Datomic_zero - What is in an empty Datomic database (and how to find out)?

datomic_zero.clj

(ns datomic-zero
  (:use [datomic.api :only [q db entity] :as d])
  (:use (clojure pprint)))

;; URI as identifyer of the db
(def uri "datomic:mem://trials")

;; create database
(d/create-database uri)

;; connect to database
(def conn (d/connect uri))

;; type: datomic.db.Db
;; get a snapshot of empty DB
(def db-zero (db conn))

;; this asks for all entity having an ident.
;; (there may be others, I just don't know how to find them.)
(def orig-entities (sort-by first
                            (seq (q '[:find ?c ?i :where [?c :db/ident ?i ]] db-zero))))

(pprint orig-entities)

;; Prints as follows:
([0 :db.part/db]
 [1 :db/add]
 [2 :db/retract]
 [3 :db.part/tx]
 [4 :db.part/user]
 [10 :db/ident]
 [11 :db.install/partition]
 [12 :db.install/valueType]
 [13 :db.install/attribute]
 [14 :db.install/function]
 [20 :db.type/ref]
 [21 :db.type/keyword]
 [22 :db.type/long]
 [23 :db.type/string]
 [24 :db.type/boolean]
 [25 :db.type/instant]
 [26 :db.type/fn]
 [27 :db.type/bytes]
 [35 :db.cardinality/one]
 [36 :db.cardinality/many]
 [37 :db.unique/value]
 [38 :db.unique/identity]
 [39 :fressian/tag]
 [40 :db/valueType]
 [41 :db/cardinality]
 [42 :db/unique]
 [43 :db/isComponent]
 [44 :db/index]
 [45 :db/noHistory]
 [46 :db/lang]
 [47 :db/code]
 [48 :db.lang/clojure]
 [49 :db.lang/java]
 [50 :db/txInstant]
 [51 :db/fulltext]
 [52 :db/fn]
 [53 :db.fn/retractEntity]
 [54 :db.fn/cas]
 [55 :db.type/uuid]
 [56 :db.type/double]
 [57 :db.type/float]
 [58 :db.type/uri]
 [59 :db.type/bigint]
 [60 :db.type/bigdec]
 [61 :db/doc])



;; I now want to know the attributes too.
(def overview0 (map (fn [[i key]] (let [e (d/entity db-zero i)]
                                    (conj [i key]
                                          (map #(vector % (% e)) (keys e)))))

                    orig-entities))

(pprint overview0)

