Data Quality checks in ETL Processes

There is always an exponentially increase in cost is associated with finding software defects in the later stages of the development lifecycle. In data warehousing, this is compounded because of the additional business costs of using incorrect data to make critical business decisions. So the early detection of these system defects is prioritized as critical checks along with which a regular process of doing continuous testing using a CI pipeline. And can this be implemented?

Maintaining Quality in ETL projects is a very complex process because of many reasons. It depends on the complexity of the system which is in development and in use. Typically huge amounts of data are handled in an ETL pipeline or in a data orchestration systems and data often comes from multiple sources which need to be combined, transformed and then loaded to target schemas. During the initial setup of client systems in production, it will be loaded as a full load and then the scheduled load runs on an ongoing basis (daily, nightly, weekly/monthly loads) is treated as incremental/delta loads.

ETL work-flows involves all kinds of complex calculations and transformations on the data based on client needs. And how often these calculations/transformation methods remain to be the same and do they make similar patterns? some can have similarity and often it changes based on the client needs. If we can trace out all the minor to major patterns, similarities and occurring in this entire process of loading data to target schemas from the extracts, then it is possible to accommodate a test suite that validates these checks on a regular basis, whereby which it is possible to find defects report them and maintain quality integrated with the system on a regular basis.

There are several advanced tools available for software testing, but testing ETLs is something completely different. Tools dedicated to ETL testing exist but mostly paid tools and paid tools will not be an evolved tool. There are open-source tools in the market but mature ones are still rare. In Many IT industries, ETL systems are mostly tested manually, which is very labor-intensive and prone to errors. Running the tests manually without a dedicated tool to schedule them, also prevents these tests from being automated.

However, as for any IT project, recurrent testing is important to be able to guarantee a high level of quality embedded with the customer’s data and the software systems that they use for storing these data. The…