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Displaying posts with tag: READ COMMITTED (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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MySQL performance implications of InnoDB isolation modes

Over the past few months I’ve written a couple of posts about dangerous debt of InnoDB Transactional History and about the fact MVCC can be the cause of severe MySQL performance issues. In this post I will cover a related topic – InnoDB Transaction Isolation Modes, their relationship with MVCC (multi-version concurrency control) and how they impact MySQL performance.

The MySQL Manual provides a decent description of transaction isolation modes supported by MySQL – I will not repeat it here but rather focus on performance implications.

SERIALIZABLE – This is the strongest …

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Runaway history list

On one of the clusters at Spil we noticed a sudden increase in the length of the history list and a steep increase in the ibdata file in the MySQL directory.
I did post a bit about this topic earlier regarding MySQL 5.5 but this cluster is still running 5.1 and unfortunately 5.1 does not have the same configurable options to influence the purging of the undo log…

Now I did find a couple of great resources that explain the purge lag problem into detail: Pythian, DimitriK and …

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Storage Engine API state graph

Drizzle still has a number of quirks inherited from the MySQL Storage Engine API (e.g. BLOBs, row buffer, CREATE SELECT and lack of DDL transaction boundaries, key tuple format). One of the things we fixed a long time ago was to have proper methods for StorageEngines to be called for: startTransaction, startStatement, endStatement, commit and rollback.

If you’ve had to implement a transactional storage engine in MySQL you will be well aware of the pattern of “in every …

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Showing entries 1 to 4