[Bug]: schema updates and removals are not consistent

[kordano]

What version of Datahike are you using?

0.5.1501

What version of Java are you using?

openjdk version "11.0.15" 2022-04-19

What operating system are you using?

Ubuntu 20.04.4 LTS

What database EDN configuration are you using?

{:store {:backend :mem
             :id "schema_test"}
 :keep-history?      true
 :schema-flexibility :write
 :attribute-refs?    true}

Describe the bug

There are inconsistencies when updating or removing the schema.

What is the expected behaviour?

Datahike should have a clear strategy and documentation on schema updates.

How can the behaviour be reproduced?

(require '[datahike.api :as d])
(def schema [{:db/cardinality :db.cardinality/one
              :db/ident       :name
              :db/index       true
              :db/unique      :db.unique/identity
              :db/valueType   :db.type/string}
             {:db/ident       :parents
              :db/cardinality :db.cardinality/many
              :db/valueType   :db.type/ref}
             {:db/ident       :age
              :db/cardinality :db.cardinality/one
              :db/valueType   :db.type/long}])

(def cfg {:store              {:backend :mem
                               :id "schema_upgrade"}
          :keep-history?      true
          :schema-flexibility :write
          :attribute-refs?    true})

(do
  (d/delete-database cfg)
  (d/create-database cfg))

(def conn (d/connect cfg))

(d/transact conn {:tx-data schema})

(d/schema @conn)

(d/datoms @conn :eavt)

(d/transact conn [{:name "Alice"
                   :age  25}
                  {:name "Bob"
                   :age  35}])


(d/transact conn [{:name    "Charlie"
                   :age     5
                   :parents [[:name "Alice"] [:name "Bob"]]}])

(d/q '[:find ?e ?n
       :where
       [?e :name ?n]] @conn)
;;=> #{[44 "Charlie"] [43 "Bob"] [42 "Alice"]}

(d/transact conn {:tx-data [[:db/retractEntity [:db/ident :name]]]})
;; => this shouldn't be possible when there is still data with that attribute!

(d/q '[:find ?e ?n
       :where
       [?e :name ?n]] @conn)
;;=> #{[17 :db.type/boolean]
  ;; [8 11]
  ;; [8 :db.install/attribute]
  ;; [40 :parents]
  ;; [20 :db.type/float]
  ;; [1 33]
  ;; [9 :db/txInstant]
  ;; [7 11]
  ;; [44 43]
  ;; [2 "An attribute's value type"]
  ;; [40 25]
  ;; [3 19]
  ;; [5 "An attribute's index selection"]
  ;; [1 23]
  ;; [4 26]
  ;; [19 :db.type/cardinality]
  ;; [30 :db.type/valueType]
  ;; [6 28]
  ;; [4 :db/doc]
  ;; [3 :db/cardinality]
  ;; [40 10]
  ;; [42 25]
  ;; [6 "An attribute's unique selection"]
  ;; [33 :db.unique/value]
  ;; [36 :db/tupleTypes]
  ;; [41 24]
  ;; [536870913 #inst "2022-05-06T13:06:54.787-00:00"]
  ;; [29 :db.type/uuid]
  ;; [14 :db.part/user]
  ;; [7 "An attribute's history selection"]
  ;; [9 "A transaction's time-point"]
  ;; [2 :db/valueType]
  ;; [32 :db.unique/identity]
  ;; [2 30]
  ;; [9 true]
  ;; [9 22]
  ;; [536870914 #inst "2022-05-06T13:06:57.597-00:00"]
  ;; [8 "Only for interoperability with Datomic"]
  ;; [24 :db.type/long]
  ;; [34 :db/isComponent]
  ;; [21 :db.type/number]
  ;; [13 :db.part/tx]
  ;; [38 :db.type/tuple]
  ;; [4 11]
  ;; [536870916 #inst "2022-05-06T13:07:01.761-00:00"]
  ;; [1 11]
  ;; [44 "Charlie"]
  ;; [1 :db/ident]
  ;; [27 :db.type/symbol]
  ;; [16 :db.type/bigint]
  ;; ...}

[jsmassa]

A solution should also consider imports and exports

[jsmassa]

Issue #13 also deals with schema changes