hi, I do a lot of dynamic queries such as let [ where (into [] (concat (conditions table-namespace-alias auth-path) ;; [?id ?field] [(list rule-name rule-variable '?user-id)])) query {:find [(list 'pull id-field-variable pattern)] :in (if has-ids? ['$ '% '?field pattern [id-field-variable '...] '?user-id] '[$ % ?field pattern ?user-id]) :where where}]

Sorry, I am on my phone but I guess you'll see how I pass the pattern to the pull part of the query

So maybe I'm just not quoting liberally enough…

This is how I pass some params

rules) ] (->> (apply d/q query (if has-ids? [db rules id-field pattern ids user-id] [db rules id-field pattern user-id])) (mapv first)))))

Yes, maybe

Is there any way to get Datomic to output what it ultimately thinks is the query (instead of executing it)?

I think I'm finally getting it. Thanks for the example!

(let [pull-expr [:id :name]
        query (apply-template
                '[common-pull]
                '[:find (pull ?parent common-pull) (pull ?child common-pull)
                  :in $
                  :where
                  [?parent :id _]
                  [?child :parent ?parent]]
                [pull-expr])]
    (d/q query db))

we use this for composing the read part of queries and rules for composing the where part of queries. works well

(def ^:const country-pattern
    '{:country/display-name
      [:alias/name]
      :country/region
      [:region/name
       {:region/_sub-regions
        [:region/name
         {:region/_sub-regions
          [:region/name]}]}]})

  (def ^:const post-location-pattern
    (let [city-and-country-pattern (merge `{:city/country
                                            [:country/name
                                             ~country-pattern]}
                                          country-pattern)]
      `[:city/name
        :country/name
        ~city-and-country-pattern]))

Here's where I'm headed. Just having to be careful on quoting and how I compose everything.

(The queries I'm working on don't need support for runtime variability at this point.)

https://docs.datomic.com/pro/operation/monitoring.html#custom

There’s a metric named “Memcache” which tells you number of requests and the hitrate on both transactors and peer

And also MemcachedPutMsec and MemcachePutFailedMsec

On a fresh peer you can also try d/q with an io context set https://docs.datomic.com/cloud/api/io-stats.html#query and see if any memcache keys are in the :reads map

If your object cache is big enough and you index infrequently, it may very well be that no reads happen from memcached, only writes.

Was about to post that I already checked cloudwatch but couldn't find those metrics (can see other transactor metrics). I too was suspecting it might be that memcached wasn't even required, I just have ~600 datoms (just trying out on-prem) which would trivially fit in the object cache. But wouldn't datomic try to connect to memcached at all? Asking because the active connections on my elasticache memcached node is 0. (I'm able to telnet to memcached from the peer/transactor node)