;; prints as

([0
  :db.part/db
  ([:db/doc
    "Name of the system partition. The system partition includes the core of datomic, as well as user schemas: type definitions, attribute definitions, partition definitions, and data function definitions."]
   [:db.install/function #{:db.fn/cas :db.fn/retractEntity}]
   [:db.install/attribute
    #{:db/noHistory :db.install/partition :db/cardinality
      :db.install/attribute :db/index :db/unique :db/fulltext
      :db/txInstant :db/lang :db/doc :db.install/valueType :db/code
      :db/isComponent :db/fn :db.install/function :db/valueType
      :db/ident :fressian/tag}]
   [:db.install/valueType
    #{:db.type/uuid :db.type/bigint :db.type/uri :db.type/ref
      :db.type/keyword :db.type/bytes :db.type/string :db.type/instant
      :db.type/fn :db.type/long :db.type/bigdec :db.type/boolean
      :db.type/double :db.type/float}]
   [:db.install/partition #{:db.part/db}]
   [:db/ident :db.part/db])]
 [1
  :db/add
  ([:db/doc
    "Primitive assertion. All transactions eventually reduce to a collection of primitive assertions and retractions of facts, e.g. [:db/add fred :age 42]."]
   [:db/ident :db/add])]
 [2
  :db/retract
  ([:db/doc
    "Primitive retraction. All transactions eventually reduce to a collection of assertions and retractions of facts, e.g. [:db/retract fred :age 42]."]
   [:db/ident :db/retract])]
 [3
  :db.part/tx
  ([:db/doc
    "Partition used to store data about transactions. Transaction data always includes a :db/txInstant which is the transaction's timestamp, and can be extended to store other information at transaction granularity."]
   [:db/ident :db.part/tx])]
 [4
  :db.part/user
  ([:db/doc
    "Name of the user partition. The user partition is analogous to the default namespace in a programming language, and should be used as a temporary home for data during interactive development."]
   [:db/ident :db.part/user])]
 [10
  :db/ident
  ([:db/doc "Attribute used to uniquely name an entity."]
   [:db/unique :db.unique/identity]
   [:db/cardinality :db.cardinality/one]
   [:db/valueType :db.type/keyword]
   [:db/ident :db/ident])]
 [11
  :db.install/partition
  ([:db/doc
    "System attribute with type :db.type/ref. Asserting this attribute on :db.part/db with value v will install v as a partition."]
   [:db/cardinality :db.cardinality/many]
   [:db/valueType :db.type/ref]
   [:db/ident :db.install/partition])]
 [12
  :db.install/valueType
  ([:db/doc
    "System attribute with type :db.type/ref. Asserting this attribute on :db.part/db with value v will install v as a value type."]
   [:db/cardinality :db.cardinality/many]
   [:db/valueType :db.type/ref]
   [:db/ident :db.install/valueType])]
 [13
  :db.install/attribute
  ([:db/doc
    "System attribute with type :db.type/ref. Asserting this attribute on :db.part/db with value v will install v as an attribute."]
   [:db/cardinality :db.cardinality/many]
   [:db/valueType :db.type/ref]
   [:db/ident :db.install/attribute])]
 [14
  :db.install/function
  ([:db/doc
    "System attribute with type :db.type/ref. Asserting this attribute on :db.part/db with value v will install v as a data function."]
   [:db/cardinality :db.cardinality/many]
   [:db/valueType :db.type/ref]
   [:db/ident :db.install/function])]
 [20
  :db.type/ref
  ([:db/doc
    "Value type for references. All references from one entity to another are through attributes with this value type."]
   [:fressian/tag :ref]
   [:db/ident :db.type/ref])]
 [21
  :db.type/keyword
  ([:db/doc
    "Value type for keywords. Keywords are used as names, and are interned for efficiency. Keywords map to the native interned-name type in languages that support them."]
   [:fressian/tag :key]
   [:db/ident :db.type/keyword])]
 [22
  :db.type/long
  ([:db/doc
    "Fixed integer value type. Same semantics as a Java long: 64 bits wide, two's complement binary representation."]
   [:fressian/tag :int]
   [:db/ident :db.type/long])]
 [23
  :db.type/string
  ([:db/doc "Value type for strings."]
   [:fressian/tag :string]
