Today I read the nice post of Bhuvanesh on the memory leak issue they experienced with MySQL. In fact when you read the post, you realize that MySQL was just following the parameters that were setup (the default of max_prepare_stmt_count is 16382 even on 5.6).

I’m still convinced that the problem should be resolved in the application even if the use of ProxySQL for multiplexing is great.

In MySQL 8.0, we have enabled the …

Has you may already know, in MySQL it is possible to set an expiration period for passwords.

It’s not always obvious to see when the password will expire. And most of the time if you don’t pay much attention you will get something like this:

ERROR 1820 (HY000): You must reset your password using
ALTER USER statement before executing this statement.

Let me share you a small query that check for how long your password is still valid in case it was created with an expiration delay or if the global default_password_lifetime is set on …

Oracle released many new MySQL versions back on Monday, but I had no time during this very busy week to check anything related (besides the fact that MySQL 8.0.13 can be complied from source on my Fedora 27 box). I am sure you've read a lot about MySQL 8.0.13 elsewhere already, even patches contributed by Community are already presented in a separate post by Jesper Krogh.

I am still mostly interested in MySQL 5.7. So, here is my typical quick review of some selected bugs reported in public by MySQL Community users and fixed in MySQL …

Yet another topic I missed in my blog post on problematic MySQL features back in July is MySQL optimizer. Unlike with XA transactions, it was done in purpose, as known bugs, limitations and deficiencies of MySQL optimizer is a topic for a series of blog posts if not a separate blog. At the moment the list of known active bug reports in optimize category consists of …

One of the features I missed in my blog post on problematic MySQL features back in July is XA transactions. Probably I was too much in a hurry, as this feature is known to be somewhat buggy, limited and not widely used outside of Java applications. My first related feature request, Bug #40445 - "Provide C functions library implementing X/OPEN XA interface for Bea Tuxedo", was created almost 10 years ago, based on the issue from one of MySQL/Sun customers of that time. I remember some …

While writing about problematic Oracle MySQL features previously I concentrated mostly on InnoDB problems that I have to fight with really often and deliberately skipped replication from even the preliminary list of features to study in details for that blog post. First of all, I mostly work with MariaDB users now, and implementation of many replication features in MariaDB is notably different already (and has its own list of known problems). But this happened also because (asynchronous) replication plays a key role in most MySQL environments and deserves a detailed study in a separate post.
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Many of you already know how to retrieve the size of your dataset, schemas and tables in MySQL.

To summarize, below are the different queries you can run:

Dataset Size

I the past I was using something like this :

But now with sys schema being installed by default, I encourage you to use some of the formatting functions provided with it. The query to calculate the dataset is now:

SELECT sys.format_bytes(sum(data_length)) DATA,
       sys.format_bytes(sum(index_length)) INDEXES,
       sys.format_bytes(sum(data_length + index_length)) 'TOTAL SIZE'
FROM information_schema.TABLES ORDER  BY data_length + index_length;

Let’s see an example:

Performance_Schema is used most of the time to get metrics about queries and connections. But it can also provide other very useful information.

So today, I will show you how you can see a list of users that didn’t connect to MySQL since we restarted it (since last reboot).

SELECT DISTINCT mu.user FROM mysql.user mu
LEFT JOIN performance_schema.users psu
ON mu.user = psu.user
WHERE psu.user IS NULL
AND mu.user NOT IN ('mysql.infoschema', 'mysql.session', 'mysql.sys')
ORDER BY mu.user;


Example:

mysql> SELECT DISTINCT mu.user FROM mysql.user mu
    ->       LEFT JOIN performance_schema.users psu 
    ->       ON mu.user = psu.user  
    ->       AND mu.user NOT IN ('mysql.infoschema', 'mysql.session', 'mysql.sys') …

More than 2 months passed since my previous review of active MySQL bug reports I am subscribed to, so it's time to describe what I was interested in this summer.

Let's start with few bug reports that really surprised me:

• Bug #91893 - "LOAD DATA INFILE throws error with NOT NULL column defined via SET". The bug was reported yesterday and seem to be about a regression in MySQL 8.0.12 vs older versions. At least I have no problem to use such a way to generate columns for LOAD DATA with MariaDB 10.3.7.
• Bug #91847 - "Assertion `thread_ids.empty()' failed.". As usual, Roel Van de Paar …

Several MySQL releases happened yesterday, but of them all I am mostly interested in MySQL 5.7.23, as MySQL 5.7 (either directly or indirectly, via forks and upstream fixes they merge) is probably the most widely used MySQL GA release at the moment.

In this post (in a typical manner for this "Fun with Bugs" series)  I'd like to describe several bugs reported by MySQL Community users and fixed in MySQL 5.7.23. As usual, I'll try to concentrate mostly on InnoDB, replication, partitioning and optimizer-related bugs (if any).