lilactown/pyramid

A library for storing and querying graph data in Clojure

pyramid's Issues

Relax requirement for collections with lookup refs to be homogeneous

In order to support pulling data from asami, we need the ability to follow references in collections that are heterogeneous, because asami only stores "top level" entities as idents in the tree.

Order is lost when pulling on lists

As discussed on slack.

This appears to be down to the use of into in the list? branch of the visit function.

Improve support for partial data sets

I find myself sometimes working with data that is not entirely complete. For example:

;; OK

(def db (pyramid/db [{:id   0
                      :refs [[:id 1]]}
                     {:id    1
                      :hello :world}]))

(pyramid/pull db [{[:id 0]
                   [{:refs [:id :hello]}]}])

;; => {[:id 0] {:refs [{:id 1, :hello :world}]}}

I.e., I have a number of entities (for example, retrieved from persistent storage), and I'd like to throw them at Pyramid and ask some questions, ad-hoc. This works well, as long as the data set is complete (no dangling idents).

In the following example, it doesn't work as well:

;; Not OK

(def db (pyramid/db [{:id   0
                      :refs [[:id 1] [:id 2]]}
                     {:id    1
                      :hello :world}]))

(pyramid/pull db [{[:id 0]
                   [{:refs [:id :hello]}]}])

;; => Execution error (NullPointerException) at pyramid.pull/visit$fn (pull.cljc:157).

When working with Pathom in a similar scenario, the ident itself will be treated as a minimal entity (i.e., just converted to a map: {:id 2}), with the result of the pull (which may be nil) merged to that map. This guarantees that a minimal result will be returned where data is missing.

The result will be something like:

{[:id 0] {:refs [{:id 1, :hello :world}
                 {:id 2}]}}

What do you think of this?

Delete

Return indices in pull report

Something like

(pull-report db [{:foo {:bar [:baz]}}])
;; => {:data {,,,} :entities #{} :indices #{:foo}}

pull-report

Create a function pull-report which provides a collection containing the queried entities

Reverse order for lists?

Hey @lilactown !

Thanks for this great library.

I was wondering whether lists being reversed was a known/expected behavior or if this could be a bug or misuse on my side:

(let [entity {:id 9
              :my-list [{:thing {:id 1}}  ;; ← vector
                        {:thing {:id 2}}
                        {:thing {:id 3}}]}
      db (pyramid.core/add {} entity)]
  (pyramid.core/pull db [{[:id 9] [:id {:my-list [{:thing [:id]}]}]}]))
;; Order is preserved: {[:id 9] {:id 9, :my-list [{:thing {:id 1}} {:thing {:id 2}} {:thing {:id 3}}]}}


(let [entity {:id 9
              :my-list '({:thing {:id 1}}  ;; ← list
                         {:thing {:id 2}}
                         {:thing {:id 3}})}
      db (pyramid.core/add {} entity)]
  (pyramid.core/pull db [{[:id 9] [:id {:my-list [{:thing [:id]}]}]}]))
;; Reverse order: {[:id 9] {:id 9, :my-list ({:thing {:id 3}} {:thing {:id 2}} {:thing {:id 1}})}}

I noted the README says:

Collections like vectors, sets and lists should not mix entities and non-entities. Collections are recursively walked to find entities.

Could this be the explanation? I'm not sure I fully understand what exactly should be avoided.

Thanks for your time.

Plans for supporting wild card for pulls?

This library looks neat! I was wondering if there are future plans for supporting wild cards for joins similar to https://docs.datomic.com/on-prem/query/pull.html#wildcard-specifications.

I was hoping to be able do something like the following and grab the denormalized view.

(a/pull my-db '[{[:component/id 0] [*]}])

Dynamic map keys

Support something like

(p/pull
  (p/db
    [{:classroom/id "c1" :school [:school/id 1]}
     {:classroom/id "c2" :school [:school/id 1]}
     {:classroom/id "c3" :school [:school/id 2]}
     
     {:school/id 1
      :allocations {[:classroom/id "c1"] [[:course/id 1] [:course/id 2]]
                    [:classroom/id "c2"] [[:course/id 1]]}}
     {:school/id 2
      :allocations {[:classroom/id "c3"] [[:course/id 1] [:course/id 3]]}}

     {:course/id 1 :course/name "A"}
     {:course/id 2 :course/name "B"}
     {:course/id 3 :course/name "C"}])

  [{[:school/id 1] [{:allocations [{???? [:course/name]}]}]}])
;; => {[:school/id 1]
;;     {:allocations
;;      {[:classroom/id "c1"] [#:course{:name "A"} #:course{:name "B"}],
;;       [:classroom/id "c2"] [#:course{:name "A"}]}}}

We'd want to support this for joins and unions.

