I don't know what datomic uses, but auto scaling groups are part of ec2, not the auto scaling service, afaik.

Right, perhaps I'm reading the marketplace details wrong. here's what it says:

Required AWS Services: APPLICATIONAUTOSCALING, AUTOSCALING, CLOUDFORMATION, CODEDEPLOY, DYNAMODB, EC2, EFS, ELASTICLOADBALANCINGV2, IAM, LAMBDA, LOGS, ROUTE53, S3

I guess it uses it then...

I might be wrong about auto scaling anyway 😊

Amazon EC2 Auto Scaling has moved You have several options for scaling with AWS. Do you only need to manage Amazon EC2 instances?

It's probably there for dynamodb scaling

@U055DUUFS you should be able to use ap-southeast-2 with the 409-8407 release. I will check into what is happening on the marketplace page.

Thanks @U072WS7PE. Look forward to trying it out.

@U055DUUFS Where were you not seeing Ap-southeast-2? I checked on marketplace and was able to see the region when I had 409 selected…

https://previews.dropbox.com/p/thumb/AAIq-zqGVYA_ZxPQjxuSY-HLRBXZInM95Pv6zcJTLDG6Pcug8XBSh-QUGC7DpOFkU8Kw8fooc_2HopiEDpqXoZnaI4l94NnYUoOC8PK2AlKv1_Ox3kuBpHU5u7l1JYnPcJiyPlXFDftRYwJv1wCeetTRBcEHZwk2DMiWpxHgVf4Hp7RJv9Rqll1L8dRZzL3AqFcrCTp3cncmIdOIAfvWh1xVGC9VC6zip6FjbkJkl3EEXw/p.png?size=800x600&size_mode=3

Sounds like I got punked by "estimating your costs" here https://aws.amazon.com/marketplace/pp/prodview-otb76awcrb7aa

Works like a charm.

hi @U06B8J0AJ, pull is a convenience over query, you can always do what you want with a query.

This gets asked a lot, it may be worth it to add pull-many just to spare confusion.

I see, thank you. I figured I could probably create my own pull-many, but I saw it in an example and went looking for it. I guess if for nothing else, for backwards compatibility with existing guides that may be out there, it might be good to have it in.

yeah, you are right 🙂. Hypothetically, I use datomic for newborns registry at a hospital. I assert an entity with :name and :born-at. What is the most idiomatic way to answer what was the name of the last newborn?

ah ok.. That’s clearer. So you want the ‘domain’ most recent time, not the ‘system’ time when the transaction took place. There may be a more idiomatic approach, but right off the top of my head, you can just do a :find (max ?ba) :where [ .. :born-at ?ba] ... then use that value to query for the entity you want

yeah, that was my initial idea. “My idea is to add :created-at and use max on it”. Should be more clear next time 🙂

but anyway seems strange, with SQL semantics is like ORDER BY LIMIT 1… maybe I should look also into raw indexes…

If you want to be really efficient, you should store the reverse index of what you want

Eg if you care about “newest” timestamp, store an attr with the negated ms value

Then it’s always first item in d/datoms

Datomic doesn’t have efficient reverse walking of its indexes, so even if you use raw indexes you will have to do some array bisection to find the last value

interesting approach, thank you!

but I see this pattern quite often: latest news, most recent posts, most liked comments… is datomic a good fit in this case? Or should I use third party indexing tools?

Not a good fit for a naive implementation, which is why it’s even a bit difficult to express succinctly in datalog

There’s lots you can do short of an external index, but if you can’t afford an index scan you do need to do something

Eg you could make a derived attr that orders more naturally; you could cache your “top x” list; you could read the Tx queue and keep the “top x” values incrementally in memory; you could write a bisection algorithm that uses index-scan to find the latest values without a full scan

thank you, do you know some useful resources where I can dig into this topic?

Does Datomic Cloud support DB functions yet?