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Databricks + Delta Lake MERGE duplicates – Deterministic vs Non-Deterministic ETL.

Is there any problem more classic to the Data Lakes and Data Warehouses than duplicate records? You would think after doing the same ETL for over a decade I could avoid the issue, apparently not. It’s good never to think too highly of one’s self, the duplicates can get us all. Today I want to talk about a wonderful feature of Databricks + Delta Lake MERGE statements that are perfect for quietly and insidiously injecting duplicates into your Data Warehouse or Data Lake. This is a great trick to play on your unsuspecting coworkers.

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End-to-End Pipeline Integration Testing for Databricks + Delta Lake.

The testing never ends. Tests tests tests, and more tests. When it comes to data engineering and data pipelines it seems good practices are finally catching up after years. In the past, the data engineering community took a lot of heat, and rightly so, for not adopting good software engineering principles, especially in data pipelines.

In the defense of many data engineers, because of the varied backgrounds people come from, some were never taught or realized the importance of good software design and testing practices. Sure, it always “takes more time” upfront to design data pipelines with code that is functional and unit-testable, and worse, able to be integration tested from end to end. It requires some foresight and thought in both data architecture and pipeline design to enable complete testability.

Integration testing end-to-end in an automated manner is a tough nut to crack. How can you do such a thing on massive pipelines that crunch hundreds of TBs of data? With a little creativity.

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Part 3 – Data Modeling in Data Warehouses, Data Lakes, and Lake Houses.

Now we are getting to the crux of the matter. I would say Data Modeling is probably one of the most unaddressed, yet important parts of Data Warehousing, Data Lakes, and Lake Houses. It raises the most questions and concerns and is responsible for the rise and fall of many Data Engineers.

This is what really drives the difference between the”big three”, Data Modeling.

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Part 2 – How Technology Platforms affect your Data Warehouse, Data Lake, and Lake Houses.

This is a start of a 5 part series on Demystifying Data Warehouses / Data Lakes / Lake Houses. In Part 2 We are digging into the common Big Data tools and how those technologies have a direct impact on Data Models and what kind of Datastore ends up being designed.

Part 1 – What are Data Warehouses, Data Lakes, and Lake Houses?

Part 2 – How Technology Platforms affect your Data Warehouse, Data Lake, and Lake Houses.

Part 3 – Data Modeling in Data Warehouses, Data Lakes, and Lake Houses.

Part 4 – Keys To Sucess – Idemptoency and Partitioning.

Part 5 – Serving Data from your Data Warehouse, Data Lake, or Lake House.

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5 Part Series – Demystifying Data Warehouses / Data Lakes / Lake Houses

Even I get confused these days. Data Warehouse, Data Lake, and Lake Houses … why do we have three, what are the differences? Is it all just marketing huff-a-luff? Technology and life in the data world seem to be changing fast these days. Lot’s of new vendors on the streets trying to hawk their tools and solutions, each of them pumping out content designed to solve all your data needs.

I’ve seen a lot of content out there by SAAS vendors, and by folks who ascribe to a said vendor, about Data Lakes and Lake Houses, new schema designs and approaches, and it’s hard to know what is just a sales tactic and what is real. I’m going to stir the pot.

This is a start of a 5 part series on Demystifying Data Warehouses / Data Lakes / Lake Houses. Enjoy.

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Hive Metastore in Databricks – What To Know.

Hive is like the zombie apocalypse of the Big Data world, it can’t be killed, it keeps coming back. More specifically the lesser-known Hive Metastore is the little sneaker that has wormed its way into a lot of Big Data tooling and platforms, in a quasi behind the scenes way. Many people don’t realize it, but Hive Metastore is the beating heart behind many systems, including Databricks. It’s one of those topics that sneaks up on you, ignore it happily at your own peril, till all of a sudden you need to know everything about it.

Specifically, I want to talk about Hive MetaStore as related to Databricks, how it works inside the Databricks platform, and what you need to know. I tripped myself up a lot during my initial forays into Databricks at a Production level. When you wander outside the realm of Notebooks, which you should, strange things start to happen. Databricks seems to assume you already have your own Hive Metastore, maybe like the Glue Data Catalog, or that you want to set up your own somewhere. But what if you don’t?

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Lessons Learned from MERGE operations with Billions of Records on Databricks Spark

Something happens with you starting working with 10’s of billions of records and data sets that are hundreds of TBs in size. Do you know what happens? Things stop working, that’s what. I miss the days where 1-10 TBs were considered large and in charge. the good ole days.

I want to talk about lessons learned from working with MERGE INTO using Databricks Sparks. The suggestions, the marketing material, the internet, and what you actually need to do to gain reasonable performance. It’s easy to say … “here … use this new feature, you will get % 50-speed improvements.” Yeah right. Honestly, new features and fancy tricks always help, but typically it comes down to the fundamentals. The “boring” stuff if you will, that make or break Big Data operations.

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CTE vs SubQuery

What to choose what to choose? The age-old problem that has plagued data engineers forever, ok maybe like 10 years, should you use CTE’s or Sub-Queries when writing your SQL code. This has become even more of a relevant topic with the rise of SparkSQL, Snowflake, Redshift, and BigQuery. Funny how some things never change. 15 years ago working on SQL Server I would ask myself the same question.

Are they really that different at all? Is it just a matter of preference? Let’s take a look at a few examples of CTE vs Subquery using SparkSQL as an example and see what we see.

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6 Tips for Optimizing Databricks Cluster and Pipeline Performance and Cost

Databricks, easily the hotest tool these days for Data Lakes and Data Warehousing, it’s a beast. As with any new technology there are always growing pains, learnings, and tips and tricks that might not be obvious to those dipping their toes in the water. Not understand certain concepts, and being unware of specific configurations can cost you time and money very easily when running large ETL pipelines on Databricks.

I want to share 7 tips for Databricks newbies, and oldies, that are foundational to good Data Engineering architecture, affecting both performance and cost.

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Data Modeling – Relational Databases (SQL) vs Data Lake (File Based)

Data Modeling is a topic that never goes away. Sometimes I do reminisce about the good ol’ days of Kimball-style data models, it was so simple, straightforward, just the same thing for years. Then Big Data happened, Spark happened. Things just changed. There is a lot of new content coming out around Data Lakes and data modeling, but it still seems like a fluid topic, with nothing as concrete as the classic Data Warehouse toolkit.

Oh, what to do what to do. I do believe there are a few key ideas and points to being successful with file-based Data Lake modeling. I think it’s a mistake to fully embrace the classic Kimball-style Data Warehouse approach. It really comes down to Relational Database SQL vs File-Based data models are going to be different, for technical and practical reasons.

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