   [:db/ident :db.type/string])]
 [24
  :db.type/boolean
  ([:db/doc "Boolean value type."]
   [:fressian/tag :bool]
   [:db/ident :db.type/boolean])]
 [25
  :db.type/instant
  ([:db/doc
    "Value type for instants in time. Stored internally as a number of milliseconds since midnight, January 1, 1970 UTC. Representation type will vary depending on the language you are using."]
   [:fressian/tag :inst]
   [:db/ident :db.type/instant])]
 [26
  :db.type/fn
  ([:db/doc
    "Value type for database functions. See Javadoc for Peer.function."]
   [:fressian/tag :datomic/fn]
   [:db/ident :db.type/fn])]
 [27
  :db.type/bytes
  ([:db/doc
    "Value type for small binaries. Maps to byte array on the JVM."]
   [:fressian/tag :bytes]
   [:db/ident :db.type/bytes])]
 [35
  :db.cardinality/one
  ([:db/doc
    "One of two legal values for the :db/cardinality attribute. Specify :db.cardinality/one for single-valued attributes, and :db.cardinality/many for many-valued attributes."]
   [:db/ident :db.cardinality/one])]
 [36
  :db.cardinality/many
  ([:db/doc
    "One of two legal values for the :db/cardinality attribute. Specify :db.cardinality/one for single-valued attributes, and :db.cardinality/many for many-valued attributes."]
   [:db/ident :db.cardinality/many])]
 [37
  :db.unique/value
  ([:db/doc
    "Specifies that an attribute's value is unique. Attempts to create a new entity with a colliding value for a :db.unique/value will fail."]
   [:db/ident :db.unique/value])]
 [38
  :db.unique/identity
  ([:db/doc
    "Specifies that an attribute's value is unique. Attempts to create a new entity with a colliding value for a :db.unique/value will become upserts."]
   [:db/ident :db.unique/identity])]
 [39
  :fressian/tag
  ([:db/doc
    "Keyword-valued attribute of a value type that specifies the underlying fressian type used for serialization."]
   [:db/index true]
   [:db/cardinality :db.cardinality/one]
   [:db/valueType :db.type/keyword]
   [:db/ident :fressian/tag])]
 [40
  :db/valueType
  ([:db/doc
    "Property of an attribute that specifies the attribute's value type. Built-in value types include, :db.type/keyword, :db.type/string, :db.type/ref, :db.type/instant, :db.type/long, :db.type/bigdec, :db.type/boolean, :db.type/float, :db.type/uuid, :db.type/double, :db.type/bigint,  :db.type/uri."]
   [:db/cardinality :db.cardinality/one]
   [:db/valueType :db.type/ref]
   [:db/ident :db/valueType])]
 [41
  :db/cardinality
  ([:db/doc
    "Property of an attribute. Two possible values: :db.cardinality/one for single-valued attributes, and :db.cardinality/many for many-valued attributes. Defaults to :db.cardinality/one."]
   [:db/cardinality :db.cardinality/one]
   [:db/valueType :db.type/ref]
   [:db/ident :db/cardinality])]
 [42
  :db/unique
  ([:db/doc
    "Property of an attribute. If value is :db.unique/value, then attribute value is unique to each entity. Attempts to insert a duplicate value for a temporary entity id will fail. If value is :db.unique/identity, then attribute value is unique, and upsert is enabled. Attempting to insert a duplicate value for a temporary entity id will cause all attributes associated with that temporary id to be merged with the entity already in the database. Defaults to nil."]
   [:db/cardinality :db.cardinality/one]
   [:db/valueType :db.type/ref]
   [:db/ident :db/unique])]
 [43
  :db/isComponent
  ([:db/doc
    "Property of attribute whose vtype is :db.type/ref. If true, then the attribute is a component of the entity referencing it. When you query for an entire entity, components are fetched automatically. Defaults to nil."]
   [:db/cardinality :db.cardinality/one]
   [:db/valueType :db.type/boolean]
   [:db/ident :db/isComponent])]
 [44
  :db/index
  ([:db/doc
    "Property of an attribute. If true, create an AVET index for the attribute. Defaults to false."]
   [:db/cardinality :db.cardinality/one]
   [:db/valueType :db.type/boolean]
   [:db/ident :db/index])]
 [45
  :db/noHistory
  ([:db/doc
