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Event Sourcing is a technical term, it's the idea that instead of mutating your database, you should instead have a log and insert a new log entry saying that y

Event Sourcing is a technical term, it's the idea that instead of mutating your database, you should instead have a log and insert a new log entry saying that you changed this value to that, etc. The idea is that this helps you do cool stuff like temporal queries (i.e. make a query "as the entire database looked like a month ago") or look at historical values and changes of things. This matters a lot in some fields. Of course then there's the matter of how to do this efficiently. You can build event sourcing on top of a regular RDBMS but if there is database-level support (as in PumpkinDB), then maybe some things are more efficient. Read more: https://martinfowler.com/eaaDev/EventSourcing.html https://martinfowler.com/eaaDev/EventSourcing.html

mattdeboard 10y ago
This sounds like my (probably wrong/incomplete) understanding of Datomic?
- grzm 10y ago
  I believe you could use Datomic for event sourcing, though it wasn't explicitly designed for the job and may not be the best choice depending on the requirements of your system as a whole. Bobby Calderwood at Capital One has a talk on a system which includes both event sourcing (using Kafka, IIRC) and Datomic: https://speakerdeck.com/bobbycalderwood/commander-better-distributed-applications-through-cqrs-event-sourcing-and-immutable-logs https://speakerdeck.com/bobbycalderwood/commander-better-dis...
  - mattdeboard 10y ago
    Nice, thank you.
gritzko 10y ago
Virtually every db works like that under the hood. They expose it differently, though. Kafka has nothing but log, for example.
- Groxx 10y ago
  e.g. https://dev.mysql.com/doc/refman/5.6/en/binary-log.html https://dev.mysql.com/doc/refman/5.6/en/binary-log.html
- solidsnack9000 10y ago
  They do but it's usually not exposed in a useful way. Postgres once had this feature... https://www.postgresql.org/docs/6.3/static/c0503.htm https://www.postgresql.org/docs/6.3/static/c0503.htm
  - anarazel 10y ago
    We actually expose something to support event sourcing: https://www.postgresql.org/docs/current/static/logicaldecoding.html https://www.postgresql.org/docs/current/static/logicaldecodi... - although that's very different from the old time travel feature. Edit: missing word

mattdeboard 10y ago

This sounds like my (probably wrong/incomplete) understanding of Datomic?

grzm 10y ago
I believe you could use Datomic for event sourcing, though it wasn't explicitly designed for the job and may not be the best choice depending on the requirements of your system as a whole. Bobby Calderwood at Capital One has a talk on a system which includes both event sourcing (using Kafka, IIRC) and Datomic: https://speakerdeck.com/bobbycalderwood/commander-better-distributed-applications-through-cqrs-event-sourcing-and-immutable-logs https://speakerdeck.com/bobbycalderwood/commander-better-dis...
- mattdeboard 10y ago
  Nice, thank you.

gritzko 10y ago

Virtually every db works like that under the hood. They expose it differently, though. Kafka has nothing but log, for example.

Groxx 10y ago
e.g. https://dev.mysql.com/doc/refman/5.6/en/binary-log.html https://dev.mysql.com/doc/refman/5.6/en/binary-log.html
solidsnack9000 10y ago
They do but it's usually not exposed in a useful way. Postgres once had this feature... https://www.postgresql.org/docs/6.3/static/c0503.htm https://www.postgresql.org/docs/6.3/static/c0503.htm
- anarazel 10y ago
  We actually expose something to support event sourcing: https://www.postgresql.org/docs/current/static/logicaldecoding.html https://www.postgresql.org/docs/current/static/logicaldecodi... - although that's very different from the old time travel feature. Edit: missing word