a 3 questions about sorting. There is a fairly large collection of photos, each photo has a ‘photo/taken-at’ attribute with value type instant. I want to retrieve 100 photos ordered by taken-at potentially in reverse chronology. What is the idiomatic way to achieve that ? So far I’ve managed to do it using ‘index-pull’ which also has offset, limit and reverse options. Is this the way to do it ? Then, if I want to find a specific photo title in the oldest 100 photos, I would first retrieve the ids using index-pull, then perform a parameterized :find using those ids and the substring as parameters to the query. Alternatively, if I want to find the title in all photos, I first perform the query, then do a sort-by :taken-at on the results. So 3 questions really, but all related :). Is my thinking correct? Thank you !

i've changed the ident name of the attribute below, but other than that it looks like this

#:db{:id          715,
     :ident       :album/artist,
     :valueType   #:db{:id 20, :ident :db.type/ref},
     :cardinality #:db{:id 35, :ident :db.cardinality/one},
     :doc         "A reference to the artist of an album"}

i don't know if it's related but 715 in my original post would have likely been pointing to a composite tuple entity with a uniqueness constraint by identity

1. Can't claim to vouch for a huge user base, but I'd say that is indeed idiomatic. A good choice, at any rate.

2. That should work. I guess you could also just add the photo title to the :selector and filter "by hand".

3. Again, I think you could just add the photo title to the :selector instead?

@jeroen.dejong If you pass in sets of eids instead of lookup refs it appears to do what you're after.

(d/q {:query '{:find [(pull ?parent [:person/name]) (pull ?child [:person/name])]
               :in   [$ [?parent ...] [?child ...]]
               :where [[?child :person/parent ?parent]]}
      :args  [(d/db conn)
              (into #{}
                    (map #(->> % (d/pull (d/db conn) [:db/id] ) :db/id)
                         #{[:person/name "pete"]}))
              (into #{}
                    (map #(->> % (d/pull (d/db conn) [:db/id] ) :db/id)
                         #{[:person/name "frank"]}))]})
;; Returns
;; => [[#:person{:name "pete"} #:person{:name "frank"}]]

Nice! I guess I can also use datomic.api/entid in the query to resolve the lookup refs. I initially expected both collection bindings to resolve the lookup refs, but it seems to do 1 collection at most. Is that intended?

I'll be creating an internal story to investigate this more deeply but for now you should consider it expected behavior.

In the old or the new db?

this is all in the old db before we get to the part of replaying the tx in the new db

@joshkh Is this on dev-local, cloud, on-prem? Can you send back a report of running: 1. (d/pull (d/db conn) '[*] 69269232556469022) 2. (d/pull (d/as-of (d/db conn) 64288) '[*] 69269232556469022) 3. (d/pull (d/as-of (d/db conn) 64289) '[*] 69269232556469022) 4. (d/pull (d/as-of (d/db conn) 64290) '[*] 69269232556469022) 5. (d/pull (d/as-of (d/db conn) 64291) '[*] 69269232556469022) You can dm me or send this to support.