Sometimes, the MySQL Optimizer chooses a wrong plan, and a query that should execute in less than 0.1 second ends-up running for 12 minutes ! This is not a new problem: bugs about this can be traced back to 2014, and a blog post on the subject dates of 2015. But even if this is old news, because this problem recently came to my attention, it is a problem worth writing on.
This
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At Percona Managed Services, sometimes clients’ applications face deadlock situations and need all historic deadlock information for application tuning.
We could get the LATEST DETECTED DEADLOCK from SHOW ENGINE INNODB STATUS\G:
…. ------------------------ LATEST DETECTED DEADLOCK ------------------------ *** (1) WAITING FOR THIS LOCK TO BE GRANTED: RECORD LOCKS space id 163 page no 3 n bits 72 index GEN_CLUST_INDEX of table `deadlock_test`.`t` trx id 78507 lock_mode X waiting *** (2) TRANSACTION: TRANSACTION 78508, ACTIVE 155 sec starting index read mysql tables in use 1, locked 1 ….
But how could we view all past deadlock information?
We could enable innodb_print_all_deadlocks, and all deadlocks in InnoDB user transactions will be recorded in the MySQL error log.
Let‘s start the test.
Create the test database …
[Read more]Unbelievably, the OpenLampTech developer newsletter is one year old. Thank you so much for reading and making it possible! I appreciate each and every one of you.
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In this week’s OpenLampTech issue #52, we have articles covering:
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[Read more]Hi all,
As you know the CfP for the devroom has been open and you may have noticed that we have only half a day that we also need to share.
Therefore, we will have only 4 sessions and they should look like this:
We didn’t decide yet which of the two colors will be for which project.
Due to the very low number of sessions, we will not attempt to compose a selection committee.
Managing a committee to find the candidates, collect their decisions, communicate and especially ask for votes (and yes often these are very busy people) is a time consuming process.
For the committee, reviewing the proposed sessions is a lengthy procedure and agreeing on 16 sessions is already very complicated so only for 4… …
[Read more]pre-FOSDEM MySQL Days are back for a 5th edition !
With the latest MySQL release (8.0.31), MySQL adds support for the SQL standard INTERSECT and EXCEPT table operators: Let’s have a look how to use them. We will use the following table: CREATE TABLE `new` ( `id` int NOT NULL AUTO_INCREMENT, `name` varchar(20) DEFAULT NULL, `tacos` int DEFAULT NULL, `sushis` int DEFAULT NULL, PRIMARY […]
With the latest MySQL release (8.0.31), MySQL adds support for the SQL standard INTERSECT and EXCEPT table operators.
Hello dear MySQL Community !
As you may already know FOSDEM 2023 is again going to be held in-person. FOSDEM will take place February 4th and 5th 2023.
We have also decided to put our pre-FOSDEM MySQL Day on track for a fifth edition.
As for the last edition, the event will be spread over 2 days.
These 2 extra days related to the world’s most popular open source database will take place just before FOSDEM, the 2nd and 3rd February at the usual location in Brussels.
Please don’t forget to register as soon as possible as you may already know, the seats are limited !
Register on eventbrite: https://mysqldays2023.eventbrite.com
And, please don’t forget, that if you have register for the event and you cannot make it, please free back your ticket …
[Read more]Recently we had a question on getting your Galera Cluster upgraded from MySQL 5.7 to MySQL 8.0. While we have plenty of extensive documentation on Upgrading Galera Cluster, this blog covers the Linux example for a rolling major upgrade (the procedure is documented, but this is more extensive). So we will describe going from MySQL 5.7.23 to MySQL 8.0.28 on one node. We did this on CentOS 7.
Firstly, let’s start by disabling SELinux by executing setenforce 0.
We need to install the appropriate MySQL 5.7 binaries, so we can grab them from releases.galeracluster.com. Since we have decided on MySQL 5.7.23, we should get the packages from …
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