crdb-change

name	crdb-change
description	Generate CockroachDB SQL and migrations for schema changes. Use when creating migrations, updating the database schema, or when the user mentions migrations, schema changes, or dbinit.sql.

CockroachDB database changes

Generate database changes for this repository. This includes changes to:

• schema/crdb/dbinit.sql
• Migrations for changes

Instructions

Follow these steps in order. Do not skip ahead.

Step 0: Read the README

You MUST read schema/crdb/README.adoc first. Pay attention to important instructions and limitations, such as the requirement for idempotency and the inability to rename columns.

Step 1: Ascertain the scope of the request

If not already provided, prompt the user whether they'd like to:

• Perform both a dbinit.sql change and a migration: If this is the case, then:
  1. Ask the user to describe the changes they'd like to perform to dbinit.sql.
  2. Make those changes, asking the user followup questions as necessary.
  3. Go directly to step 3, with the scope of the migration being to cover those changes.
• Write migrations for pre-existing changes: In this case, changes need to be fetched from version control. Go to step 2.

Step 2: Get the diff

Check if .jj exists in the repository to determine whether to use jj or git commands.

Prompt the user to ask where the schema changes are:

• Uncommitted changes: Changes not yet committed.

  • git: git diff -- schema/crdb/dbinit.sql (unstaged) or git diff --cached -- schema/crdb/dbinit.sql (staged)
  • jj: jj diff -- schema/crdb/dbinit.sql

• This commit only (stacked diff workflow): Changes are in the current commit only.

  • git: git diff HEAD^ -- schema/crdb/dbinit.sql
  • jj: jj diff --from @-- -- schema/crdb/dbinit.sql

• This branch (feature branch workflow): Changes span the entire branch.

  • git: git diff $(git merge-base HEAD main) -- schema/crdb/dbinit.sql
  • jj: jj diff --from 'fork_point(trunk() | @)' -- schema/crdb/dbinit.sql

If the diff doesn't show anything, ask the user which ref to diff from.

Step 3: Create migration folder

Create a new folder under schema/crdb/ using the provided name or a short descriptive name derived from the schema changes.

Use existing folder names in schema/crdb/ as examples for naming conventions.

NOTE: The numbered folders, e.g. 1.0.0, are for legacy support only. No additional numbered directories should be added.

Step 4: Write migration files

Based on the diff from step 1, write migration files in order:

• Use up01.sql, up02.sql etc. (zero-padded) if you have more than 10 files.
• Use up1.sql, up2.sql etc. if you have 10 or fewer files.
• For Data Definition Language (DDL) statements, one statement per file!
• For Data Modifying Language (DML) statements, multiple statements are allowed per file.
• For ALTER TABLE with multiple columns, you can add them all in one statement.
• When adding NOT NULL columns to existing tables, add temporary defaults, then remove them in later migration files.
• Use IF NOT EXISTS for idempotency where supported.
• Individual up.sql files are executed within a transaction (this always happens), and should be idempotent (this is an expectation that the migration author must uphold, with, e.g. IF NOT EXISTS).

Step 5: Update dbinit.sql version

Bump the version number at the end of schema/crdb/dbinit.sql.

Step 6: Update SCHEMA_VERSION

In nexus/db-model/src/schema_versions.rs, bump SCHEMA_VERSION.

Step 7: Add to KNOWN_VERSIONS

In nexus/db-model/src/schema_versions.rs, add the new version to the KNOWN_VERSIONS list.

Step 8: Generate verification files

Run EXPECTORATE=overwrite cargo nextest run -p nexus-db-model 'test_migration_verification_files' to auto-generate .verify.sql files for any migration steps that contain backfill-prone DDL (CREATE INDEX, ADD CONSTRAINT, ALTER COLUMN SET NOT NULL, or ADD COLUMN with NOT NULL / non-null DEFAULT / STORED computed columns). Check in any generated files alongside the migration. If your migration doesn't contain backfill-prone DDL, no files are generated and this step is a no-op.

Step 9: Test the migration

Run cargo nextest run -p omicron-nexus schema to verify that the migration is correct.

Common issues

• Don't guess table names—use the diff from step 1 to find the correct table.
• When adding constraints, always use IF NOT EXISTS for idempotency.
• For columns with defaults in migration but not in final schema, add the defaults during migration then remove them.
• Don't skip step 1—always run the diff command first to understand what needs to be migrated.

Data migration tests

When creating a migration that affects existing data (like adding columns to existing tables), also add a data migration test in nexus/tests/integration_tests/schema.rs:

• Add before_X_0_0 function to create test data in the old format.
• Add after_X_0_0 function to verify the migration worked correctly.
• Add the version to the get_migration_checks() map.

This ensures old rows can be migrated smoothly in production.