Transaction Data

Transaction data is how data of a transaction is represented in Triplox. Triplox’s transaction data is closely modelled after Datomic’s transaction data. It purely concerns the transaction data constructs and not the semantics of a Triplox transaction. We will explain every concept via EDN syntax used by the Clojure client. The Java and Rust client also support the EDN syntax as strings, but they both also have explicit typed constructors for the transaction data. Every transaction data construct gets in the end translated to a Datom or a set of Datoms. The Datom is the most important concept to understand if you wish to understand transaction data. Transaction data is a vector of a assertions, retractions, assertions in map form (asserting multiple attributes about an entity) or an entity retraction.

Assertion / Retraction

The most basic form to assert a fact is via a standard assertion.

[:db/add entity-id attribute value]

The following example asserts that the entity id 123 (presumably a person) should have the name “Lovelace”.

[:db/add 123 :person/name "Lovelace"]

To remove data in Triplox, one retracts the EAV triple.

[:db/retract entity-id attribute value]

We currently expect a value for a retraction. A retraction without a value will fail. Transaction entity ids are not known at transaction time. These are assigned when the indexer has validated the transaction only then the transaction id is appended to the EAV permutations.

Map assertion form

Often when asserting facts about an entity we want to assert more than one fact. Asserting multiple facts about the same entity can be achieved via a map assertion. The map contains key/value pairs corresponding to attribute/value pairs.

For example asserting facts about a person could be achieved via

{:person/first-name "Ada"
 :person/last-name "Lovelace"
 :person/profession "Programmer"}

There key :db/id is special syntax sugar for identifying an entity via entity id. A map of the form

{:db/id 123
 :person/first-name "Ada"
 :person/last-name "Lovelace" }

is the same as the two transaction operations

[:db/add 123 :person/first-name "Ada"]
[:db/add 123 :person/last-name "Lovelace"]

Entity retraction

TODO

Tempids

Lookup refs

Idents