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Displaying posts with tag: autocommit (reset)
More on (transactional) MySQL metadata locks

Two years ago Ovais Tariq had explained in detail what kinds of problems existed before MySQL introduced metadata locks in 5.5.3 and how these locks help to prevent them. Still, some implications of metadata locking in MySQL remain unclear for users – DBAs and even software developers that target recent MySQL versions. I’ve decided to include a slide or two into the presentation about InnoDB locks and deadlocks I plan to make (with my colleague Nilnandan Joshi) on April 16 at Percona Live 2015.

I decided to do this as …

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Multi-master data conflicts - Part 1: understanding the problem

What is a conflict?

Readers of this blog know that one of my favorite tools, Tungsten Replicator, can easily create multi-master replication topologies, such as all-masters, star, fan-in. While this is good news for system designers and ambitious DBAs, it also brings some inconvenience. When you allow updates to happen in more than one master, you risk having conflicts. You may have heard this term before. For the sake of clarity, let's define what conflicts are, before analyzing each case in detail.

You have a conflict when several sources (masters) update concurrently the same data in asynchronous replication.

It's important to stress that this happens with asynchronous replication. In a truly synchronous cluster, where all data is kept consistent through 2-phase …

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Dispelling some unintentional MySQL FUD
There are three types of FUD: the first and more genuine is (#1) the intentional spreading of falsehood, mostly to gain some marketing advantage over a competing product. While I despise this practice, I understand it.
Then there is (#2) FUD spread by ignorance, when the originators are so blindly enraged by their hatred for a product that they don't care about getting the facts straight.
And finally, there is a third kind, not less dangerous, which is (#3) the spreading of FUD with good intentions, when the authors believe that they have the facts straight and they want to help.

I have recently come across two examples of unintentional FUD. For different reasons, my …

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Showing entries 1 to 3