releasing Datomock 0.2.0, with support for the Log API: https://github.com/vvvvalvalval/datomock

I’m trying to reuse the rules and failing to produce the most basic working example:

(def rules '[[(doc-is [?x] ?e) [?e :db/doc ?x]]])
(d/q '[:find ?e :in $ % ?x :where [(doc-is ?x ?e)]] db rules “test-doc”)

ok, you’re not supposed to put the rule invocation inside square brackets - problem solved!

@dm3 paste full solution here, please

(d/q '[:find ?e :in $ % ?x :where (doc-is ?x ?e)] db rules “test-doc

I have a question connecting datomic console to a production database

We are running on cassandra and I was trying to forward port 9042 to a local port and have console connect to datomic:

it seems this connection works, but as soon as you select a database Artemis will throw a ActiveMQNotConnectedException[errorType=NOT_CONNECTED message=AMQ119007: Cannot connect to server(s). Tried with all available servers.]

Is there a simple way to restrict a variable in a datalog query to all entities that are (or are not) referenced by any other entities, via any attribute?

How could I possibly solve this? Which connection is failing? From the transactor to the localhost? Or the other way around?

I assume it's from localhost to the transactor, but how does cassandra store the transactor's address?

is it an IP? a hostname?

@stijn The peer connects to cassandra storage

Cassandra storage has written into it two transactor addresses, as provided by your transactor.properties file

The peer then pulls those and uses them to connect to the transactor

So you need to make sure those hosts are correctly resolveable from wherever you are

the 'host' and 'alt-host' field?

(whereever your peer is)

yes

cool, that should be doable with /etc/hosts 🙂

thanks a lot @favila

@val_waeselynck sorry i missed your message yesterday. Do you have a small repro?

are you seeing a potential leak?

@donaldball

(d/q '[:find ?e
       :where
       [?vt :db/ident :db.type/ref]
       [?a :db/valueType ?vt]
       [_ ?a ?e]])

@donaldball you could put in a clause with the entity ID of your entity of interest in the v position

ah. welp, @favila beat me to it 🙂

@donaldball or use (into #{} (map :v) (d/seek-datoms :vaet)) to get all referenced entities

Getting the opposite (not-reference entities) is harder

mostly because entities don't exist

not-join with your 3 clauses above ?

oh, sorry, all entities

yeah that’s harder

You need to refine what you mean by "not referenced entities"

because theoretically that is any integer

Maybe you mean "any entity which has other assertions on it, but which is not referenced by other assertions"

I think this would do it, but I'm not sure it would run:

[:find ?e
       :where
       [?vt :db/ident :db.type/ref]
       [?a :db/valueType ?vt]
       (not [_ ?a ?e])
       [?e]

I suppose I mean “there do not exist any datoms in the current database which have attributes which are references to the datom in question"

attributes? you mean values?

… yes

Sorry, I haven’t quite gotten the datomic language fully integrated yet 😛

[?vt :db/ident :db.type/ref]
       [?a :db/valueType ?vt]
       (not [_ ?a ?e])

If you want all unreferenced entities, you may not be able to query in a sensible amount of time in a query (you will need a table scan, and the query engine will not allow that)

@donaldball OK I think this will do it efficiently:

(let [partition-key-by (fn [f]
                         (fn [xf]
                           (let [last (volatile! (Object.))]
                             (fn
                               ([] (xf))
                               ([r] (vreset! last nil) (xf r))
                               ([r x]
                                (let [k (f x)]
                                  (if (= k @last)
                                    r
                                    (do
                                      (vreset! last k)
                                      (xf r k)))))))))]
  (->> (sequence
         (comp
           (partition-key-by :e)
           (remove #(first (d/seek-datoms db :vaet %))))
         (d/datoms db :eavt))
;;; just so we don't explode
       (take 10)))

with the 0.9.5530 peer server/clojure client, I’m getting an error {:datomic.client-spi/request-id 782ba011-a723-4f9e-b25c-93338d389785, :cognitect.anomalies/category :cognitect.anomalies/incorrect, :cognitect.anomalies/message :db.error/tempid-not-an-entity tempid used only as value in transaction, :dbs [{:database-id datomic:, :t 137256, :next-t 137258, :history false}]}, but this same transaction succeeds for me using an in-memory database

I get failures with dev storage and dynamodb

csm: using strings as tempids?

yes

I think upgrading to 5544 has the fix. Check out this thread https://groups.google.com/forum/#!topic/datomic/m6vSa6CjqjQ

aha, nice. Thanks!

Hi everyone, I'm doing something interesting that uses time-querying. Basically, I want to know the users username when they posted a thing

since they can change their username (but never their email) i want to find out what they had their username set to at the time of posting

to stay historically consistent

firstly, thoughts? should i even bother? i think it's a cool feature, and an interesting practical use of datomic's capabilities...

secondly, if i were to do this, how do I query for it ? get the creation date of the item, query for the user's username at that db instant, and synthesize them, i think it's a winning approach...