Simplest example: :entity/state is a keyword

[:find ?e :where [?e :entity/state :pending]]

[:find ?e :where [?e :entity/state ":pending"]]

[:find ?e :where [?e :entity/state "pending"]]

I have a question. Say I want to express the equivalent of this (pseudo?) SQL query in Datomic/datalog:

SELECT author.name, count(*) AS num_books
  FROM author
  JOIN book
    ON author.id = book.author_id
  GROUP BY author.id
  HAVING num_books >= 5

@slpssm third one if it ever worked was a bug. Second one is I think a concession to Java users of the API

[:find (pull ?aid [:author/name]) (count ?bid) :where [?aid :author/books ?bid]] @jeff.terrell

There is any way to specify :db/txInstant while import data pipelining? Datomic tx must ensure (:db/txInstant early-tx) <= (:db/txInstant later-tx), howerver, pipelining can’t ensure the ordering of imports.

@jeff.terrell you're correct about the peer library. All query engines need their working set in memory 🙂

I somehow managed to miss the existence of the client library

@jeff.terrell The approach would be essentially the same with the client - the difference is that the work would happen on the peer server instead of in your process

You’d still do the “limit by > 5” in your app

using something like the query @favila posted aboe

above*

Incidentally, since the client will return results in a channel, I’d do the filtering with a transducer

@marshall - OK. I think that's about what I expected. Thanks for confirming. Now, if there was a long tail, with lots of results < 5, I'd be wasting a lot of bandwidth, right? Is there a simple way to avoid that? Maybe ship the filter up to the server side, somehow?

If this were SQL and I was trying to limit results somehow in a way that wasn't supported by SQL, I'd reach for a database function.

TBD 🙂 Sort in the peer server + limit/offset - which I believe is a request in our customer feedback portal

you should vote for it 🙂 or if it’s not there, you should add it

OK! :-)

@isaac pipelining does not necessitate out of order

@marshall - I think the feature I want to suggest is "custom server-side database functions to limit or transform results server-side when using the client library". Does that sound like a reasonable request to you, or would that be a bad idea for any reason that you can see?

When I am trying to suggest features - it stays on the account page and just adds “#”

http://api.eu-west-1.receptive.io/widget/ping Failed to load resource: the server responded with a status of 400 (Bad Request) Also I have this error, is this connected?

@marshall

It worked for me, @kirill.salykin.

but doesnt work for me

@kirill.salykin Are you running any ad blockers or ghostery or anything like that?

I disabled AdBlock

still same

depending on config they can prevent external redirects

hrm. what browser?

chrome and safari

will try Firefox

weird. i wonder if there’s a system firewall issue

possible…

sounds like you’re not getting content from receptive

receptive responses with “{”message”:“invalid user”}”

yeah, i just verified it works ok for me in chrome

let’s go to a private chat

sure

heh. for those of you awaiting updates with baited breath about Kirill’s plight in accessing the feature portal - software is hard, integrating multiple softwares is harder 🙂

@favila It’s just keep ordering of returning, not guarantee order of executing.

how to modify this query: ‘[:find ?name ?filter :where [?e :part/name ?name] [?e :part/filter ?filter]] so it returns […] for ?filter? :part/filter is a many keywords type, but above query returns only first keyword from collection …

got it somehow working like that: (d/q ‘[:find ?name (distinct ?filter) :where [?e :part/name ?name] [?e :part/filter ?filter]] (d/db (d/connect database-uri)))

but i feel i am missing something… ;/

@isaac using the impl of pipelining in the docs, yes. But within a process you are guaranteed that order of d/transact call is order of execution

So with an implementation of pipeline that calls d/transact in correct order you know they will run in correct order

@isaac eg https://gist.github.com/favila/3bc6fae005228a3290d5509c088e2f11

I also wrote one (less elegant) that didn't use core async, used reduction, kept inflights in an accumulating vector, and did "gc" of inflight futures when the vector reached capacity

the advantage of it was it didn't run any additional threads

You mean, the d/transact-async is keep ordering of executions same with ordering of invokates?

@favila

@isaac yes

the problem with the pipelining code in the docs is core.async/pipeline does not preserve order of invocation because it uses a threadpool

(it's not immediately obvious that it does this)

datomic.api is not open source, and the docs has no instructions about this

Anyway, it’s a good feature, thanks, @favila

You are talking about this pipeline code? http://docs.datomic.com/best-practices.html#pipeline-transactions

yeah

core.async/pipeline-blocking doesn't run input "tasks" in-order because it runs them in parallel on a threadpool

so which runs first is up to chance

(this code is open)

but d/transact-async etc send transactions to the transactor in the order they are invoked

so you could just (doseq [tx txs] @(d/transact-async conn tx))

“but d/transact-async etc send transactions to the transactor in the order they are invoked” it is key point

except that the flood of transactions would kill the transactor

well, not kill it, but the transactors would be unresponsive

it would eventually curn through them all

the pipelining code is just to ensure queue depth

is reasonable

well, thanks for you hints, let my try your code. 🙂

is there any work on client api libraries for non jvm languages taking place yet?

can a transactor support multiple databases? If not, how would you test using multiple databases on a localhost environment?