Hydronitrogen Tech Blog

Hamel Ajay Kothari writes about computers and stuff.



Apache Spark Shuffles Explained In Depth

I originally intended this to be a much longer post about memory in Spark, but I figured it would be useful to just talk about Shuffles generally so that I could brush over it in the Memory discussion and just make it a bit more digestible. Shuffles are one of the most memory/network intensive parts of most Spark jobs so it's important to understand when they occur and what's going on when you're trying …


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In the Code: Spark SQL Query Planning and Execution

If you've dug around into the Spark SQL code, whether it's in catalyst, or the core code, you've probably seen tons of references to Logical and Physical plans. These are the core units of query planning, a common concept in database programming. In this post we're going to go over what these are at a high level and then how they're represented and used in Spark. The query planning code is especially important because it …


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Writing a Spark Data Source

Note: This is being written as of early December of 2015 and currently assumes Spark 1.5.2 API. The data sources API has been out for a few versions now but it's still stabilizing so some of this might change to be out of date.

I'm writing this guide as part of my own exploration on how to write a data source using the Spark SQL Data Sources API. We'll start with exploration of …


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