mpdairy/posh

A luxuriously simple and powerful way to make front-ends with DataScript and Reagent in Clojure.

Christopher Small

@metasoarous

The graph structure has a cache of active queries, and on transaction, it goes through all the queries and runs a pattern match against the cached structure, and decides whether to rerun the actual query. I don't recall the details of how things are structured though.

If you do some pprints as things flow through, you should get a better sense though.

Brian Marco

@bamarco

That sounds like I could then. I want to stop all the listener business and subsume that into the compute graph. And I might be able to pass the cache as a value too if I can't drop it entirely. Not sure if it's worth the time at this phase.

javier abanses

@nrfm

@mpdairy thanks!

Baruch Berger

@bbss

I'm trying out posh, but getting an error when using pull:

plugin_base.cljc:77 Uncaught TypeError: Cannot read property 'call' of null
    at posh$plugin_base$get_db (plugin_base.cljc:77)
    at Function.posh.plugin_base.pull.cljs$core$IFn$_invoke$arity$5 (plugin_base.cljc:127)
    at posh$plugin_base$pull (plugin_base.cljc:123)
    at Function.posh.plugin_base.pull.cljs$core$IFn$_invoke$arity$4 (plugin_base.cljc:136)
    at G__10150__3 (core.cljs:4148)
    at G__10150 (core.cljs:4149)

maybe this warning I get during compilation has something to do with it:

WARNING: Wrong number of args (1) passed to posh.plugin-base/missing-pull-result at line 20 resources/public/js/compiled/devcards_out/posh/plugin_base.cljc
WARNING: Wrong number of args (1) passed to posh.plugin-base/missing-pull-result at line 22 resources/public/js/compiled/devcards_out/posh/plugin_base.cljc
WARNING: Wrong number of args (1) passed to posh.plugin-base/get-db at line 127 resources/public/js/compiled/devcards_out/posh/plugin_base.cljc

Brian Marco

@bamarco

@bbss Can you show your call to pull in your code and your ns?

Baruch Berger

@bbss

@bamarco sure, thanks

(ns korean.cljs.quick-word
  (:require
   [korean.cljs.training.training-component :refer [typing-field matched-text]]
   [datascript.core :as d]
   [reagent.core :refer [as-element] :as r]
   [posh.reagent :refer [pull q posh! transact!]]
   [cljs-react-material-ui.reagent :as ui]
   [cljs-react-material-ui.core :refer [get-mui-theme]]
   [cljs-react-material-ui.icons :as ic])
  (:require-macros
   [devcards.core :as dc :refer [defcard deftest]]))


(defn quick-word-component
  [state db]
  (let [current-typed (r/atom "")
        results (r/atom {})
        challenge (next-challenge (expression-couples-by-levels db))
        show-tip (r/atom false)
        [from to] (first challenge)
        from-text (:expression/korean (pull @db '[:expression/korean] from))
        to-text (:expression/english (pull @db '[:expression/english] to))]
    [:div ..etc..]))

Baruch Berger

@bbss

and

(def db
  (d/create-conn {:translated/english {:db/cardinality :db.cardinality/many
                                       :db/valueType :db.type/ref}
                  :translated/korean {:db/cardinality :db.cardinality/many
                                      :db/valueType :db.type/ref}}))
(posh! db)

for what it's worth. That doesn't throw though.

Brian Marco

@bamarco

@bbss posh calls to pull and q take the whole conn not just the db. Try removing the derefs. So it says db instead of @db

Baruch Berger

@bbss

@bamarco yes, forgot to change it back, I tried like that initally. Same problem.

Brian Marco

@bamarco

@bbss You also need to 'deref' the pull call itself. So @(pull ...)

Baruch Berger

@bbss

well the error already occurs when calling pull

Brian Marco

@bamarco

Do you have a pull by itself? Because you are immediately calling a keyword property on the result.

Baruch Berger

@bbss

no, the pull didn't succeed, this would work with a normal pull though.

Brian Marco

@bamarco

Posh pull returns a ratom not an entity.

Baruch Berger

@bbss

yes, I understand that. But posh pull is the thing that errors so we aren't there yet :D

Baruch Berger

@bbss

but your point about taking the conn, not just db makes me think maybe it's got something to do with devcards

Brian Marco

@bamarco

That's all I got. Good luck though. :smile:

Baruch Berger

@bbss

Okay, thanks for the input :D

posh looks pretty awesome :)

was doing a kind of full rerender approach before, but I think reactive q and pulls will be a lot cleaner/faster

Brian Marco

@bamarco

Yeah, it def cuts down on reloads.

Baruch Berger

@bbss

Hmm, I don't get the same error anymore. I think it's because of the order in which I required..

λex Vincent

@alexisvincent

Hi guys :D Awesome awesome lib. Was wondering how you managed to extract datoms relevant to a query? I can’t seem to find a way to do it and cant quite grok where its happening in the posh codebase

Matt Parker

@mpdairy

hi @alexisvincent thanks! I don't remember exactly, but basically I had to come up with a bunch of rules for various scenarios in q. A simple case would be where q is looking for [?e :some/attrib ?v], then you just look for anytime any transaction with :some/attrib occurs. The functions for figuring this out are insrc/posh/lib/q_analyze.cljc. The simpler version is called pattern-from-eav--old, which is more easy to understand but generates patterns that are much less specific than the query. ("eav" is an entity-attrib-value rule). The more complex function is called pattern-from-eav and unfortunately it worked really well until we found out it missed one common case, which I couldn't figure out how to fix, so posh is just using the simpler one for now.

