Demystifying Databases: Correctness Anomalies Under Serializable Isolation

https://fauna.com/blog/demystifying-database-systems-correctness-anomalies-under-serializable-isolation

by evanweaver • 7 years ago

71 16 7 years ago

gigatexal3• 7 years ago

This seems like a veiled salvo towards the folks at CockroachDB

ryanworl• 7 years ago

For those wondering, since CockroachDB is not mentioned by name here, the post [1] from the same author on his own site does explicitly mention CockroachDB.

"However, (unlike Google Spanner) CockroachDB does not wait for the maximum clock skew bound to pass before committing a transaction. Therefore, it is possible in CockroachDB for a transaction to commit, and a later transaction to come along (that writes data to a different partition), that was caused by the earlier one (that started after the earlier one finished), and still receive an earlier timestamp than the earlier transaction."

[1] https://dbmsmusings.blogspot.com/2019/06/correctness-anomali...

jasonwatkinspdx4• 7 years ago

This is a bit puzzling. It seems Abadi is unaware cockroachdb uses HLC, and does capture causality across partitions.

quizotic• 7 years ago

This is Dan Abadi we're talking about. More importantly, the points he makes are important, clear and true. If that causes heartburn for Vendor A and pride for Vendor B, that's secondary. The primary goal is to help users of distributed database systems understand the kind of trouble they can encounter with anything less than strict serializability.

NB: there are important applications where correctness in specific situations is not paramount. Double-click and ad-serving companies in general are more concerned about speed and throughput and are generally willing to have approximate correctness. Strict serializability isn't a universal value, but it's good to know about when you DO care about the kinds of anomalies Dan illustrates.

AtlasBarfed• 7 years ago

Fauna is a CP system, correct?

thekhatribharat2• 7 years ago

Ref: https://martin.kleppmann.com/2015/05/11/please-stop-calling-...

thekhatribharat2• 7 years ago

Shameless Plug (a summary of current NoSQL/NewSQL market and each's prominent features) - https://medium.com/open-factory/nosql-newsql-a-smorgasboard-...

Demystifying Databases: Correctness Anomalies Under Serializable Isolation

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