Andreas Andreakis, Ioannis Papapanagiotou

Overview

Change-Data-Capture (CDC) allows capturing committed changes from a database in real-time and propagating those changes to downstream consumers [1][2]. CDC is becoming increasingly popular for use cases that require keeping multiple heterogeneous datastores in sync (like MySQL and ElasticSearch) and addresses challenges that exist with traditional techniques like dual-writes and distributed transactions [3][4].

In databases like MySQL and PostgreSQL, transaction logs are the source of CDC events. As transaction logs typically have limited retention, they aren’t guaranteed to contain the full history of changes. Therefore, dumps are needed to capture the full state of a source. There are several open source CDC projects, …

In MySQL and Oracle, you set a session variable quite differently. That means you should expect there differences between setting a session variable in Postgres. This blog post lets you see how to set them in all three databases. I’m always curious what people think but I’m willing to bet that MySQL is the simplest approach. Postgres is a bit more complex because you must use a function call, but Oracle is the most complex.

The difference between MySQL and Postgres is an “@” symbol versus a current_setting() function call. Oracle is more complex because it involves the mechanics in Oracle’s sqlplus shell, SQL dialect, and PL/SQL language (required to assign a value to a variable).

MySQL

MySQL lets you declare a session variable in one step and use it one way in a SQL statement or stored procedure.

1. You set a session variable on a single line with the following …

IS NULL, IS NOT NULL, truthiness among other assertions on MySQL and PostgreSQL

People like to complain about JavaScript, how can one thing be equal to the other, i.e. null == undefined evaluates to true unless you use the triple equals ===. Other dynamic typed languages have its peculiarities, such as Ruby where 0 == true evaluates to true, the reason for Ruby is that considers 0 as a value and any value evaluates to true.

How about SQL? The answer is… it depends.

Which database are you using?

Some may be more forgiving, like MySQL doing casts for you all over the place, or more strict like PostgreSQL where you can only compare the truthiness of something of the same type.

From driver and rider locations and destinations, to restaurant orders and payment transactions, every interaction on Uber’s transportation platform is driven by data. Data powers Uber’s global marketplace, enabling more reliable and seamless user experiences across our products for riders, …

The post Databook: Turning Big Data into Knowledge with Metadata at Uber appeared first on Uber Engineering Blog.

via GIPHY I was at a dinner party recently, and talking with some colleagues. I had worked with them years back on Oracle systems. One colleague Maria said she really enjoyed my newsletter. Join 38,000 others and follow Sean Hull on twitter @hullsean. She went on to say how much has changed in the last …

Continue reading "How is automation impacting the dba role?"

In this blog post, I’ll look at a comparison of PostgreSQL and MySQL.

I came across a post from Hans-Juergen Schoenig, a Postgres consultant at Cybertec. In it, he dismissed MySQL and showed Postgres as better. While his post ignores most of the reasons why MySQL is better, I will focus on where his post is less than accurate. Testing for MySQL was done with Percona Server 5.7, defaults.

Mr. Schoenig complains that MySQL changes data types automatically. He claims inserting 1234.5678 into a numeric(4, 2) column on Postgres produces an error, and that MySQL just rounds the number to fit. In my testing I found this to be a false claim:

mysql> CREATE TABLE data (
    -> id    integer NOT NULL, …

SQLite is really a good tool to set up quick proof of concepts and small applications; however it’s not the most robust solution on the market for working with relational databases. In the open source community two databases take the top of the list: PostgreSQL and MySQL.

I did a small project for my studies. I was using SQLite as I didn’t need much out of it. Curious, I decided to see how the application would behave on other databases and decided to try PostgreSQL and MySQL. I had two problems to solve, and this post is about the first one: how to deal with the migrations. They were as follows:

Active Record automatically put the field id in all of its tables, that’s why it is omitted on the migrations.

In PostgreSQL it …

via GIPHY Amazon releases a new database offering every other day. It sure isn’t easy to keep up. Join 35,000 others and follow Sean Hull on twitter @hullsean. Let’s say you’re hiring a devops & you want to suss out their database knowledge? Or you’re hiring a professional services firm or freelance consultant. Whatever the … Continue reading How to interview an amazon database expert →

With tons of new No-SQL database offerings everyday, developers & architects have a lot of options. Cassandra, Mongodb, Couchdb, Dynamodb & Firebase to name a few. Join 33,000 others and follow Sean Hull on twitter @hullsean. What’s more in the data warehouse space, you have Hadoop, which can churn through terabytes of data and get … Continue reading Will SQL just die already? →

Here’s the behind-the-scenes story about how Uber Engineering’s Driver Team continues to develop our virtual onboarding funnel to get hundreds of thousands of driver-partners on the road earning money with Uber.

The Consequences of Scale for Driver-Partners

Our team cares …

The post How Uber Engineering Massively Scaled Global Driver Onboarding appeared first on Uber Engineering Blog.