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All the Perl that's Practical to Extract and Report

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  • I was reading a document comparing differences between PostgreSQL and MySQL []. It mentioned the different interpretations of transaction isolation and how some of the MySQL modes are inconsistent and weird.

    When comparing the two models, PostgreSQL enforces client separation where the data operated on is always consistent under all circumstances; as the MVCC documentation states, "the reason that PostgreSQL only provides two isolation levels is that this is the only sensible way to map the standard isolation levels to the multiversion concurrency control architecture." MySQL allows configurations where client code that doesn't commit transactions properly can result in a data view that would be considered inconsistent by PostgreSQL's stricter standards. However, in situations where it's acceptable for data being read to have small inconsistencies, being able to use a less strict locking could be a performance advantage for MySQL.
    It also some good links to understanding transaction logic.