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Category: ETL

Checking JSON Structure with ADF

Rayis Imayev takes us through the solution of a tricky problem in Azure Data Factory:

Within my “ForEach” container I have also placed a Stored Procedure task and set 4 data elements from my incoming data stream as values for corresponding parameters.

However this approach will not work for all my incoming JSON events, it actually failed for the last one, since it didn’t have both “stop_time” and “last_update” data elements.

An easy way to fix this problem is to add missing data elements with empty values for the last event record, however, when we don’t have control over incoming data, we need to adjust our data processing steps.

Read on to see how Rayis solves this problem.

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Tying Azure Data Factory to Source Control

Eddy Djaja explains why you really want to tie Azure Data Factory to your source control:

Azure Data Factory (ADF) is Microsoft’s ETL or more precise: ELT tool in the cloud. For more information of ADF, Microsoft puts the introduction of ADF in this link: https://docs.microsoft.com/en-us/azure/data-factory/introduction. As some have argued if ADF will replace or complement the “on-premise”  SSIS, it is uncertain and only time can tell what will happen in the future.
Unlike SSIS, the authoring of ADF does not use Visual Studio. ADF authoring uses a web browser to create ADF components, such as pipelines, activities, datasets, etc. The simplicity of authoring ADF may confuse the novice developers on how ADF components are saved, stored and published. When logging to ADF for the first time after creating an ADF, the authoring is in the ADF mode. How do we know?

Click through for the explanation and some resources on how to do it.

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Auto-Detecting Column Delimiters with Data Factory

Mark Kromer shows us a way of dynamically learning what the likely delimiter of a delimited file is:

Processing delimited text files in the data lake is one of the most popular uses of Azure Data Factory (ADF). To define the field delimiter, you set the column delimiter property in an ADF dataset.

The reality of data processing is that delimiter can change often. ADF provides a facility to account for this data drift via parameterization. However, this assumes that you know that the delimiter is changing and what it will change to.

I’m going to briefly describe a sample of how to auto-detect a file delimiter using ADF Data Flows.

Click through for the demo.

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Transforming JSON to CSV with Azure Data Factory

Rayis Imayev shows how to use the Flatten task with Azure Data Factory wrangling data flows:

Last week I blogged about using Mapping Data Flows to flatten sourcing JSON file into a flat CSV dataset:
Part 1Transforming JSON to CSV with the help of Flatten task in Azure Data Factory

Today I would like to explore the capabilities of the Wrangling Data Flows in ADF to flatten the very same sourcing JSON dataset.

Click through to see what’s different.

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Transforming JSON to CSV with Azure Data Factory

Rayis Imayev shows how you can use the Flatten task in Azure Data Factory to convert JSON text to CSV:

What this new task does it helps to transform/transpose/flatten your JSON structure into a denormalized flatten datasets that you can upload into a new or existing flat database table. 

I like the analogy of the Transpose function in Excel that helps to rotate your vertical set of data pairs (name : value) into a table with the column names and values for corresponding objects. And when this vertical JSON structural set contains several similar sets (array) then ADF Mapping Data Flows Flatten does a really good job by transforming it into a table with several rows (records).

Click through for a demonstration.

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ADF.PROCFWK 1.1 Released

Paul Andrew has a new name for the metadata-driven framework in Azure Data Factory:

Hi data friends! Version 1.1 of my ADF.procfwk is ready!

Following the great response I got to the version 1.0 blog series I decided to push ahead and get version 1.1 out there as soon as possible. The main thing I’ve addressed with this release is the big problem of having hard coded service principal credentials in the body of the Azure Function request that called our execution pipelines. Hopefully we can all agree this was/is not great for a number of reasons.

Read on for more details including a detailed changelog, and check out the GitHub repo.

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Loading Data from CSVs with Inconsistent Quoted Identifiers

Dave Mason has some fun with loading data from files:

BCP and OPENROWSET are long-lived SQL Server options for working with data in external files. I’ve blogged about OPENROWSET, including a recent article showing a way to deal with quoted data. One of the shortcomings I’ve never been able to overcome is an inconsistent data file with data fields in some rows enclosed in double quotes, but not all. I’ve never found a way around this limitation.

Let’s demonstrate with BCP. Below is a sample data file I’ll attempt to load into a SQL Server table. Note the data fields highlighted in yellow, which are enclosed in double quotes and contain the field terminator , (comma) character. For reference, the file is also available on Github.

I get unduly frustrated with the implementations of various data loaders around SQL Server and how they handle quoted identifiers differently. And don’t get me started on PolyBase.

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Metadata-Driven ADF Pipelines

Paul Andrew wraps up a series on metadata-driven processing of Azure Data Factory pipelines. Part 3 covers the ADF wrapper necessary for our custom pipelines:

Firstly, to help guide this post below is a mock up of our Data Factory pipelines and activities to show the end goal. Hopefully this view informs how things are going to be connected using what I call a pipeline hierarchy system and how they will work in the overall framework. For our metadata processing framework we can make the following category distinctions about the activities represented:

Grandparent – This is the top level orchestration of our wider data platform solution. Here a scheduled trigger could be connected or processing in our solution grouped into natural areas. Technically this level isn’t required for our processing framework, but I’ve included it as good practice.
Parent – Our parent pipelines primary purpose (try saying that fast 3 times 🙂 ) is to handle the stages of our processing framework. The stages will then be passed off sequentially to our child pipeline using another execute pipeline activity.
Child – At this level in the framework the child is hitting the Azure Function to call the lowest level executors, or the pipelines that we want to actually do the work in our data platform solution. In my previous post I added some example metadata to call pipelines name Stage X-X. These in turn relate to a set of empty place holder pipelines that contained only Wait activities.

Part 4 puts it all together:

For the end to end run of the framework we have a few options to see progress once its been triggered. Before that its worth pointing out that in the below I’ve used the sample metadata provided with the database scripts in GitHub. Then for each execution pipeline I’ve added a single Wait activity with a random time delay of a few seconds. The point here is to test the framework execution, not the pipelines being called. To further clarify, the Stage X-X pipelines names should be replaced with your actual pipeline names in your data platform solution.

Definitely worth the read.

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Building Metadata for an ADF Pipeline

Paul Andrew continues a series on Azure Data Factory and metadata-driven pipelines:

Welcome back friends to part 2 of this 4 part blog series. In this post we are going to deliver on some of the design points we covered in part 1 by building the database to house our processing framework metadata.

Let’s start with a nice new shiny Azure SQLDB database and schema. This can easily be scaled up as our calls from Data Factory increase and ultimately the solution we are using the framework for grows.

Soon we will get to see the Azure Data Factory power in action.

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Incremental Imports with Sqoop

Jon Morisi continues a series on Sqoop:

In my last two blog posts I walked through how to use Sqoop to perform full imports.  Nightly full imports with overwrite has it’s place for small tables like dimension tables.  However, in real-world scenarios you’re also going to want a way to import only the delta values since the last time an import was run.  Sqoop offers two ways to perform incremental imports: append and lastmodified.

Both incremental imports can be run manually or created as job using the “sqoop job” command.  When running incremental imports manually from the command line the “–last-value” arg is used to specify the reference value for the check-column.  Alternately sqoop jobs track the “check-column” in the job and the value of the check-column is used for subsequent job runs as the where predicate in the SQL statement.  I.E. select columns from table where check-column > (last-max-check-column-value).

This is where Sqoop starts to break down for me, and Jon lists some of the issues in the post.

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