λex Vincent

@alexisvincent

@mpdairy Thanks! Although I’m particularly interested in extraction at query time. So how do you retrieve the initial set of datoms? Trying to work out if a similar aproach can be used to get initial datoms from a datomic database for sync

Matt Parker

@mpdairy

@alexisvincent Oh yes you could use that initial set of datoms to sync with datomic. if you call q-analyze with the :datoms flag you'll get a list of all the relevant datoms for a query, which you could run on the datomic db and then just send all the datoms over to datascript. How the :datoms thing works, if I remember correctly, is the original query is changed so that instead of returning the stuff specified in the :find of the q query, it just returns all possible combinations of the ? query vars in the :where eav rules. Then to construct the datoms, it goes through all query eav rules and replaces all the ? vars with every possible combos.

to get the actual query results with the :find constraints, it just runs q on the set of possible vars (not the whole db), so it should still be pretty fast

λex Vincent

@alexisvincent

Hmm. That’s clever! Thought you might have figured out a way to it with one query. Pull is a bit more complicated though..? I was wondering about an approach that constructed a filter database specifically for the query and then just saved Datoms it encountered to a set

The catch set might be too large though

Matt Parker

@mpdairy

I think with pulls all the relevant datom info is already in the result of the pull results, so you just have to traverse it and pull out everything as individual EAV datoms.

Have you looked at the Datsync project? They've been working on syncing between datomic and datascript for a while now. I don't know how it's going, but they are active at least.

Oliver Rolle

@orolle

@mpdairy Does posh have the same performance characteristics as rum + datascript? I have read that datascript causes lags in the UI when the database is large (browsers UI thread is blocked)? Is it an option to run a datascript query within a web worker?

Matt Parker

@mpdairy

@orolle Posh should be faster because it doesn't make full queries or pulls every time there is a new transaction, only when a new tx will change the result of a pull/query (this is assuming we're comparing it to a rum + raw datascript that redoes all its pulls/queries every tx). In posh, pull is more efficient than q, so you might be able to get away with a large ui if you use mostly pulls.

i'd just recommend doing some testing before you commit to using it

Oliver Rolle

@orolle

@mpdairy Thanks. I will try it out.

Álvaro Castro-Castilla

@alvatar

Hi @mpdairy, could you provide some pointers on how to use Posh with Rum, please?

Álvaro Castro-Castilla

@alvatar

Seems like this answers my question: mpdairy/posh#27

Camilo Roca

@carocad

hey @mpdairy first of all thanks for the great work that you have done with posh !! that is definitely the missing piece in reactive programming that I was looking for.
I just started working with it and got some errors using pull. I checked the source code and Cursive showed me that there are three functions used with less than their declared arguments; namely

posh.plugin-base/missing-pull-result line 20 and 22
posh.plugin-base/get-db line 127
The error that I get is this

object[TypeError TypeError: null is not an object (evaluating 'new cljs.core.Keyword(null,"conn?","conn?",167224275).cljs$core$IFn$_invoke$arity$1(dcfg).call')]
posh$plugin_base$get_db
cljs$core$IFn$_invoke$arity$5
posh$plugin_base$pull
cljs$core$IFn$_invoke$arity$4
G__10589__3
G__10589


eval code
eval@[native code]
figwheel$client$utils$eval_helper

Since I just started working with posh, I am not sure if this is a problem with my configuration or an actual bug in the implementation, so I wanted to ask you first. I am happy to submit a PR to fix that if you want.

Camilo Roca

@carocad

oh it seems that this was already solved in master: mpdairy/posh@61c951b
I dont see a new release in Clojars, though :(

Petrus Theron

@theronic

Any update on Rum support for Posh? :) Posh is the last thing keeping me on Reagent

Christopher Small

@metasoarous

@theronic I don't think anyone has done this yet, but there was a bunch of refactoring that extracted most of the stateful bits of things so that someone could add a rum plugin fairly easily. If you're interested in hacking on that, I'd be happy to point you in the right direction there.

Brian Marco

@bamarco

@theronic i also put a ticket describing what I think needs to take place to make it happen.

Matt Parker

@mpdairy

does anyone want to help me set up posh to automatically compile and do a new release to clojars whenever master changes? I tried before but I couldn't get the auth working.

Camilo Roca

@carocad

@mpdairy I have an auto deploy config with travis ci for one of my projects. I didnt setup the auto deploy myself but I think that the file is pretty self-explanatory. The only things that you would need to change are the your encripted env vars and your release config in project.clj. Links below

Matt Parker

@mpdairy

@carocad thanks! that's just what I needed

Petrus Theron

@theronic

Is there a Leiningen template for a quick blank reagent+datascript+posh project?

Brian Marco

@bamarco

Best I know of is to use lein new chestnut <app-name> -- --reagent then add the posh depency manually.

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