I would like to share my trip to Romania/Bucharest for User Group Leaders summit.
It was really great meeting. Great people, talks, discussions, food and etc.
I want to create same atmosphere in Azerbaijan/Baku next year
Here are some of the photos:

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I would like to inform community, as an Azerbaijan MySQL User Group leader I have attanded to E-Days-2016 and talked about MySQL, Open Source and the power of “BUG”s
Here are some photos from meetup:

Oh, there is a cool new feature added? And you are going to implement and use it?
Well, the brain of Bug lover is not working in that way, for me new feature is cool in terms of playing. It is a new place where hunt season is opened suddenly

Currently I am in Percona Live 2016 and you can catch me every time -> my name is some sort of pain to pronounce but you can just say Shako instead of Shahriyar.

Yesterday there was an interesting discussion about bug reports and in general what is a “Bug” and how i can identify that if it is a Bug or not?
Here are general rules:

1. Trust in yourself. If somebody says that, hey it is an expected behaviour, just do not believe. Go ahead and fill a report. Insist in your opinion at last it will be converted to DOC issue, pretty valid DOC Bug -> …

As doc states:

https://dev.mysql.com/doc/refman/5.7/en/innodb-page-compression.html

To disable page compression, set COMPRESSION=None using ALTER TABLE. Writes to the tablespace that occur after setting COMPRESSION=None no longer use page compression. To uncompress existing pages, you must rebuild the table using OPTIMIZE TABLE after setting COMPRESSION=None.

ALTER TABLE t1 COMPRESSION="None";
OPTIMZE TABLE t1;

With regular table there is no table rebuild:

mysql> alter table sbtest4 compression='none';
Query OK, 0 rows affected (0,01 sec)
Records: 0 Duplicates: 0 Warnings: 0

So the rebuild will be on optimize table run.

But if you want table rebuild each time when you run compression=’none’ you can add encryption=’N’ option

Azerbaijan MySQL User Group next meeting was with IT girls from “WoWoman” division in Baku.
We have talked about Linux and MySQL.
There was a hands-on lab about installing Ubuntu, working with basic Linux commands.

I would like to share some photos from this event

This post is about situation where comments in BUG reports are really valuable in term of learning and getting some internal view of going process.
Let’s take a look at -> http://bugs.mysql.com/bug.php?id=80183

The report is about how you can not drop general tablespace if it was a crash of MySQL instant while running alter statement.


mysql> create tablespace ts1 add datafile '/var/lib/mysql_tablespaces/ts1.ibd' engine=innodb;
Query OK, 0 rows affected (0,02 sec)

Kill -9 process while altering:


mysql> alter table sbtest1 tablespace ts1;
ERROR 2013 (HY000): Lost connection to MySQL server during query

CREATE TABLE `sbtest1` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`k` int(10) unsigned NOT NULL DEFAULT '0',
`c` char(120) NOT NULL …

If you are running ‘OPTIMIZE TABLE’ or altering ‘TABLESPACE’ just be careful not to kill MySQL service while running these commands
Here is a test case:
We have a table:

CREATE TABLE `sbtest1` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`k` int(10) unsigned NOT NULL DEFAULT '0',
`c` char(120) NOT NULL DEFAULT '',
`pad` char(60) NOT NULL DEFAULT '',
PRIMARY KEY (`id`),
KEY `k_1` (`k`)
) ENGINE=InnoDB AUTO_INCREMENT=2427738 DEFAULT CHARSET=latin1 COMPRESSION='lz4'

After a while we want to ‘OPTIMIZE’ this table:

mysql> optimize table sbtest1;
ERROR 2013 (HY000): Lost connection to MySQL server during query

Uups MySQL process was killed/crashed.

[root@ps-5 mysql]# ls -l dbtest/
total 1092792
-rw-r-----. 1 mysql mysql 65 фев 4 03:43 db.opt
-rw-r-----. 1 mysql mysql …

If you have not be careful with General Tablespaces in MySQL 5.7.10, you must be at least from now.
I have reported several bugs related to General Tablespaces for eg.:

* #77814 -> Altering table twice,with same tablespace will increase general tablespace size (verfied)

* #77556 -> Segmentation fault while creating general tablespace in disk full Linux (fixed/closed)

* #77830 -> “ALGORITHM=INPLACE is not supported” no error with tablespace alter (open)

* #80070 -> allocated_size and file_size differ if create general tablespace outside datadir (verified)

* …

Recently i have figured out that we can over-allocate InnoDB buffer pool size as I have already reported:

#79850

So as a result I can start MySQL with 300GB buffer pool size in my 16G laptop.

Config:

innodb_buffer_pool_size=300G
innodb_buffer_pool_instances=64

Started as:

2016-01-05 15:23:58 16211 [Note] InnoDB: Initializing buffer pool, size = 300.0G
2016-01-05 15:24:31 16211 [Note] InnoDB: Completed initialization of buffer pool

If you think that it is not harmful, let’s examine another report:

#79880

With MySQL 5.7.10 in my VM on CentOS 7:

I have:

[root@mysql-57 ~]# free -m
total used free shared buff/cache available
Mem: 3428 …

Recently, we have discussed BUGs with our local community members. Where the half off people said that, they have seen “Assertion Failure” errors in error log. And the question was what is this at all?

In general “assert” is a code portion put by developer to handle certain things.

Well, i am not a core MySQL developer and my C/C++ knowledge is limited to simple calculator But i will try to explain where all these “Assertion Failure” errors come up.
The exact reason of failing Assertion/crash should be known by core developers. I know how to crash, they know how to fix. You help developers to reproduce a crash filling a bug report, by uploading test cases or maybe the core dump, backtrace etc.
Say, for eg, if you try to create a view after getting “full disk” error you will crash MySQL. See related BUG report -> …