Category: Article

I don’t know Ops, and that may be OK

I am a Software Engineer at heart. I started as such and worked with PHP for about 7 years, always correlating my work with data somehow until I got an opportunity and decided to follow my instincts and be a Data Engineer.

I didn’t turn a Data Engineer from one night to another. It was a process. I was lucky to have a boss that noticed my skills with data and decided to give me room to play with it.

But the Ops part, was never my forte and this is why.

Data Integrity

This is my main concern. I am more worried about keeping consistency as much as possible and even in many times choosing it over performance.

Another trait I have is to be always looking for logic errors that may generate bad data into an application. I despise badly written models and have had a bit of problem when working with RDBMS and ActiveRecord. My take on it is: if you have a complex business model, what is easy may become painful. Also, there is no silver bullet solution, you don’t need to use only one technology.

But I won’t go into what is better, what is better it is what it works for you and make you application works and don’t let your users down while maintaining your data integrity.


Your software is not valuable 99% of the times. Your software it is a means to an end. It is a path to interpret business logic and generate value to your company. And if your data sucks (duplicated records, lack of foreign key checks, extreme denormalization in the main DB if relational) you may have no real value at all.

Why don’t I know it?

When I needed doing ops, managing database servers, they were all single servers, at most a read replica on AWS, or only one slave.

One can say I’ve never needed actually to know it. I got lucky having good people working with me on the DevOps team, and we trusted each other’s work, in the end the managers would prefer to use my abilities in another area.

As I said before I do know it’s an area I need to improve, but it is ok to not know it, because even with me not being an expert on it my value lies in understanding the data, the data model and how application handles on data. As a DBA main job usually is to keep the database servers healthy, mine is to keep data itself as a valuable as possible to a company.

Not a DBA

What I do it is many times considered a DBA job, there are a couple areas where both can overlap but I try as a Data Engineer to support the Developers and the Business as a DevOps person do.

You may notice on my posts: I don’t write about replication, cluster, etc. One reason is: I have never in real life have to deal with this particular area deeply. I do know I should know more about that. But one thing is to set it up a couple servers on the cloud with no real data to analyze and performance issues to attend than doing it in real life. However, that doesn’t lessen my value.

I know how to prepare data, I do ETL’s, I do data modeling, I do deep research on which storage would be the best for a case scenario, I help to define policies around migrations and data access, for instance.

My Goal

My goal is to help developers. It’s to help them do the right thing regarding to data as they do regarding with test coverage and code quality.

Everybody reviews code, I rarely seem people reviewing data models. And I want to help to create a culture where people see data as their true value. Remember this: data leaks are more valuable than “code” leaks and potentially more devastating too. So please, let me help you.

MySQL version poll: a not so scientific analysis

MySQL version poll: a not so scientific analysis

Prior to my talk at LaraconEU 2016 I was curious to know how much adoption for MySQL 5.7 was in within the community.

I tweeted this:

Twitter polls only gives you up to 4 items to choose. What I wanted to know is if people were using MariaDB or other forks like Percona, but I didn’t had the proper space, and I  only put three options.

This January I managed to get a bit more syndication on my tweet and more people replied. I added a 4th option, “Other”. This option could include the fork data as well as people using even the MySQL 4:

Analysis results

This have no scientific foundation whatsoever. Most of the people on my twitter bubble work on tech and try to be using cutting edge technology, but I could see a bit of a trend (taking into the consideration also the amount of people that now replied).

August 2016 January 2017

It is possible to notice that 5.7 got more market where 5.5 was the most common version to those people. I would like to think they upgraded first to 5.6 to then upgrade to 5.7 and not just jumped versions disabling and doing this to make it work:

SET @@GLOBAL.sql_mode = '';

Again, this is the equivalent of disabling errors in any language because you are not gonna fix them, just want swipe under the carpet. Don’t do that.

It is nice to see that 5.5 is losing ground (again, a pinch of salt here) to newer and modern versions.

What should I not consider?

Well, you can actually ignore the whole poll as a trend indicator. The first one ran only for a day and it got 85 votes with not all options on it, and the second one had 669 votes and it was a week long poll. Plus the fact there is no way to do a control group to calculate the error margin.

What does this really mean?

MySQL 5.7 was released with General Availability around October 2015, major hosting  and cloud companies started to make it available on February/March 2016. Adoption always take a bit of a time to be absorbed, specially if you have to do any code change to support the new version of the database (hint, you probably will have to). It also means that those companies may at any point stop providing support for versions older than 5.6 (5.5, 5.1, etc.).

Also take into consideration that MySQL 8.0 is under development and most of the strictness embedded by default on 5.7 will continue to come on 8.0. So if you are reading this blogpost and starting a new project, go ahead and start with 5.7 already so when version 8.0 comes out you won’t have trouble upgrading.

