Скачать или смотреть How to Pass Variables to init.sql in Docker's docker-entrypoint-initdb.d

Learn how to dynamically pass variables to your `init.sql` file in Docker containers using `docker-compose` and shell scripts.
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How to Pass Variables to init.sql in Docker's docker-entrypoint-initdb.d

In the world of containerization, passing variables and configuring services is a common challenge. If you're working with PostgreSQL in Docker and you need to initialize your database with a table that should have a dynamic name, you might be wondering how to achieve this effectively. This guide will guide you through the process of passing a variable to your init.sql file using Docker and docker-compose.

Understanding the Problem

When setting up a PostgreSQL database within a Docker container, the docker-entrypoint-initdb.d directory is used to initialize the database with SQL scripts at startup. However, sometimes you need to define certain parameters, like table names, dynamically. In this scenario, you're looking to pass a variable (PG_TABLE) from your Dockerfile to your init.sql file. Here's how you can do that step by step.

Step-by-Step Solution

Step 1: Create Your Dockerfile

First, you will need to set up your Dockerfile to accept build arguments that can be passed during the build process. Here's a simple example of how to define that in your Dockerfile:

[[See Video to Reveal this Text or Code Snippet]]

Step 2: Prepare Your SQL Seed File

Next, set up your SQL file with a placeholder for the table name that will be replaced later:

seed.sql

[[See Video to Reveal this Text or Code Snippet]]

This uses ${PG_TABLE} as a placeholder for the actual table name that will be passed.

Step 3: Create Your Shell Script

You’ll need a shell script that replaces the placeholder in your seed.sql file with the actual value of the variable passed. Here’s an example of how that script might look:

script.sh

[[See Video to Reveal this Text or Code Snippet]]

This script uses the sed command to find and replace the placeholder with the provided argument.

Step 4: Set Up Your Docker Compose File

To build your Docker image and pass the environment variable effectively, you also need to configure your docker-compose.yml:

[[See Video to Reveal this Text or Code Snippet]]

Ensure that the variable PG_TABLE is set in your .env file so it can be correctly parsed during the build.

Final Thoughts

After setting up the Dockerfile, the SQL file, the shell script, and the Docker Compose, you can run your Docker container, and it will initialize the PostgreSQL database with a table name based on the variable you provided. This provides you with a flexible solution for dynamic table names throughout your testing and development processes.

The key takeaway here is that the script.sh was crucial for targeting and modifying the correct seed.sql file located in /docker-entrypoint-initdb.d/.

By following these steps, you should now be able to successfully pass variables to your init.sql during the initialization of your PostgreSQL Docker container.

Happy coding!