July 23, 2014

Why ALTER TABLE shows as two transactions in SHOW ENGINE INNODB STATUS

When executing an ALTER TABLE, InnoDB (and XtraDB) will create two InnoDB transactions: One transaction is created when the table being ALTERed is locked by the server. This will show up as something like “TABLE LOCK table schema.table_name trx id XXXX lock mode S” in SHOW ENGINE INNODB STATUS. Another is created when adding or […]

Building Indexes by Sorting In Innodb (AKA Fast Index Creation)

Innodb can indexes built by sort since Innodb Plugin for MySQL 5.1 which is a lot faster than building them through insertion, especially for tables much larger than memory and large uncorrelated indexes you might be looking at 10x difference or more. Yet for some reason Innodb team has chosen to use very small (just […]

Troubleshooting MySQL Memory Usage

One of the most painful troubleshooting tasks with MySQL is troubleshooting memory usage. The problem usually starts like this – you have configured MySQL to use reasonable global buffers, such as innodb_buffer_size, key_buffer_size etc, you have reasonable amount of connections but yet MySQL takes much more memory than you would expect, causing swapping or other […]

The relationship between Innodb Log checkpointing and dirty Buffer pool pages

This is a time-honored topic, and there’s no shortage of articles on the topic on this blog. I wanted to write a post trying to condense and clarify those posts, as it has taken me a while to really understand this relationship. Some basic facts Most of us know that writing into Innodb updates buffer […]

Benchmarks of new innodb_flush_neighbor_pages

In our recent release of Percona Server 5.5.19 we introduced new value for innodb_flush_neighbor_pages=cont. This way we are trying to deal with the problem of InnoDB flushing.

Optimizing InnoDB for creating 30,000 tables (and nothing else)

Once upon a time, it would have been considered madness to even attempt to create 30,000 tables in InnoDB. That time is now a memory. We have customers with a lot more tables than a mere 30,000. There have historically been no tests for anything near this many tables in the MySQL test suite. So, […]

Helgrinding MySQL with InnoDB for Synchronisation Errors, Fun and Profit

It is no secret that bugs related to multithreading–deadlocks, data races, starvations etc–have a big impact on application’s stability and are at the same time hard to find due to their nondeterministic nature.  Any tool that makes finding such bugs easier, preferably before anybody is aware of their existence, is very welcome.

InnoDB compression woes

InnoDB compression is getting some traction, and I see quite contradictory opinions. Someone has successful deployments in productions, and someone says that compression in current implementation is useless. To get some initial impression about performance I decided to run some sysbench with multi-tables benchmarks. I actually was preparing to do complex research, but even first […]

Flexviews is a working scalable database transactional memory example

http://Flexvie.ws fully implements a method for creating materialized views for MySQL data sets. The tool is for MySQL, but the methods are database agnostic. A materialized view is an analogue of software transactional memory. You can think of this as database transactional memory, or as database state distributed over time, but in an easy way […]

Innodb Caching (part 2)

Few weeks ago I wrote about Innodb Caching with main idea you might need more cache when you think you are because Innodb caches data in pages, not rows, and so the whole page needs to be in memory even if you need only one row from it. I have created the simple benchmark which […]