Errors and Bugs, MySQL

MySQL won’t start [ERROR] Found option without preceding group in config file

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Hey folks,

have you ever received a call for a MySQL on windows that stopped working after someone did something at their my.cnf? Then you try to start the service by cmd and get the following error.

mysqld: [ERROR] Found option without preceding group in config file C:\ProgramData\MySQL\MySQL Server 8.0\my.ini at line 1.
mysqld: [ERROR] Fatal error in defaults handling. Program aborted!

Well, for some reason, the editor that was used (no idea which one was), threw some random byte at the beginning of the file. To solve that (on windows at least), open the file on Notepad++, go to Format > Convert to ANSI. Save the file and start again the service.

What was the weirdest thing that happened to you on a Windows Server?

Backup and Restore, Errors and Bugs, MySQL

MySQL Error1075 – Incorrect table definition; What’s happening?

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Hey Folks,

A few months ago, I found an issue, where, for some reason, someone ignored the warnings and tried to restore a backup from a different version of MySQL (or even MariaDB, IDK). And as a result, half the database was running without Primary Keys. So when a system was trying to update their schema, we were getting errors (like the error bellow) trowed at our face.

1075 - Incorrect table definition; there can be only one auto column and it must be defined as a key

Ok, first things first, you would like to run an ALTER TABLE TABLE_NAME_HERE
ADD PRIMARY KEY (ID); and see if it works.  The error was being thrown because the table key doesn’t have a single index on it… if you have problems with duplicated records on it, you can try the following script to solve the issue.

First, get the max id from the table, and then run the following: 

UPDATE TABLE_NAME_HERE JOIN (SELECT @sequence := MAX_ID_HERE ) r SET id=@sequence:=@sequence+1 where id= DUPLICATED_ID_HERE;

WARNING

Be aware that, if the rows that were duplicated, where referenced as FK on another table, you will get some headache (well, you already have problems…) !!

Database, MySQL

MySQL Error ‘Unknown or incorrect time zone’ at a replica

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Have you ever tried to do a MySQL replication at a different timezone/SO and got the following error message at SHOW REPLICA STATUS? Well, there are two ways to solve this, Error ‘Unknown or incorrect time zone: ‘America/Cuiaba” on query. Default database: ‘glpi_tiab’. Query: ‘BEGIN’

If you are on Linux, you can run the following and solve the problem (after a restart of the service).

$ mysql_tzinfo_to_sql /usr/share/zoneinfo | mysql -u root mysql -p

On Windows, I found it to be easier if you download the timezone instead of build/import your own. You can download from here https://dev.mysql.com/downloads/timezones.html.

use mysql;
source /path/to/file/timezone_posix.sql;

Well, that’s it for today. See ya.

SQL | PLSQL, SQLServer

Retrieve the SQL Server Version from a Backup File

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Have you ever been in the need to retrieve the SQL Server version that was used on a backup file?

Well, if for some weird reason that happens to you, the following SQL can help you. It won’t restore the database, it’ll just retrieve some basic info about it.

With that, you’ll have the DatabaseVersion (Internal Number Version) where the backup was from. You can also grab some useful information like the Server Name, Creation Date, and more.

RESTORE HEADERONLY FROM DISK = N'b:\backup\data_backup.bak'

Below we have a table of  Versions x Internal Number.

Version Internal Number Version Compat. Level
SQL Server 2019 895 – 904 150
SQL Server 2017 868 – 869 140
SQL Server 2016 852 130
SQL Server 2014 782 120
SQL Server 2012 706 110

I hope it helps!

Database, Errors and Bugs

19c+ DBMS_STATS.GATHER_TABLE_STATS Memory Leaking on PGA

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Hi all,

So, here is a quick post but which wasn’t so eaasy to be mapped, though.

It happens that right after a 19c upgrade from 18c, we started facing Memory Leak messages related to PGA area on a regular basis. After a while following the v$process_memory allocation, it was possible to map it to an ODI routing with DBMS_STATS.GATHER_TABLE_STATS. The PGA exceeds the limit just a few minutes after.

Nice han, so what is happening?

Long story short: Bug 30846782 : 19C+ FAST/EXCESSIVE PGA GROWTH WHEN USING DBMS_STATS.GATHER_TABLE_STATS.

According to Oracle Docs: No Workaround!

But here is the golden info I want to share after an SR:

EXECUTE IMMEDIATE 'alter session set "_fix_control"='20424684:OFF';

You are welcome!

Cheers!

SQLServer, Tools

How to send Telegram messages from SQL Server

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Hi folks,
You usually receive notifications from SQLServer at your e-mail, right? A nice way to receive updates from your SQL Server Schedule job, it’s sending them through telegram. To do so, you’ll have to configure one additional step and choose Operating System (CmdExec) as a type of command. And to call the Telegram API, we can use a PowerShell command like the following:

powershell "Invoke-RestMethod -Uri 'https://api.telegram.org/bot{API-KEY}/sendMessage?chat_id={CHAT-ID}&text={TEXT}'"

Just replace the following keys with the proper value (don’t forget to remove the curly brackets too).

