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ILshat Khamitov
ILshat Khamitov

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Lite version of Flyway migrator for PostgreSQL in TypeScript

#typescript #postgres #database #node

Description

In my projects, I always use Flyway to manage database migrations, including some important components of its ecosystem:

  1. Versioned migrations are standard migrations that are applied sequentially one after another.

  2. Repeatable migrations are repeatable migrations, such as scripts for creating procedures. They allow you to track the history of changes using Git.

  3. Callbacks are various hooks that are triggered at a specific time. For example, you can create a script beforeMigrate__init_types.sql, which describes all the custom types used in the database. The migrator first executes this script, and then the rest of the operations.

Since my projects are mostly based on Node.js, I use a Node.js wrapper for Flyway — node-flywaydb. This tool is very easy to use: when launched, it downloads the original Java utility and runs it, so it requires a JVM on the machine to work.

Problem

When we build Docker images intended for running database migrations, we have to include JVM in them, which significantly increases the image size and slows down the whole CI/CD process.

Possible solutions

  1. Use Node.js-migrants (for example: db-migrate, umzug, pg-migrate).
  2. Use migrators built into the ORM used in the project (for example: prisma, typeorm).
  3. Write a lightweight clone of Flyway in Node.js for one database type (PostgreSQL).

The decision made

Since I actively use the features of Flyway, such as repeatable migrations and callbacks, and do not want to give them up, and there are no analogues of these functions in other migration systems, I decided to write my own lightweight clone of Flyway in Node.js for PostgreSQL, which was done.

Development stages

  1. Versioned migrations — done.
  2. Repeatable migrations — done.
  3. Callbacks — partially done, for versioned only.
  4. Flyway schema history table - partially completed, only for versioned and repeatable.
  5. Migration Command Dry Runs - completed.
  6. Baseline migrations - not completed.
  7. Undo migrations - not completed.

  8. Script migrations — not implemented.

  9. Migration transaction handling — not implemented.

There they really have a lot of interesting features, I listed only those that were most useful in my practice.

Example of use

Starting the database

To start the database, run the following command:

curl -fsSL https://raw.githubusercontent.com/EndyKaufman/pg-tools/refs/heads/master/docker-compose.yml -o docker-compose.yml
docker compose up -d
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The result will be a successful launch of the PostgreSQL container:

[+] Running 3/3
 ✔ Network pg-tools_default              Created                         0.1s
 ✔ Volume "pg-tools-postgre-sql-volume"  Created                         0.0s
 ✔ Container pg-tools-postgre-sql        Started                         0.2s
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Create a migration

To create your first migration, run the following command:

npx pg-flyway create --name=Init --version=1
echo "CREATE TABLE \"User\"(id uuid NOT NULL DEFAULT uuid_generate_v4() constraint PK_USER primary key,email varchar(20));" > migrations/V1__Init.sql
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The result will be a successful creation of an empty migration:

[2025-01-15T23:23:53.903] [INFO] CreateEmptyMigrationService - Name: Init
[2025-01-15T23:23:53.904] [INFO] CreateEmptyMigrationService - Locations: migrations
[2025-01-15T23:23:53.914] [INFO] CreateEmptyMigrationService - Migration "migrations/V1__Init.sql" was created successfully!
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Applying the migration

To apply the created migration, run the following command:

npx pg-flyway migrate --database-url=postgres://pgtoolsusername:pgtoolspassword@localhost:5432/pgtoolsdatabase?schema=public
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The result will be a successful migration:

[2025-01-16T00:08:39.052] [INFO] MigrateService - Locations: migrations
[2025-01-16T00:08:39.053] [INFO] MigrateService - HistoryTable: __migrations
[2025-01-16T00:08:39.053] [INFO] MigrateService - DatabaseUrl: postgres://pgtoolsusername:pgtoolspassword@localhost:5432/pgtoolsdatabase?schema=public
[2025-01-16T00:08:39.074] [INFO] MigrateService - Migrations: 1
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Viewing a list of completed migrations

To view a list of completed migrations, run the following command:

npx pg-flyway info --database-url=postgres://pgtoolsusername:pgtoolspassword@localhost:5432/pgtoolsdatabase?schema=public
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The result will be a table with information about the completed migrations:

[2025-01-16T09:15:34.007] [INFO] info - HistoryTable: __migrations
[2025-01-16T09:15:34.008] [INFO] info - DatabaseUrl: postgres://pgtoolsusername:pgtoolspassword@localhost:5432/pgtoolsdatabase?schema=public
[2025-01-16T09:15:34.057] [INFO] info - Migrations: 1
┌───────────┬─────────┬─────────────┬──────┬─────────────────────┬─────────┬──────────┐
│  Category │ Version │ Description │ Type │        Installed On │   State │ Undoable │
├───────────┼─────────┼─────────────┼──────┼─────────────────────┼─────────┼──────────┤
│ Versioned │       1 │        Init │  SQL │ 2025-01-15 20:08:39 │ Success │       No │
└───────────┴─────────┴─────────────┴──────┴─────────────────────┴─────────┴──────────┘
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Stopping the database

To stop the database, run the following command:

docker compose down
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Plans

The main functions of Flyway have already been ported to Typescript code, which provides the necessary functionality for most scenarios when working with migrations.

I plan to port the remaining unported functions as soon as I have free time.

I will be glad to pull requests with new functions and bug fixes.

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