You can watch the video of my linux.conf.au 2014 talk here: http://mirror.linux.org.au/linux.conf.au/2014/Wednesday/28-Past_Present_and_future_of_MySQL_and_variants_-_Stewart_Smith.mp4

But let’s talk about things in blog form rather than video form :)

Back in 1979, there was UNIREG. A text UI to records (rows) in a database (err, table). The reason I mention UNIREG is that it had FoRMs which as you may have guessed by my capitalization there is where the FRM file comes from.

In 1986, UNIREG came to UNIX. That’s right kids, the 80×24 VT100 interface to ISAM (Index Sequential Access Method – basically rows are written in insert order and indexes point to them) came to UNIX. There was no generic query language, just FoRMs and reports. In fact, to this day, that …

This post was initially going to be two sets of polls: “What is the maximum number of columns in MySQL?” and “What is the minimum maximum number of columns in MySQL?”. Before you read on, ponder those questions and come up with your own answers… and see if you’re right or can prove me wrong!

Back in 2009, I finished what seemed an epic task in the Drizzle code base: banishing the FRM file. Why? We felt it was not a good idea to keep arbitrary and obscure limitations from the 1980s alive in the 21st century and instead wanted a modular system where the storage engines themselves owned their own metadata. This was a radical departure from the MySQL philosophy, and one that has truly paid off in the Drizzle code base. However… for those using MySQL, Percona Server, MariaDB or any other of the MySQL branches/forks, you …

Drizzle originally inherited the FRM file from MySQL (which inherited it from UNIREG). The FRM file stores metadata about a table; what columns it has, what type those columns are, what indexes, any default values, comments etc are all stored in the FRM. In the days of MyISAM, this worked relatively well. The row data was stored in table.MYD, indexes on top of it in table.MYI and information about the format of the row was
in table.FRM. Since MyISAM itself wasn’t crash safe, it didn’t really matter if creating/deleting the FRM file along with the table was either.

As more sophisticated engines were introduced (e.g. InnoDB) that had their own data dictionary, there started to be more of a problem. There were now two places storing information about a table: the FRM file and the data dictionary specific to the engine. Even if the data dictionary of the storage engine was crash safe, the FRM file was not plugged into that, so you …