Erm. That seems like it should work. Let me look into it

in my specific use-case, i think i can use a keyword instead of a ref, but it still looks like a bug and i suspect there are legitimate use-cases which might want to do this

hmmm... im still not sure about how the lookup-ref should look like 😕 im getting this error, when I'm trying to transact:

{:txn/id txn-id
 :txn/matches [[:rule/algo+expr [:regex expr]]]}

Execution error (Exceptions$IllegalArgumentExceptionInfo) at datomic.error/arg (error.clj:79).
:db.error/not-an-entity Unable to resolve entity: [:rule/algo+expr [:regex "XXXX"]] in datom [-9223301668109555930 :txn/matches [:rule/algo+expr [:regex "XXXX"]]]

where :txn/matches is

{:db/ident       :txn/matches
    :db/valueType   :db.type/ref
    :db/cardinality :db.cardinality/many}

lookup ref works when using the datom style:

(tx [[:db/add "x" :txn/id 1]
       [:db/add "x" :txn/matches [:rule/algo+expr [:regex "XXX"]]]])

(tx [{:txn/id      1
        :txn/matches [:rule/algo+expr [:regex "XXX"]]}])

(at least when the tuple attr's 1st element is a keyword, not a ref)

for the card-many you need an extra [] around it

hm. or maybe not

whats’ the schema definition of :rule/algo+expr

{:db/ident       :rule/algo+expr
    :db/valueType   :db.type/tuple
    :db/tupleAttrs  [:rule/algo :rule/expr]
    :db/unique      :db.unique/identity
    :db/cardinality :db.cardinality/one}

and yes, i've tried with and without and extra bracket and it works both ways when using entity-map style and only works without when using datom-style, which is quite logical

right

Well, that's not exactly true anymore bc of tuples

ok, then i understood it correctly

I have asked Cognitect regarding this issue. The answer was that they don’t plan to add features to the free edition at the moment.

You can use the Starter Edition, which is also free.

sure, it's just a bit more troublesome to download for a team, which is just about to learn datomic aaand clojure at the same time... from me...

I know and I also don’t like it. It would be good to write a mail to <mailto:[email protected]|[email protected]>, explaining your situation. Doing so may help to change things.

What would you propose as an alternative? I'm not sure how could the situation be improved. It's an awesome technology, so I understand why Cognitect is keeping it on a short leash... The client lib is downloadable without hassle at least.

I would be happy with the free version too, btw, but since I've diligently read thru the last 3 years of changelogs and learnt about the tuple support, now I want it badly :) But I guess I might just step back a bit and use txn functions to implement composite keys, like 3 years ago...

Without free edition makes harder to have awesome tools like https://github.com/vvvvalvalval/datomock and https://github.com/ComputeSoftware/datomic-client-memdb Also harder to convince people to use/learn it. It goes from "way easier to configure then SQL: just add the dependency and use it" to "oh you will need to crete a account, add a custom repo and it's credentials. You cannot commit your credential. Then you will have access to one year of updates"... 😞

Which process - I guess - acts as a filter or throttle and only seriously interested ppl bother with using Datomic

I agree, it's a pity, but I'm still very grateful that Datomic exists at all :)

I was also pleased to see that tools.deps takes the ~/.m2/settings.xml file into account and it's even explained how to separate your login credentials from the per-project maven repo settings in your deps.edn

All this info is a little too scattered and requires a lot of background knowledge and I feel bad about it, because I have to explain all these quirks to my colleagues too. I'm sure they will ask "how am i supposed to discover all this on my own" and they will feel insecure if I have to tell them that they indeed would have a hard time doing this alone...

Im planning to have datascript around too, so they can quickly experiment, but I'm not sure how different is it from Datomic, coz I never used it...

Datascript had used datomic-free to check if it implement's some features/behavior close to datomic unfortunately it can't be done with new datomic features... non-free datomic is about kill it's small community 😞 (yes, I as previously peer and now a cloud consumer REALLY sad with it)

why so sad about the cloud version?

Despite working in a prime region of a Brazilian capital, I have many issues with my(all available in my region) ISP. I already lost many days of work due no-internet-connection at the beginning of my current project, i used datomic-client-memdb to work offline and datomock to create/reuse test cenarios After the last datomic update, everything was broken. I needed to re-write my test cenarios and I'm unable to work offline Also, moving from datomic-client-memdb to "client proxy", my deftest goes from 0.1ms to 10s. "run all tests" from 1m to 10m (and it FAIL when my internet goes down)

@onetom have you researched datahike? This might be a good middle-ground for your students. https://github.com/replikativ/datahike I’ve been considering switching to it myself for all the same pains that @U2J4FRT2T is feeling, and the fact that it’s open source. Datomic appears entirely uninterested in fostering a community, and so my long-term bet is on something like datahike.

No, I have not encountered datahike yet. Thx for putting it on my radar! I also have issues with my internet connectivity (I live on Lamma island in Hong Kong and only get a 0.5-3Mbit/s usually)...

This issue is also known. The last update to the free edition is about one year old.

regardless, thank you for strangeloop! i've learnt immense amounts from it.

[(tuple ?a ?b ?c) ?datom] [(valid? $ ?a ?b ?c)] Not sure about performance

Ah tuple, I kept trying to destructure with []. Still running into this tho:

"[?a ?v ?e] not bound in expression clause: [(tuple ?e ?a ?v) ?datom]"

tuple is a new feature from datomic. from the last release

[(valid? $ ?datom)] *

Thanks @U2J4FRT2T, I got a few queries working. You can actually bind the tuple components first before aggregating them, which allows for unification to work in both directions, e.g.

:in $ % ?user
:where
[?e ?a ?v ?tx ?op]
[(tuple ?e ?a ?v ?tx ?op) ?datom]
(authorized? ?datom ?user)

you can use [?a :db/ident] to avoid "full db scan" error

another option is d/datoms with a bounded-count for this simple case, anything harder needs a subquery because you cannot perform aggregation before the :find stage