Let's assume I wanted to downgrade to from MySQL 8 to MySQL 5.7. I know this isn't supported, but what kind of complications am I likely to encounter.

The docs say,

The only supported alternative is to restore a backup taken before upgrading. It is therefore imperative that you backup your data before starting the upgrade process.

Let's say I buck the caveat, and dump on 8 and revive on 5.7? What should I expect? Dumping on 5.x would product comments like

/*!40101 SET character_set_client = @saved_cs_client */;

These comments are documented as,

If you add a version number after the ! character, the syntax within the comment is executed only if the MySQL version is greater than or equal to the specified version number.

Are those kind of comments still produced by version 8? If so, what kind of scenarios would they not cover?

  • 1
    Did you run a v8 dump yourself? If so, are those kind of comments still produced?
    – mustaccio
    Feb 14, 2020 at 16:40
  • 1
    2 things i can think of: Unknown collation: 'utf8mb4_0900_ai_ci', and the passwords from your users..
    – Luuk
    Feb 14, 2020 at 17:09
  • Can you tell the applications make use of MySQL-8.0 features?
    – danblack
    Feb 19, 2020 at 23:27
  • 1
    I feel like this needs to be a self-answered question. As the person with the running MySQL 8 DB (presumably), can you JFDI on a newly provisioned 5.7 box and then post back the issues you saw? Feb 20, 2020 at 9:05
  • @PeterVandivier i'm not the person running it, i'm asking a pretty abstract question i figure someone has tried this. $work is building something that does this, and i'm doing preliminary research. Feb 21, 2020 at 16:36


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