> Datomic Pro is issued with a perpetual license, with ongoing maintenance fees of $5,000 per year per system. (source: http://www.datomic.com/get-datomic.html) What is the definition of "system" in this context?

@sova

(let [db (d/db conn)
      blurb-ids  (d/q '[:find [?blurb ...] :in $ :where
                        [?blurb :blurb/attr-only-asserted-when-created]]
                      (d/since db #inst "24 hours ago"))]
  (d/pull-many db '[*] blurb-ids))

no need to use d/log at all. just query a database that only has datoms from the period you care about.

you don’t need to use datalog either:

(->> :blurb/attr-only-asserted-when-created
     (d/datoms (d/since db #inst "24 hours ago") :aevt)
     seq
     (map :e)
     (d/pull-many db '[*])

note that we only use the time-constrained database for the initial seek; the ‘now’ db for the rest, because you may want to query for things asserted in the past (e.g. relationships to previously existing entities, like author etc)

potentially dumb question, but how would i construct a :where so that i can pass a sequence of potential values something can match?

e.g. a list of entity ids

@thedavidmeister

(q '[:find [?e ...] :in $ [?x ...] :where [?e :foo/bar ?x]]
  db xs)

@misha with the ...?

[?x ...] instead of just ?x

kk 1 sec, i'll try that out 🙂

cool

@misha thanks

http://docs.datomic.com/query.html#sec-5-7-2

so is ... some clojure syntax i haven't learned yet?

it is a part of a query grammar

ah ok, so specific to datomic?

I'd say yes

cool, makes sense

not sure why i couldn't find this before

probably putting the wrong words into google 😛

datomic documentation is a good read

tbh i've read over it a few times on different occassions, but it sinks in better when i have a real problem to solve

@thedavidmeister a slow, careful read of http://docs.datomic.com/query.html will save you a lot of time

@beppu A single production transactor + all associated peers and clients

@robert-stuttaford Beautiful. Thank you kindly. So the first step asks the query over a specific time-constrained db, and the second uses that info against the Now version to get all the good stuff, if I'm understanding correctly.

precisely @sova

@marshall that still covers several transactors working in a HA setup, right?

Yes. single production transactor You can, of course, also have an HA transactor for that prod system and as many dev/staging/testing instances as you require

Is it possible with datomic/q to “map” a pull expression over multiple entities in a single query?

@jfntn yes: http://docs.datomic.com/query.html#pull-expressions

there is also d/pull-many for use outside queries

(I am not sure why this exists vs just d/pull with map. Maybe it can be more efficient?)

Also not documented for some reason is that the pull find expression can take a database, (pull $ ?e [:pull-expr])

Ok that worked, thank you @favila

Since you mentioned it, I don't understand the need for the explicit db binding in declarative queries?

if you have more than one database @jfntn

@jfntn Example: (d/q '[:find [(pull $b ?e [*]) ...] :in $a $b :where [$a _ :some-attr ?e-id][$b ?e :id-attr ?e-id]] db-a db-b)