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I didn't know that join reordering is quite interesting, though complex, topic in Apache Spark SQL. The queries not only can be transformed into the ones using JOIN ... ON clauses. They can also be reordered accordingly to the star schema which we'll try to see in this post.
In my previous post I explained how Apache Spark can reorder JOINs based on the logical plan. Today I'll focus on another aspect of reordering which uses cost estimation for the proposed plans.
One of the reasons why I like my blogging activity is that from time to time the exchange is bidirectional. It happens mostly on Github but also on the comments under the post and I appreciate the situation when I don't know the answer and must dig a little to explain it in a blog post :) I wrote this one thanks to bithw1 issue created on my Spark playground repository (thank you for another interesting question btw :)).
Even though I've already written a few posts about Apache Kafka as a data source in Apache Spark Structured Streaming, I still had some questions in my head. In this post I will try to answer them and let this Kafka integration in Spark topic for investigation later.
Containers are with us, data engineers, for several years. The concept was already introduced on YARN but the technology that really made them popular was Docker. In this post I will focus on its recommended practices to make our Apache Spark images better.
When I discovered microk8s I was delighted! An easy installation in very few steps and you can start to play with Kubernetes locally (tried on Ubuntu 16). However, running Apache Spark 2.4.4 on top of microk8s is not an easy piece of cake. In this post I will show you 4 different problems you may encounter, and propose possible solutions.
I've written a lot about data sources, including Apache Kafka. However, Apache Spark is not only about sources but also about targets called sinks. In this post I will focus on Apache Kafka sink integration and try to answer some question in FAQ mode.
On the one hand, I appreciate JSON for its flexibility but also from the other one, I hate it for exactly the same thing. It's particularly painful when you work on a project without good data governance. The most popular pain is an inconsistent field type - Spark can manage that by getting the most common type. Unfortunately, it's a little bit trickier for less common problems, for instance when a same field has different case sensitivity.
Under one of my posts I got an interesting question about ignoring maxPartitionBytes configuration entry by Apache Spark for text-based data sources. In this post I will try to answer it.
When the unit tests work on "your machine" but fail on your colleague's, you know you did something wrong. When the failures are not about test assertions but technical reasons, the "something wrong" transforms into "something strange". And it may happen with Apache Spark as well.
If you've ever wondered why when you write "2019-05-10T20:00", Apache Spark considers it as a timestamp field? The fact of defining it as a TimestampType is one of the reasons, but another question here is, how Apache Spark does the conversion from a string into the timestamp type? I will give you some hints in this blog post.
In my previous post I have shown you the writing and reading parts of my custom state store implementation. Today it's time to cover the data reprocessing and also the limits of the solution.
In my previous post I introduced the classes involved in the interactions with the state store, and also shown the big picture of the implementation. Today it's time to write some code :)
In my last Spark+AI Summit 2019 follow-up posts I'm implementing a custom state store. The extension is inspired by the default state store. At the moment of code analysis, one of the places that intrigued me was the put(key: UnsafeRow, value: UnsafeRow) method. Keep reading if you're curious why.
When I started to think about implementing my own state store, I had an idea to load the state on demand for given key from a distributed and single-digit milliseconds latency store like AWS DynamoDB. However, after analyzing StateStore API and how it's used in different places, I saw it won't be easy.
After my Summit's talk I got an interesting question on "off" for the data reprocessing of sessionization streaming pipeline. I will try to develop the answer I gave in this post.
In this post I will start the customization part of the topics covered during my talk. The first customized class will be the class responsible for the checkpoint management.
One of the points I wanted to cover during my talk but for which I haven't enough time, was the dilemma about using a local deduplication or Apache Spark's dropDuplicates method to not integrate duplicated logs. That will be the topic of this post.
I'm slowly going closer to the end of Spark+AI Summit follow-up posts series. But before I terminated, I owe you an explanation for how to run the pipeline from my Github on Kinesis.
In the first version of my demo application I used Kafka's timestamp field as the watermark. At that moment I was exploring the internals of arbitrary stateful processing so it wasn't a big deal. But just in case if you're wondering what I didn't keep that for the official demo version, I wrote this article.