If you have a legacy application then, there are ways of adapting your code so you can enjoy everything the new version has to offer. Just a final reminder, disabling strictness on the server to be able to use the JSON feature may sound as a smart idea in the beginning, but that also means putting your data consistency at risk.

What MySQL 8.0.1 means to you as a Developer

This post will be updated as soon more information comes along.

This developer version wasn’t released yet, when it does, use at your own risk.

Oracle released the development version of MySQL 8.0.0-dmr on September 12th of 2016. Since then, the team have been working on the 8.0.1 development milestone. You can find the partial change list here.

The objective here is try to explain how this will have any real world impact for you from 8.0.1. Please remember though, that any changes made to this version will not be final until the General Availability (date not currently set).

These topics are aimed at the Software Engineering side and not DBA and this is why Replication, for instance, is not covered here.


Charset and Collation

MySQL 8.0 was defined as to have utf8mb4 as the default CHARACTER SET and utf8mb4_general_ci as the default COLLATION. 8.0.1 will change the default COLLATION to utf8mb4_0900_ai_ci.

Let’s analyse the name utf8mb4_0900_ai_ci:

How does that impact you? It means that by default, new tables will have that collation and will be able to handle more characters than Basic Multilingual Plane (more emoji! 🤦🏼‍♀️), plus it will be accent and case insensitive. If you want case and accent sensitive you will need to use utf8mb4_0900_as_cs.

If you wish to know more about the reasons for utf8 now being utf8mb4 you should read this post on MySQL official blog: Sushi = Beer ?! An introduction of UTF8 support in MySQL 8.0

Language Specific Charsets

There are cases where language takes precedence over the default general collation. For this you will need to use, for example in the instance of German phone book order, utf8mb4_de_pb_0900_as_cs.


Descending Index

This particularly is one of my most desired features. Finally being implemented on this version, the ALTER TABLE ADD INDEX ix_column (column DESC) won’t be parsed as ASC anymore.

Since InnoDB uses BTREE indexes, when running a query that uses it in the case of single columns it doesn’t matter if the index is ASC or DESC. The index is used for DESC anyway.

However when working with multi-column indexes this will matter and having a descending index will actually increase your performance. Example:

A generic table users:

Field Type Null Key Default Extra
id int(10) unsigned NO PRI auto_increment
first_name varchar(127) NO
last_name varchar(128) NO
email varchar(255) NO
created_at timestamp NO CURRENT_TIMESTAMP
updated_at timestamp NO CURRENT_TIMESTAMP on update CURRENT_TIMESTAMP

The following query will have better performance if run with DESC index on updated_at time column:

FROM `users`
ORDER BY updated_at DESC, first_name ASC
LIMIT 100;

For that we need the following index:

ADD INDEX `ix_updated_at_first_name`
(updated_at DESC, first_name ASC);

Before that, the query plan would do a full scan on the table and not use the index at all. After the index is created it searches on index, and not the table:

Before After
Before After

The query above is just a simplistic example and doesn’t filter anywhere the index, this is why it causes to do a full index scan.


I personally never made use for \N to indicate NULL in any query itself, but I have used it in CSV or TSV files.
This behaviour won’t be supported anymore.
This change won’t impact file import or export through LOAD DATA INFILE or SELECT ... INTO OUTFILE.


In-place operations

In MySQL 5.7 the Generated Columns feature was added. However ALTER TABLE in tables containing one would be a COPY operation (which is slower since it has to copy all data again of the table). Now it can be INPLACE as long as the column(s) being modified is not in a generated column. What this actually means is: the metadata for the column will be changed in real time, without the need to internally create a new table and copy data.



Two new functions are added to aggregate JSON values: JSON_ARRAYAGG() and JSON_OBJECTAGG().

JSON_ARRAYAGG() takes a column or expression as an argument and aggregates the result in a single JSON array.
With JSON_OBJECTAGG(id, col) you can use two columns which will be interpreted as key and value and returns a single JSON object.


Performance on JSON columns when used with ORDER BY was improved. Before MySQL would allocate 1K of memory to a sort key, making it fixed length. The extra padding was removed in this version.

Error Handling

The indexing of JSON fields is only possible through Generated Columns. If you tried to index a JSON field before, would get the following as an error:

JSON column '%s' cannot be used in key specification.

The error message has now been made clearer:

JSON column '%s' supports indexing only via generated columns on a specified JSON path.


More than 100 bugs were fixed on this version. It ranges from InnoDB through Replication and even compilation bugs. The list is too big to be tacked on to this article, but the complete (and yet partial) change list is available here.