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Postgres supports multi-master replication, among other replication models. This could provide an interesting target. In a classic single node configuration,

Postgres supports multi-master replication, among other replication models. This could provide an interesting target. In a classic single node configuration, a confirmation that its transaction isolation behaviors exhibited the corresponding anomalies would be valuable. So I think there’s value in this ask.

samdk 6y ago
Postgres doesn't natively support multi-master. (Although there are a variety of open source/proprietary offerings that add support for it to various degrees.)
- deleted 6y ago
  [deleted]
takeda 6y ago
PostgreSQL doesn't offer multi master replication. There are extensions that do, but if aphyr will evaluate them he should emphasize that he is treating them not the PostgreSQL (unless he finds a bug in PostgreSQL itself). I think he did something similar for MySQL when evaluating the Galera cluster.
- politician 6y ago
  Jepsen reports often include two distinct types of analyses: correctness in a distributed storage system under a variety of failure scenarios, and in-depth analysis of consistency claims. Both examinations are extremely helpful. In a single write master configuration, Postgres runs transactions concurrently, so the consistency analysis is still quite relevant. I don’t think it’s a stretch to say that everyone expects Postgres to get top marks in this configuration and it would be worth confirming that this is the case.
  - takeda 6y ago
    Actually he already did analyze PostgreSQL: https://aphyr.com/posts/282-call-me-maybe-postgres https://aphyr.com/posts/282-call-me-maybe-postgres But it was long ago, and maybe needs to be redone? Edit: after re-reading it he treats it as a distributed system because client and server is over network. And that is true, it can also be thought of as a distributed system because as you said transactions are concurrent and are running as separate processes. Although in these cases you can't have a partition (which aphyr uses to find weaknesses), or maybe there is something equivalent that happens?
- zozbot234 6y ago
  > PostgreSQL doesn't offer multi master replication. Not in itself, but it does offer a PREPARE TRANSACTION - COMMIT PREPARED / ROLLBACK PREPARED extension that could be used to add such support in the future. This would not be unprecedented, as the simpler case of db sharding is already being supported via the PARTITION BY feature, combined with "FOREIGN" database access.

samdk 6y ago

Postgres doesn't natively support multi-master. (Although there are a variety of open source/proprietary offerings that add support for it to various degrees.)

deleted 6y ago
[deleted]

takeda 6y ago

PostgreSQL doesn't offer multi master replication. There are extensions that do, but if aphyr will evaluate them he should emphasize that he is treating them not the PostgreSQL (unless he finds a bug in PostgreSQL itself). I think he did something similar for MySQL when evaluating the Galera cluster.

politician 6y ago
Jepsen reports often include two distinct types of analyses: correctness in a distributed storage system under a variety of failure scenarios, and in-depth analysis of consistency claims. Both examinations are extremely helpful. In a single write master configuration, Postgres runs transactions concurrently, so the consistency analysis is still quite relevant. I don’t think it’s a stretch to say that everyone expects Postgres to get top marks in this configuration and it would be worth confirming that this is the case.
- takeda 6y ago
  Actually he already did analyze PostgreSQL: https://aphyr.com/posts/282-call-me-maybe-postgres https://aphyr.com/posts/282-call-me-maybe-postgres But it was long ago, and maybe needs to be redone? Edit: after re-reading it he treats it as a distributed system because client and server is over network. And that is true, it can also be thought of as a distributed system because as you said transactions are concurrent and are running as separate processes. Although in these cases you can't have a partition (which aphyr uses to find weaknesses), or maybe there is something equivalent that happens?
zozbot234 6y ago
> PostgreSQL doesn't offer multi master replication. Not in itself, but it does offer a PREPARE TRANSACTION - COMMIT PREPARED / ROLLBACK PREPARED extension that could be used to add such support in the future. This would not be unprecedented, as the simpler case of db sharding is already being supported via the PARTITION BY feature, combined with "FOREIGN" database access.