    "Property of an attribute. If true, past values of the attribute are not retained. Defaults to false."]
   [:db/cardinality :db.cardinality/one]
   [:db/valueType :db.type/boolean]
   [:db/ident :db/noHistory])]
 [46
  :db/lang
  ([:db/doc
    "Attribute of a data function. Value is a keyword naming the implementation language of the function. Legal values are :db.lang/java and :db.lang/clojure"]
   [:db/cardinality :db.cardinality/one]
   [:db/valueType :db.type/ref]
   [:db/ident :db/lang])]
 [47
  :db/code
  ([:db/doc
    "String-valued attribute of a data function that contains the function's source code."]
   [:db/fulltext true]
   [:db/cardinality :db.cardinality/one]
   [:db/valueType :db.type/string]
   [:db/ident :db/code])]
 [48
  :db.lang/clojure
  ([:db/doc
    "Value of :db/lang attribute, specifying that a data function is implemented in Clojure."]
   [:db/ident :db.lang/clojure])]
 [49
  :db.lang/java
  ([:db/doc
    "Value of :db/lang attribute, specifying that a data function is implemented in Java."]
   [:db/ident :db.lang/java])]
 [50
  :db/txInstant
  ([:db/doc
    "Attribute whose value is a :db.type/instant. A :db/txInstant is recorded automatically with every transaction."]
   [:db/index true]
   [:db/cardinality :db.cardinality/one]
   [:db/valueType :db.type/instant]
   [:db/ident :db/txInstant])]
 [51
  :db/fulltext
  ([:db/doc
    "Property of an attribute. If true, create a fulltext search index for the attribute. Defaults to false."]
   [:db/cardinality :db.cardinality/one]
   [:db/valueType :db.type/boolean]
   [:db/ident :db/fulltext])]
 [52
  :db/fn
  ([:db/doc
    "A function-valued attribute for direct use by transactions and queries."]
   [:db/cardinality :db.cardinality/one]
   [:db/valueType :db.type/fn]
   [:db/ident :db/fn])]
 [53
  :db.fn/retractEntity
  ([:db/doc
    "Retract all facts about an entity, including references from other entities and component attributes recursively."]
   [:db/code
    "(clojure.core/fn [db e] (datomic.builtins/build-retract-args db e))"]
   [:db/lang :db.lang/clojure]
   [:db/ident :db.fn/retractEntity])]
 [54
  :db.fn/cas
  ([:db/doc "Compare and swap the value of an entity's attribute."]
   [:db/code
    "(clojure.core/fn [db e a ov nv] (datomic.builtins/compare-and-swap db e a ov nv))"]
   [:db/lang :db.lang/clojure]
   [:db/ident :db.fn/cas])]
 [55
  :db.type/uuid
  ([:db/doc "Value type for UUIDs. Maps to java.util.UUID on the JVM."]
   [:fressian/tag :uuid]
   [:db/ident :db.type/uuid])]
 [56
  :db.type/double
  ([:db/doc
    "Floating point value type. Same semantics as a Java double: double-precision 64-bit IEEE 754 floating point."]
   [:fressian/tag :double]
   [:db/ident :db.type/double])]
 [57
  :db.type/float
  ([:db/doc
    "Floating point value type. Same semantics as a Java float: single-precision 32-bit IEEE 754 floating point."]
   [:fressian/tag :float]
   [:db/ident :db.type/float])]
 [58
  :db.type/uri
  ([:db/doc "Value type for URIs. Maps to java.net.URI on the JVM."]
   [:fressian/tag :uri]
   [:db/ident :db.type/uri])]
 [59
  :db.type/bigint
  ([:db/doc
    "Value type for arbitrary precision integers. Maps to java.math.BigInteger on the JVM."]
   [:fressian/tag :bigint]
   [:db/ident :db.type/bigint])]
 [60
  :db.type/bigdec
  ([:db/doc
    "Value type for arbitrary precision floating point numbers. Maps to java.math.BigDecimal on the JVM."]
   [:fressian/tag :bigdec]
   [:db/ident :db.type/bigdec])]
 [61
  :db/doc
  ([:db/doc "Documentation string for an entity."]
   [:db/fulltext true]
   [:db/cardinality :db.cardinality/one]
   [:db/valueType :db.type/string]
   [:db/ident :db/doc])])


;;-------------------
;; If we want to search for entities without a certain attribute
(defn attribute-not-set? [db id attr]
  (nil? (attr (d/entity db id))))

; without ident, but with doc (I did not find some ..)
(def no-ident (seq (q '[:find ?e
                        :where
                        [?e :db/doc]
                        [(DatomicTrials.core/attribute-not-set? $ ?e :db/ident)]]
                      (db conn))))