Transactions#

Transactions accept the familiar entity-map and operation-vector data forms.

[{:db/id -1
  :person/name "Ada"
  :person/email "ada@example.com"}
 [:db/add -1 :person/active true]]

Supported operations include:

[:db/add entity attribute value]
[:db/retract entity attribute value]
[:db/retract entity attribute]
[:db/retractEntity entity]
[:db.fn/retractAttribute entity attribute]
[:db.fn/cas entity attribute old-value new-value]

Map transactions support tempids, lookup refs, nested component maps, reverse attributes, upserts, and cardinality-many values.

Reports#

A successful transaction returns:

• the database value before the transaction
• the database value after the transaction
• committed datoms
• resolved tempids
• the transaction ID

Every transaction has a :db/txInstant fact. Metadata added to :db/current-tx is stored on the same transaction entity.

[{:db/id :db/current-tx
  :audit/user 42}
 {:db/id 1
  :person/name "Ada"}]

Failed transactions do not change the connection or notify listeners.

Hypothetical transactions#

db-with returns a new database value without changing its source:

(def source (d/db conn))
(def changed
  (d/db-with source
    [[:db/add 1 :person/name "Ada"]]))

source and conn are unchanged.

Transaction functions#

The native API can register process-local callbacks that return transaction data. These callbacks are embedding hooks, not Datomic stored functions. VevDB does not persist host code.

See History for transaction time and log APIs.