Question

Twitter has open sourced their Mysql source code.

This blog post http://engineering.twitter.com/2012/04/mysql-at-twitter.html mentions the different changes.

I have used Mysql as developer executing queries but never had to dig deep into its source code. I tried going through the source code on github https://github.com/twitter/mysql but was overwhelmed.
So thought I would post here and get some help.

1. I would like to better understand how Twitter’s changes has improved
   Mysql over the Oracle’s version.

2. If I were to make an apples to apples comaparison between Oracle’s version and Twitter’s version what are specific advantages disadvantages between the two.

There are many more questions that popped into my head.

I get that this is sort of an advanced DB topic, but I would love learn about it.

Answer 1

They describe the changes as including:

Add additional status variables, particularly from the internals of
InnoDB. This allows us to monitor our systems more effectively and
understand their behavior better when handling production workloads.

Optimize memory allocation on large NUMA systems: Allocate InnoDB’s
buffer pool fully on startup, fail fast if memory is not available,
ensure performance over time even when server is under memory
pressure.

Reduce unnecessary work through improved server-side
statement timeout support. This allows the server to proactively
cancel queries that run longer than a millisecond-granularity timeout.

Export and restore InnoDB buffer pool in using a safe and lightweight
method. This enables us to build tools to support rolling restarts of
our services with minimal pain.

Optimize MySQL for SSD-based machines,
including page-flushing behavior and reduction in writes to disk to
improve lifespan.

These are things that are important for a Twitter-scale web site. If you are building something that has to scale to that size – yes, those changes would be helpful. But, if you are building something more like every other mildly-popular web site in the world, you probably don’t need to be concerned with their changes. Most large web sites that run MySQL run it straight from the distribution.