@bkamphaus: thanks, it hadn't occurred to me that component was treated as a technical term before the above two posts. Forgive my mediocrity.

@bkamphaus Does d/with work on as-of db values ?

Can I add a nil attribute value with the map form and expect it not to be asserted at all while the rest of the attributes are?

{:db/id (d/tempid :db.part/user)
 :order/status (get-status)}
;; get-status might return nil

no. you need to exclude it from your transaction

thanks robert

(let [s (get-status)] (cond-> {:db/id (d/tempid :db.part/user)} s (assoc :order/status s)))

you probably aren't doing this, but you can't assert {:db/id ...} without at least one attr along with it

yeah i have a bunch of them

so I'm not the sole inventor of the (cond-> m x (assoc :x x)) pattern. bummer

you bet! rich did that years ago 😉 https://github.com/Datomic/codeq/blame/master/src/datomic/codeq/core.clj#L406

-grin- use the hell out of that pattern

@greywolve: I did an experiment over the weekend using d/with on as-of dbs, and I haven't seen any issues, fwiw

I’ll have to defer to @marshall or @jaret re: anything changing with that behavior, but last I was aware with prospective transactions don’t change what an as-of database will find/retrieve with query, datoms, etc. - the with transaction is filtered out of the as-of db.

@greywolve: @bhagany https://groups.google.com/d/msg/datomic/-gDB2EX7r58/CP2n4GELAgAJ with and as-of should not be used together.

@jaret I saw that, and I was under the impression that that thread applies to doing the reverse

Thanks all 🙂

(d/as-of (d/with …)) does lead to unexpected results

(if you're expecting your d/with stuff to show)

speculative branching (i.e. with) is only allowed on the “current” DB as-of is a filter, so I wouldn’t recommend doing either

huh, okay

Hi, I think I am understanding something wrong in the CORS option of REST APi. Isn’t it the way to specifying all origins allowed, eg, bin/rest -p 8001 -o /'*'/ ddb datomic:<ddb://us-east-1/nameofdynamodatabase>

When you retract an entity related to an isComponent attribute, is the history for that entity lost? I can’t find some of them even with (d/as-of db tx).

Oh. Hm. If a given TX has retracted an attribute, you have to use an earlier “value of the database” to find out what it was.

If that history datom indicates the attribute was “deleted”, then decrement the TX and run the query with the as-of db to find out what it pointed to. Seems to work.

operational question: if you have a transactor running in EC2 and you want to schedule backups of the db, is the best practice to have a separate EC2 instance (or a Lambda function or what have you) with a separate Datomic install and a crontab? My initial thought was to add an /etc/cron.d entry in the CF template but my stumbling block is the fact that the actual install location of …/bin/datomic is not easily found

which makes me suspect that I’m not supposed to use it for anything. 🙂

IMO better to use a separate instance. We use our jenkins for that

@chris_johnson we use a separate t2.medium which runs hourly. i haven't yet figured out how to make it run backups in a loop (start again as soon as you're done). it's NOT recommended to run backups on your transactor machine because of the CPU hit

backups run from storage directly, no need for transactor involvement!

right, I was thinking since we don’t (yet) have anything running but transactors, and since I’m about to push a version update, maybe we could throw the cron job on the machine we have

but I actually reached the same conclusion as you as soon as I read “please give backup as much memory as your transactor usually gets"

our data is small and backups that have been done by hand are pretty snappy, I think I’m going to try doing it in a Lambda function

yeah, not a good idea. too much of a disturbance to transactor process. of course, we did exactly this for the first 18 months, when we ran a snowflake server with transactor, postgres, memcached, backups, and rabbitmq all on one instance 😄

I will let you know how it goes

I’ll just echo the recommendation to use separate instance and have it backup in a loop or at regular (frequent) time intervals.