Can we get when an eid is created using entity ?

Or the only way is to use q and get the :db/txInstant ?

@boldaslove156 unless the entity is a transaction, the latter

thanks! @potetm

how to express a query to find all entities that have the same value for an attribute?

(where that value is left unbound)

@uwo so yo don’t have the value, you just want to find entities that share values for an attribute? you could group entities by values

(->> (group-by :v (seq (d/datoms db :aevt :ns/key)))
     (map (fn [[v datoms]]
            [v (map #(d/entity db (:e %)) datoms)]))
     (into {}))

hehe. I was wondering if this was something that is expressible in datalog. I had thought of just dropping into sequence fns

datalog = bound values. you said not to bind it. [:find ?e ?v :where [?e :attr ?v]] otherwise 😛 group-by ?v ofc

@robert-stuttaford 😄 thanks

so is there anything wrong with this kind of query

[:find ?t1 ?t2 ?y
 :where
 [?e1 :movie/title ?t1]
 [?e1 :movie/year ?y]
 [?e2 :movie/year ?y]
 [?e2 :movie/title ?t2]
 [(not= ?e1 ?e2)]]

not totally getting the point of the query? you want every possible pair of titles in a year?

but yes, the not= (or something like it) is needed to avoid the self-join

you can use != (native operator, not clojure function) and maybe the query engine can use that info

also I would reorder the clauses

put the years first, then the not, then the titles

basically my colleagues are trying to express a query like “find all entities that have the same value for attribute X and different values for attribute Y” and are writing queries like the above

And I’m the colleague 🙂 So imagine you have a bunch of Address entities with city, state, and zip (etc), and you want to query for “Show me all cities with more than one zip code,” how would you query for that?

@uwo there's no check that t1 and t2 differ

two different movies (?e1 ?e2) could be in same year and have same title

you could use aggregation @manutter51

I have a bunch of data which is time-stamped. I want to count every occurance of a data-point, grouped by the day/month of the timestamp. Whats the datalog way to go about that?

sorry, yeah i should have read the example I pasted before hand. my bad

@laujensen http://docs.datomic.com/query.html#with

@marshall, thanks, but how do I got about disregarding all information except date and month ?

ah. they’re separate attributes? you may need to do a custom aggregation

Right. Then when I query [?x ?y] I only get one result and it doesnt allow [?x ?y] ..., or [?x ?y ...]. How do I get a list of filtered results ?

@marshall hi! I have a quick question on Datomic Cloud: will the pricing include a license to use? and around how much it will cost?

@laujensen I'll have to try a couple things. I might do the aggregations in app code and/or use nested or multiple queries depending on the data size. I'll try to get back to you tomorrow

@hmaurer the license is included via purchasing through AWS marketplace. Solo topology will be around $1 a day. That's cost of the AWS infrastructure and the cost for Datomic

Production topology will be more

@marshall that sounds amazing for hobbyists

That's definitely the hope :)