DBT : Leveraging DBT Macros : Macro that dynamically adjusts the S3 bucket path


Leveraging DBT Macros for Environment-Specific S3 Bucket Paths: A Detailed Guide

Data analytics is all about working smart, not just working hard. In data analytics, we often find ourselves working in multiple environments – development, user acceptance testing (UAT), and production (prod). However, changing code manually to adapt to these different environments can be both time-consuming and error-prone.

For instance, suppose you’re working with different AWS S3 buckets for each environment. In that case, you don’t want to be manually changing your bucket paths every time you switch environments.

This is where DBT (Data Build Tool) shines. DBT is a transformation tool that allows data analysts and engineers to transform data in their warehouses more effectively. One of its features is macros, which you can use to generate reusable pieces of code.

In this article, we will create a DBT macro that dynamically adjusts the S3 bucket path based on the environment. With this macro, you won’t need to change the code, regardless of the environment where it runs.

Understanding DBT Macros

DBT macros are snippets of code written in Jinja, a templating language for Python. They allow for code reuse and can dramatically reduce the redundancy in your SQL codebase.

Macros are defined using the {% macro %} and {% endmacro %} tags and can accept arguments. They are then called using the {% call %} tag or the {{ macro_name() }} syntax.

Creating the getDBT Macro

Let’s create a macro named getDBT that will return the appropriate S3 bucket path based on the provided environment. We will assume that the environment value is stored in the DBT profile configuration.

The bucket names have the following format: s3://freshers-in-dataanalytics-{env}-raw-data, where {env} is the name of the environment.

{% macro getDBT() %}
  {% set env = target.name %} {# Fetching the environment name from DBT target configuration #}
  {% if env == 'dev' %} {# If the environment is 'dev' #}
  {% elif env == 'uat' %} {# If the environment is 'uat' #}
  {% elif env == 'prod' %} {# If the environment is 'prod' #}
  {% else %} {# If the environment is not recognized #}
    Invalid environment. Check DBT target configuration.
  {% endif %}
{% endmacro %}

Using the getDBT Macro

Now that we have defined our getDBT macro, we can use it in our SQL code. For instance:

FROM "{{ getDBT() }}/freshers_in_data_viewers_file_20230715.csv"

The above SQL statement will fetch data from a file named my_file.csv located in the appropriate S3 bucket depending on the current environment.

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