New MariaDB/MySQL storage engines such as MyRocks and TokuDB have renewed interest in using engines other than InnoDB. This is great, but also presents new challenges. In this article, I will describe work that I am currently finishing, and which addresses one such challenge.

For example, the left bar in the figure shows what happens to MyRocks replication performance when used with a default install where the replication state table uses InnoDB. The middle bar shows the performance improvement from my patch.

Current MariaDB and MySQL replication uses tables to transactionally record the replication state (eg mysql.gtid_slave_pos). When non-InnoDB storage engines are introduced the question becomes: What engine should be used for the replication table? Any choice will penalise other engines heavily by injecting a cross-engine transaction with every replicated change. Unless all tables can be migrated to the …

As promised, here is the follow up of the MySQL 8.0-dev Progress teaser ;-)
so, yes, we expect to see the most hot contentions gone, as it's seen from the following graph : Observations :

• the graph is representing the spin waits / spin rounds events happening during the same Sysbench Update-NoKEY workload
• the load is progressing from 8 concurrent users to 16, 32, .. 512
• 3 engines are tested one after one : MySQL 5.7, MySQL 8.0 (current DMR), MySQL 8.0-dev (current prototype)
• first all 3 engines are running on 22cores-HT only (1 CPU socket)
• then, the second time : on 44cores-HT (2 CPU sockets)
• and the most important thing to retain about this graph is that on 8.0-dev we see all main hot contentions gone ;-)

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MySQL 8.0.1 introduces new features and improvements to replication. The next sections summarize some related to performance.

1. WL#9556 – Writeset-based dependency tracking on the master

Transaction writesets can now be used to evaluate which transactions are independent and can be executed in parallel on the binary log applier on the asynchronous slaves.…

Query Reviews part 2: pt-query-digest

One task that can really help reduce future problems is to do a periodic query review. I’ve been using pt-query-digest to do this since 2010 (back when it was part of Ma’atkit, mk-query-digest!), and while I have presented the idea several times at conferences, I have never blogged about it.

I am going to share a secret with you – I blog not just to share information with YOU, but to share information with ME. Future me. This comes up because I am working on a query review at Salesforce.com for one of our busiest shards. I went to go look up a blog post on using pt-query-digest, because it’s a handy cheat sheet….and….I never did it. So, here goes!

This is the first blog post in what will …

Starting on MySQL 8.0.1, a very updated replica server will be more efficient (and probably faster) than previous MySQL versions because of improvements in the relationship between the replication threads. Preliminary testing showed a benefit of up to 65% on Sysbench Update Index.…

MySQL 8.0.1 introduces a new mechanism to track the dependencies between transactions. This feature is used to optimize the binary log applier on asynchronous replication slaves, improving the throughput significantly on workloads where there is low-concurrency on the master and/or on systems with very fast storage.…

In this blog, we’ll look at how to achieve better-than-linear scaling.

Scalability is the capability of a system, network or process to handle a growing amount of work, or its potential to be enlarged to accommodate that growth. For example, we consider a system scalable if it is capable of increasing its total output under an increased load when resources (typically hardware) are added: https://en.wikipedia.org/wiki/Scalability.

It is often accepted as a fact that systems (in particular databases) can’t scale better than linearly. By this I mean when you double resources, the expected performance doubles, at best (and often is less than doubled).  

We can attribute this assumption to Amdahl’s law (https://en.wikipedia.org/wiki/Amdahl%27s_law), and later …

In this blog post, we’ll look at the actions and efforts Percona experts took to scale Percona XtraDB Cluster.

Introduction

When we first started analyzing Percona XtraDB Cluster performance, it was pretty bad. We would see contention even with 16 threads. Performance was even worse with sync binlog=1, although the same pattern was observed even with the binary log disabled. The effect was not only limited to OLTP workloads, as even other workloads (like update-key/non-key) were also affected in a wider sense than OLTP.

That’s when we started analyzing the contention issues and found multiple problems. We will discuss all these problems and the solutions we adapted. But …

MySQL 8.0 introduces Common Table Expressions (CTE). My colleague Guilhem has written several blog posts on how to use CTEs , and you can also read about it in the MySQL 8.0 Reference Manual. In this blog post, I will focus on how using a CTE instead of a view or a derived table can improve performance.…

One of the interesting features introduced in MySQL 5.7 is that innodb_buffer_pool_size is a dynamic variable (since 5.7.5, to be more specific). Yet, past experience tells us that just because a variable is dynamic, it does not make it is safe to change it on the fly.

To find out how safe this new feature is, I measured throughput on a synthetic workload (sysbench 1.0 running the oltp script) as I made changes to this variable. In this post, I will show the results that came through.

The Environment

For my tests, I used a Google Cloud Compute instance of type n1-standard-4 (that is 4 vCPUs and 15 GB of memory) with 25 GB of persistent …