Is there a list of how database function parameters get converted?

For instance, a clojure set gets quietly converted to a java.util.HashSet. Which was very confusing and broke my function. This is also not documented anywhere. I posted this on the mailing list a few days ago, but it hasn't been published.

@rauh: at present Java collections — java.util.HashSet, java.util.ArrayList, etc. — not documented at present because it falls out of an implementation details. We’re considering whether or not to change the behavior in a future release and will document the boundaries when we make that decision.

definitely understand why it’s surprising at present.

Hi. There may be an obvious question but how do I query only the datoms that were introduced/modified/removed in a specific transaction? I know I can run (let [db (d/db conn)] (d/q ... (d/history db) (d/t->tx (d/basis-t db)))) but then I can't use pull in the query because that doesn't work against the history.

@jannis: you want to do a query against the log, as with the last few examples on this page: http://docs.datomic.com/log.html

is X in the db? - (d/db conn) was X ever in the db? - (d/history db) was X in the db at this time? (as-of filter) did X get added after this point? (since filter) what data was in X transaction (log)

@bkamphaus: Nice summary of scenarios, thanks 🙂

However, I'm testing against an im-memory db, which doesn't have a log.

I guess since would work if there is a simple way to obtain the penultimate transaction.

Something like d/next-t just with previous instead of next.

When testing queries that use the pull syntax I'm assuming I need to create a memory-backed Datomic connection and transact some test fixtures into it?

(Or use d/with.)

zane: 'tis what i do

i don't think d/with will work, as those datasets aren't "proper datomic databases"

not sure I follow what is meant by “those datasets”, d/with returns db-after, db-before etc. and these are database values.

For protecting tests that mutate state from each other's damage we also enjoy: https://github.com/vvvvalvalval/datomock (bonus: our tests run a zillion times faster because we only migrate the test database once at the start of the test runs)

wat?!

(let [test-str (str gensym)] (d/create-database test-str) (d/connect test-str)) ?

(d/transact schema/schema.clj (d/connect test-str))

and if you don't want to do that for each test you can always create-database and delete-database in the test ns fixtures

which is vastly slower but whatever at least you don't have to worry about cross-test state persistence

bkamphaus: i must've misunderstood how d/with works.

@bvulpes: Something like this:

(defn empty-db-with-schema []
  (d/create-database uri)
  (let [conn (d/connect uri)
        db (d/db conn)]
    (d/delete-database uri)
    (d/release conn)
    (-> db
        (d/with schema)
        :db-after)))

If all your tests need to do is query you could call that once and use the returned database value in all of your tests.

If you need to test code that calls d/transact it's another story.

my tests are pretty side-effecty, so i tend to test code that transacts pretty frequently.

Seems like vvvvalvalval/datomock just automates use of d/with.

#nodeps

#nih?

#railslifestyle

there's a pragmatic middle ground.