Hello, my current host strongly suggest to use InnoDB vs. MyISAM for DB (considering it uses MariaDB which is probably the most popular MySQL now). It should increase overall performance over MyISAM.

So I wanted to check it - I know how to change it in PhpMyAdmin, BUT I read this article: https://mariadb.com/kb/en/library/converting-tables-from-myisam-to-innodb/ which makes valid points about Database INDEX issues / recommendations. So just changing the tables is not enough to do a proper upgrade.

My question is - would miniBB be affected by these Indexes? How to optimize them on InnoDB table to fully take advantage of InnoDB?

May be you need to start from this. Why did this recommendation came up and what for? Any issues discovered?

As far as I remember, InnoDB is good when there's a lot of insertions and new updates of records. For example, it would be good in banking, there are a lot of new transactions coming up each second, and not so much reading of DB. Instead, myISAM is good at reading, and forums are exactly about this. Your visitors read the forums much more than write messages.

The article seems to provide valid points for the upgrade. The most notable is a remark about FULLTEXT index missing in InnoDB. Some miniBB mods could be affected by this.

Also, if I remember properly, some tables in miniBB or its add-ons may not have a primary key. That could also be the issue.

But you actually need to start from the very first question in my post. InnoDB is just not the proper indexing system for forums, IMO. It won't bring any advantages in this case.

It came up when it turned out MySQL 5.6 is at 'end of life' - see: https://www.fromdual.com/support-for-mysql-from-oracle - then Cpanel / WHM recommends MariaDB 10.2 at this point, that's why I researched it..

Besides, it looks that myISAM is going to be depreciated too: https://www.percona.com/blog/2016/10/11/mysql-8-0-end-myisam/

I did a test - copied a DB and changed MyISAM to InnoDB on all tables. Then added a condition to read innoDB when accessing the site from my IP. From what I see, the site worked without any changes, even though I'm sure the Indexes are not optimized (I think innoDB automatically adds a Primary key or Index to the first NULL item, but it's probably not the fastest and most optimized way of doing it).

I wouldn't pay big attention to bloggers and unofficial news (specially 2-years old). On mysql.com I didn't find a note about myISAM being deprecated soon. I suppose it's too early to take such news seriously, because definitely there will be a lot of users which will be against ruining myISAM. Like the author of one of the comments in above article,

I'd rather agree to this. There are a lot of websites build on myISAM and their structure doesn't require anything more complicated which InnoDB provides. I'm mostly sure that if there will be no more lite and free mySQL community edition which supports myISAM, then this niche will be taken by some other product. Millions of small websites simply no not need difficult database. In this case Oracle risks to lose mySQL community as it happened with postgreSQL some time ago. PostgreSQL already was similarly bloated and see where it's now - almost forgotten.

Also let's not forget that mySQL is not just the only one tool we need for forums. The primary thing is PHP and all scripts actually rely on PHP-mySQL connectors. Whatever new is invented in mySQL it should be also supported in PHP, but now guess how many servers still support PHP 5.x because in PHP 7.x many functions were abandoned and that made older websites freezed? There are a lot of such servers. People just start dislike critical changes happening too often, preferring to stay with something stable.

So I doubt Oracle will abandon myISAM easily :) it will kill the primary goal of mySQL project. Then mostly everyone will just switch to another database.

And what about the search?

I suppose you would note some difference only if you'd have the amount if records counted by millions -5, 10, 20 millions... For the smaller database you should note the difference only in the size of DB i.e. how many space it takes on the disk.

Searching seems to work too. Yes - total DB size went from about 130MB to 220MB.

It's still a very small database :) InnoDB is more for websites like Facebook, instant chats with thousands if not millions of users online, heavy reading and writing... enterprise database editions, cloud servers. Without all that myISAM is more suitable for an average hardware server with a simple architecture, cheap projects, what miniBB is actually created for, too.

The size change was surprising - what it would need the extra 30% for, it is holding text one way or the other. I see possibly the best way is to upgrade to MariaDB which supports MyISAM in new versions too.

Indeed it could be the best decision at this period of time... Seems MariaDB is supported by most of hosters nowadays and at this stage it tends to replicate the "good old known" mySQL, thus with an official support myISAM in the future... As you may know, miniBB software doesn't need anything bloated, and InnoDB is definitely not the best choice for forums, that's why MariaDB should work like previously mySQL worked for years. At least, this is my personal recommendation so far.