DBT : Handling Late-Arriving Data in DBT


Data warehousing and business intelligence often involve working with data that arrives after a certain time period has already been processed. This type of data is called late-arriving data, and it can cause problems when trying to maintain an accurate and up-to-date picture of the data. In this article, we will explain how to handle late-arriving data in DBT (Data Build Tool), a data transformation tool that helps users build and manage their data warehousing pipelines.

  1. Understanding Late-Arriving Data

Late-arriving data is data that arrives after a certain time period, such as a day or a week, has already been processed. For example, if you are running a daily ETL process, late-arriving data could be any data that arrives after the daily process has completed but before the next process starts. This data can come from a variety of sources, such as data sources that were down during the original processing time or data sources that have just recently become available.

Late-arriving data refers to information that arrives after a scheduled processing window, like a daily ETL run. This data might stem from sources that were temporarily inaccessible or newly accessible, causing it to arrive outside the regular processing cycle.

  1. Approaches to Handling Late-Arriving Data

There are several approaches to handling late-arriving data, each with its own pros and cons. Some common approaches include:

  • Ignoring Late Data: This approach is the simplest, but it can result in missing data in your final data set.
  • Processing Late Data Separately: This approach involves processing late data separately from the regular data, and then merging the two data sets together. This approach can be time-consuming and may result in data integrity issues.
  • Updating the Previous Data: This approach involves updating the previous data set with the late-arriving data, which can result in a more accurate picture of the data. However, it can also result in data quality issues if the late data is incorrect or outdated.
  1. Handling Late-Arriving Data in DBT

DBT provides several features that make it easy to handle late-arriving data in your data warehousing pipeline. Some of these features include:

  • Incremental Models: DBT allows you to create incremental models, which only update the data that has changed since the last time the model was run. This makes it easy to incorporate late-arriving data into your data set without having to re-process the entire data set.
  • Scheduling: DBT provides flexible scheduling options, allowing you to run your ETL processes at specific times or on specific days. This makes it easy to incorporate late-arriving data into your data set by running your processes at a time when the late data is available.

Materialized Views: DBT provides materialized views, which allow you to store the results of a query in a table, making it easier to access and analyze the data. You can use materialized views to create a view of your data that includes the late-arriving data, making it easier to analyze and incorporate into your analysis.

  • Re-Running Models: DBT also allows you to re-run models, which can be useful for updating your data set with late-arriving data. You can schedule your models to run at specific times or on specific days to ensure that your data set is always up-to-date.
  1. Best Practices for Handling Late-Arriving Data in DBT

When handling late-arriving data in DBT, it’s important to keep the following best practices in mind:

  • Monitor Data Quality: Regularly monitor the quality of your late-arriving data to ensure that it meets your data quality standards.
  • Document Your Processes: Document your processes for handling late-arriving data, including when your processes run and how you incorporate the late data into your data set.
  • Test Your Processes: Regularly test your processes for handling late-arriving data to ensure that they are working as intended.
  • Automate Where Possible: Automate as much of your process for handling late-arriving data as possible to reduce the risk of errors and improve efficiency.

In conclusion, handling late-arriving data in DBT can be a challenge, but it’s important for ensuring the accuracy and completeness of your data set. By using the features and best practices provided by DBT, you can handle late-arriving data in a way that is efficient, effective, and reliable.

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