API-KEY: Your bot API key
CHAT-ID: The ID of the chat where you’ll receive the message, could be a single user, or a chat group
TEXT: Your beloved message.

What else do you use to achieve this kind of alers? Slack? healthchecks.io? Tell us 😉

Career, Community, grepOra

Thanks GoldenTalks!

 

Hi all,

I want to first say thanks for Gilson and his whole team in GoldenGateBR for the very pleasant time on last Thursday’s conversation!

We spoke a bit of everything, but mostly over career, my historic on the community, and of course the grepOra blog.

Also many thanks for the ones who could connect and stay connected up to the end of the video. Here is the recording, if you will (it’s in Portuguese!).

Java | DevOps | APEX | Scripts

Microsoft Ignite – Certification Voucher

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Hey folks,

Do you enjoy learning new things? Between September 22 and September 24, Microsoft will be hosting their yearly Microsoft Ignite event. Of course, it’ll be online this time and free of charge :).

This year, you can earn a certification voucher and that’s awesome. You’ll be able to choose one certification from a specific list. Check the list of available certifications and the Terms and Conditions accessing the following link: https://docs.microsoft.com/pt-br/learn/certifications/microsoft-ignite-cloud-skills-challenge-2020-free-certification-exam.

Database, Performance

Plan Stability: SQLs switching to Bad Plans (HPV) and Load Very High (12c+)

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Hi all,

That’s not the first post about this topic. Please read this one first.

Thing is: I access this post soooo often, as I face this sort of issue sooo frequently I decided to make a new one with some updated info. Even because, 3 years ago I wrote this article for 12.1 databases, now we have some relevant changes to 12.2 onwards.

Ok, so, for a little bit of context from the previous post:

  • After some critical issues with Plan Stability (new HSP being created out of nowhere very often) I mapped this to the usage of Adaptive Query Features.
  • At that point, I had a match to the latchfree events and mapped it specifically to latch misses on “Result Cache: RC Latch”.
  • As per MOS at the time, when Automatic Dynamic Sampling is used for the SQL statements, it can decide, based upon these statistics, that a better response time could be achieved by using the result cache for those queries. This can cause heavy usage of the result cache leading to the contention on latch free for “Result Cache: RC Latch”
  • So the villain was the Automatic Dynamic Sampling, as part to the SQL Plan Directives.
  • On the following months and migrations I started seeing more and more issues related to the SQL Plan Directives as part of the Adaptive Query Optimization features. So, I have been following the referred steps more and more.
  • Happens this means setting a few underscore parameters, which we should avoid unless approved/recommended by Oracle, so I’ve been trying to be less intrusive and simply disabling the whole Adaptive Features.
  • How to do it? That’s the tricky part and the thing to keep in mind, as we had changes from 12.1 to 12.2

Some words about the parameters settings:

  • The parameter “optimizer_adaptive_features” is a valid parameter for 12.1 and it’s enabled by default. I recommend leaving it as FALSE if you are facing this sort of issues.
  • This parameter is obsolete con 12.2 onwards though. It was replaced by both optimizer_adaptive_statistics and optimizer_adaptive_plans.
    • 12.1:

adap1

    • 12.2+:

adap2

(images from https://blogs.oracle.com/optimizer/optimizer-adaptive-features-in-oracle-database-12c-release-2)

  • Also, keep one eye on all %optim% parameters, as specific mechanisms can be enabled (for some reason) as I recently faced in a client ( _optimizer_adaptive_plan = TRUE).

When Adaptive Queries are good?

Ok Matheus, but if we should disable it, why did Oracle created in the first place?

Well, if something would be always bad, it would be disabled by default… There are some good usage cases: Dynamic Sampling is typically recommended when you know you are getting a bad execution plan due to complex predicates.

“oh, noice, so I’ll change on my database I have a lot of complex queries” . Don’t, I suggest you to try and use an alter session statement to set the value for optimizer_dynamic_sampling parameter as it can be extremely difficult to come up with a system-wide setting. And you can mess up with other things.

When Adaptive Queries are bad?

If the queries compile times need to be as fast as possible, for example, unrepeated OLTP queries where you can’t amortize the additional cost of compilation over many executions. Serial statements are typically short running and any Dynamic Sampling overhead at compile time can have a large impact on overall system performance (if statements are frequently hard parsed).

For systems that match this profile, setting OAF=FALSE is recommended. For Oracle Database 12c Release 2 onwards, using the default OAS=FALSE is recommended.

I hope this helps you!