Question​

My revisions table lists the following versions:

mysql> SELECT * FROM  "atlas_schema_revisions";
+-------------------------+---------+-----+
| version                 | applied | ... |
+-------------------------+---------+-----+
| .atlas_cloud_identifier | 0       |     |
| 20251007053111          | 1       |     |
| 20251007051222          | 1       |     |
| 20250618084333          | 1       |     |
+-------------------------+---------+-----+

However, when I inspect the target database, the schema changes from 20250618084333 were never applied. How can I delete the latest row(s) so the revision history reflects the actual state?

Question​

How can I keep a single canonical schema or model and apply it to multiple database drivers (for example, an application Postgres database and a data-lake store) so the two remain in sync?

Given a large database schema, how can I manage schema migration for a single table without affecting the rest of the schema?

Answer​

Atlas supports the --include flag (or the env.include attribute) to scope operations to specific resources. If you need to manage the lifecycle of a single table (or a set of tables), use this flag to avoid changes to the rest of the schema.

For example, to manage the products table in a MySQL database:

atlas schema apply \
  --url "mysql://root:pass@:3308/db" \
  --to "file://schema.sql" \
  --dev-url "docker://mysql/8/dev" \
  --include "products"

If the connection URL is not bound to a schema, specify the schema name in the pattern:

atlas schema apply \
  --url "mysql://root:pass@:3308/" \
  --to "file://schema.sql" \
  --dev-url "docker://mysql/8" \
  --include "db.products"

This command will only apply changes related to the products table, leaving other tables untouched.

atlas schema apply \
  --url "mysql://root:pass@:3308/" \
  --to "file://schema.sql" \
  --dev-url "docker://mysql/8" \
  --include "*.products"

Read more:

• Exclude Tables
• URL Connection Scope
• Declarative Schema Migration

How to inspect an external_schema data source (ORM schema) in atlas.hcl to confirm it loaded correctly?

Why does Atlas not detect PostgreSQL event_trigger objects when using --dev-url with search_path=public?

Question​

What encoding is used by Atlas for schema files? How do you avoid encoding issues with PowerShell on Windows?

Answer​

Atlas uses UTF-8 to encode schema files and migration files generated by Atlas. UTF-8 is the default encoding on nearly all system terminals, but on Windows, PowerShell uses UTF-16 by default. This can cause an encoding issue when Atlas loads the schema files generated by the inspect command.

When working with multiple branches and applying hotfixes directly to production, out-of-order migration conflicts may occur if migration files are created with timestamps that don't reflect the actual merge order.

The Problem​

Consider this scenario:

Initial state:

• Master branch:
  • 001_initial.sql
• Dev branch (PR pending):
  • 001_initial.sql
  • 002_add_posts.sql
  • 004_add_index.sql

After hotfix applied directly to production:

• Master branch:
  • 001_initial.sql
  • 003_hotfix_add_email.sql ← hotfix added
• Dev branch (unchanged):
  • 001_initial.sql
  • 002_add_posts.sql
  • 004_add_index.sql

After merging master into dev - the problem:

• 001_initial.sql - Applied to production
• 002_add_posts.sql - Dev-only, not applied to production
• 003_hotfix_add_email.sql - Applied to production
• 004_add_index.sql - Dev-only, not applied to production

This creates a non-linear migration history where migration files 002 and 004 were created before and after the hotfix timestamp but haven't been applied to production.

Question​

When using Atlas on my macOS, I can run atlas migrate apply without any issues, and it applies the migrations successfully. But when running in CI on linux, I get the following error: Error: checksum mismatch

Answer​

This issue is likely due to differences in line endings between operating systems. macOS uses LF (Line Feed) for line endings, while Windows uses CRLF (Carriage Return + Line Feed). When you run Atlas commands in a Docker container, it may be using a different line ending format than what your migrations were created with.

In version control systems like Git, a changeset represents an atomic unit of change. It groups related file modifications under a single hash, allowing them to be reviewed, applied, or reverted together.

In database migrations, a changeset is a unit of schema or data changes made up of SQL statements stored in a migration file, typically executed together in a single transaction.

With Atlas, we advocate for treating migration directories as deployment artifacts resulting from a structured build process. The preferred approach is to push migration directories to the Atlas Schema Registry. In addition to its role as a migration directory storage, the Schema Registry provides a tight integration with the Atlas CLI and the Atlas Cloud UI, allowing you to deploy migrations, visualize schemas over time, review deployment logs and errors, and more.

However, some users prefer to store their migration directories in S3, typically due to internal policies or requirements.