biff.datalevin.adapter — io.github.datalevin/biff-datalevin 0.3.19

Biff 2 database adapter for Datalevin.

Provides a biff.core module that:

• starts a Datalevin connection
• implements biff.core's key-value store interface (:biff.core/kv-get, :biff.core/kv-set, :biff.core/kv-list)
• provides :biff.core/wrap-db-snapshot for consistent reads
• calls :biff.core/on-tx after transactions
• generates biff.graph resolvers from a Datalevin schema
• provides biff.fx handlers for queries and transactions

Example:

(def modules [(biff.fx/module) (biff.graph/module) (biff.datalevin.adapter/module {:biff.datalevin/db-path "data/myapp" :biff.datalevin/schema my-schema})])

(def start-order [:biff.datalevin/module])

See https://github.com/jacobobryant/biff/blob/master/docs/db-adapters.md

execute-tx clj

(execute-tx ctx tx-data)

Executes a Datalevin transaction, returning the transaction report.

Supports the special values :db/now and :db/uuid. :biff.core/on-tx is called after the transaction (via a connection listener).

fx-handlers clj

A biff.fx handlers map. Contains :biff.datalevin.fx/q and :biff.datalevin.fx/execute-tx.

kv-get clj

(kv-get ctx namespace* key*)

Implementation of :biff.core/kv-get.

Returns the value for key* in namespace*, or nil if unset.

kv-list clj

(kv-list ctx namespace*)

(kv-list ctx namespace* key-prefix)

Implementation of :biff.core/kv-list.

Returns a sorted vector of keys in namespace*. If key-prefix is set, only keys beginning with it are returned.

kv-schema clj

Datalevin schema for the biff.core key-value store.

kv-set clj

(kv-set ctx namespace* key* value)

Implementation of :biff.core/kv-set.

Sets key* in namespace* to value. A nil value deletes the key. Values are serialized with pr-str, so they must be readable by clojure.edn/read-string.

make-resolvers clj

(make-resolvers schema)

Returns a sequence of biff.graph resolvers, one for each entity type in schema (a Datalevin schema map).

Entity types are determined by attribute namespaces, e.g. all :user/* attrs belong to the :user entity type. The primary key is :<ns>/id if it exists, otherwise the first unique attribute in the namespace.

Ref attributes are returned as joins. The target entity type is inferred from the attribute name: :session/user refers to :user/id and :user/pet-id refers to :pet/id. For refs whose names don't imply their target (e.g. :group/members), set :biff.datalevin/ref in the schema entry:

:group/members {:db/valueType :db.type/ref :db/cardinality :db.cardinality/many :biff.datalevin/ref :user/id}

If a ref attribute ends in -id, that attribute is also returned as a scalar containing the referenced primary key value.

module clj

(module {:biff.datalevin/keys [db-path schema opts snapshot?]})

Returns a biff.core module for Datalevin. Module ID is :biff.datalevin/module.

Options: :biff.datalevin/db-path - Path to the Datalevin database directory (required) :biff.datalevin/schema - Datalevin schema map :biff.datalevin/opts - Additional options passed to d/get-conn :biff.datalevin/snapshot? - Set to false to skip :biff.core/wrap-db-snapshot (default true)

Other modules may contribute schema by including a :biff.datalevin/schema key in their module map.

On start, opens a connection and adds to the system map:

:biff.datalevin/conn - The Datalevin connection :biff.core/kv-get - biff.core key-value store :biff.core/kv-set :biff.core/kv-list :biff.core/wrap-db-snapshot - Provides consistent reads (unless :biff.datalevin/snapshot? is false)

q clj

(q ctx query & args)

Queries the Datalevin database.

ctx is a system map containing :biff.datalevin/conn (or a Datalevin connection or database value).

Example: (q ctx '[:find ?e :where [?e :user/email "[e-mail]"]])

submit-tx clj

(submit-tx ctx tx-data)

Alias for execute-tx.