MySQL 4.1 to 5.1 large scale upgrade
Posted by: Jcink Cink
Date: March 21, 2011 08:00PM


I'm looking for some general advice about an upgrade from MySQL 4.1 to MySQL 5.1. I have already the FAQ page which says "If you perform a binary upgrade without dumping and reloading tables, you cannot upgrade directly from MySQL 4.1 to 5.1 or higher."

With that said here is the environment, a multi-forum host with lots of tables in the database (1.5 to 2 million). Dumping and reloading would be really nasty for us.

However, I don't really know if it's necessary.

> Our tables are all MyISAM
> Our collations are all latin1_swedish_ci
> No InnoDB tables; skipped them in the config

Under the "Changes that cause index rebuilding to be necessary" on the FAQ page, none of what's written there applies to us.

I set up a test environment with one of our backups and tried just dropping everything in. The /mysql/ folder didn't like it, so I just erased it and let it recreate a new one. No problem.

Added new accounts, and then loaded up some test forums. I couldn't find a single thing that wasn't working. I made posts, went into places where I knew some queries were complicated and didn't find any issues at all. Search worked, deleting worked, etc. Debug output showed that things were pretty much the same in regard to MySQL reading from the existing indexes and I couldn't find any performance problems.

Yet CHECK TABLE still reports that "Table upgrade required."

Given all of the information above, is it *really* required? I feel like it's just displaying that message because it sees a version mismatch and that I could probably get away with this upgrade otherwise. A more painless way to bring the tables up to date for added performance reasons, etc, would be for me to do a background process to start checking them based on which ones are most active rather than going for them all.

For what it's worth: when I run REPAIR TABLE on any of the affected ones, it goes just fine. The table then reads OK during another CHECK TABLE.

If anyone has ever done anything like this before or can shed some light about what they think, it would be greatly appreciated.

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MySQL 4.1 to 5.1 large scale upgrade
March 21, 2011 08:00PM

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