A few ideas:

1. Use _ as the key, e.g. [{'_ [:course/name]}]
2. Support some kind of regex a la spec, perhaps use spec itself. E.g. [{(s/spec (s/tuple keyword? string?)) [:course/name]}]
3. Accept a predicate fn, such as [{(fn [x] (and (vector? x) (= :classroom/id (first x)))) [:course/name]}]

add-report

Should also report all entities added 😄

Data loss in p/add with nested maps

Hi,
I've noticed that in some cases pyramid normalisation replaces an entity with a reference but losses data of this entity.
Example:

(p/add {} {:a/id 1 :b [{:c {:d/id 1 :d/txt "a"}}]})
=>  #:a{:id
      {1 {:a/id 1, :b [{:c [:d/id 1]}]}}}

Infer EQL query from data

There is a helper function to do this in other libraries like pathom and malli.

Replacing an entity using `delete` and `add` throws exception if entity does not exist

When there is already data in the database, this works:

(-> {}
    (pyr/add {:person/id 2 :person/name "Mark"})
    (pyr/delete [:person/id 2])
    (pyr/add {:person/id 2 :person/name "Will"}))

=> #:person{:id {2 #:person{:id 2, :name "Will"}}}

If one avoids the delete, there is also no issue:

(-> {}
    (pyr/add {:person/id 2 :person/name "Mark"})
    #_(pyr/delete [:person/id 2])
    (pyr/add {:person/id 2 :person/name "Will"}))

=> #:person{:id {2 #:person{:id 2, :name "Will"}}}

But if there is no initial data in the database at all for that entity:

(-> {}
    #_(pyr/add {:person/id 2 :person/name "Mark"})
    (pyr/delete [:person/id 2])
    (pyr/add {:person/id 2 :person/name "Will"}))

Execution error (NullPointerException) at pyramid.core/update-ref (core.cljc:85).
Cannot invoke "clojure.lang.Associative.assoc(Object, Object)" because "em" is null

Of course, it is fine if there is at least one other entity in the database:

(-> {}
    (pyr/add {:person/id 1 :person/name "Mark"})
    (pyr/delete [:person/id 2])
    (pyr/add {:person/id 2 :person/name "Will"}))

=> #:person{:id {1 #:person{:id 1, :name "Mark"}, 2 #:person{:id 2, :name "Will"}}}

`lambdaisland/uri`

I don't know if this is expected behavior or not, but it is an oddity that I encountered:

(pyramid/db [{:my/id  "hello"
              :a-uri  (lambdaisland.uri/uri "http://www.example.com")}])

This expands to,

{:my/id {"hello" {:my/id "hello",
                  :a-uri ([:fragment nil]
                          [:query nil]
                          [:path nil]
                          [:port nil]
                          [:host "www.example.com"]
                          [:password nil]
                          [:user nil]
                          [:scheme "http"])}}}

Rather than the…

{:my/id {"hello" {:my/id "hello",
                  :a-uri #lambdaisland/uri "http://www.example.com"}}}

… one might hope for.

Do you have any guidance as how to deal with a case like this?

Edit: Tracked down and fixed the problem in #18.

Recursive unions

Hi there 👋

I've been tinkering with pyramid in a language project that supports deeply nested logical expressions. Expressions themselves can be either some form of binary expression (e.g. and, or, etc), or a terminal. I've modeled these as two separate entity types.

They normalize just fine, but I'm having troubles pulling the data back out using a "recursive union" query. I've forked and committed a failing test of what I was expecting the output to be. I could very well be doing something obviously wrong here but I can't seem to massage this query into a shape that does what I want...

https://github.com/cjsauer/pyramid/blob/29071e88072737260d46b3d1ddc5310f590a92a1/test/pyramid/core_test.cljc#L294-L320

I'll copy the test here as well:

  (t/testing "recursive union"
    (let [data {:expr/id       0
                :expr/operator :add
                :expr/operands [{:expr/id       1
                                 :expr/operator :mult
                                 :expr/operands [{:term/id    0
                                                  :term/value 42}
                                                 {:term/id    1
                                                  :term/value 100}]}
                                {:expr/id       2
                                 :expr/operator :sub
                                 :expr/operands [{:term/id    3
                                                  :term/value -10}
                                                 {:term/id    4
                                                  :term/value 17}]}]}
          db1 (p/db [data])
          query [{[:expr/id 0] {:expr/id [:expr/operator
                                          {:expr/operands '...}]
                                :term/id [:term/value]}}]]
      (t/is (= {:expr/operator :add
                :expr/operands [{:expr/operator :mult
                                 :expr/operands [{:term/value 42}
                                                 {:term/value 100}]}
                                {:expr/operator :sub
                                 :expr/operands [{:term/value -10}
                                                 {:term/value 17}]}]}
               (get (p/pull db1 query) [:expr/id 0])))))

This results in:

recursive union
Expected:
  {:expr/operator :add,
   :expr/operands
   [{:expr/operator :mult,
     :expr/operands [{:term/value 42} {:term/value 100}]}
    {:expr/operator :sub,
     :expr/operands [{:term/value -10} {:term/value 17}]}]}
Actual:
  {:expr/operator :add, :expr/operands []}
Diff:
  - {:expr/operands
     [{:expr/operator :mult,
       :expr/operands [{:term/value 42} {:term/value 100}]}
      {:expr/operator :sub,
       :expr/operands [{:term/value -10} {:term/value 17}]}]}
  + {:expr/operands nil}

Thanks for an excellent project.