Why Running migrations locally and remotely in Supabase? - Purpose & Use Cases

The Big Idea

What if one simple command could keep your local and cloud databases perfectly matched every time?

The Scenario

Imagine you have a database for your app. You make changes to its structure by hand on your computer, then try to do the same on the cloud server. You have to remember every change and type it again carefully.

The Problem

This manual way is slow and risky. You might forget a step or make a typo. Your app could break because the local and remote databases don't match. Fixing these mistakes takes a lot of time and stress.

The Solution

Running migrations locally and remotely means writing your database changes once and applying them automatically everywhere. This keeps your databases in sync without errors or extra work.

Before vs After

✗ Before

ALTER TABLE users ADD COLUMN age INT;
-- Then manually run the same on remote

✓ After

supabase migration up
-- Applies pending migrations remotely (local via supabase start)

What It Enables

You can update your database safely and quickly, whether on your computer or in the cloud, without worrying about mistakes.

Real Life Example

A developer updates the user profile table to add a new field. They run the migration command once, and both their local setup and the live app's database update perfectly in sync.

Key Takeaways

Manual database updates are slow and error-prone.

Migrations automate and sync changes locally and remotely.

This saves time and prevents app-breaking mistakes.

Practice

1. What is the main reason to run database migrations locally before running them remotely?

easy

A. To update the live database directly without testing

B. To test changes safely before applying them to the live database

C. To delete all existing data before migration

D. To backup the remote database automatically

Solution

1. Step 1: Understand migration purpose locally

   Running migrations locally allows you to check if changes work without risk to live data.

2. Step 2: Understand migration purpose remotely

   Running migrations remotely updates the live database after testing is successful.

3. Final Answer:

   To test changes safely before applying them to the live database -> Option B

4. Quick Check:

   Test locally first = Safe migration [OK]

Hint: Always test migrations locally before live update [OK]

Common Mistakes:

• Running migrations directly on live without testing
• Assuming local migrations update remote automatically
• Thinking migrations delete all data by default

2. Which command correctly runs migrations on your local Supabase project?

easy

A. supabase db reset

B. supabase db push

C. supabase db migrate

D. supabase migration run

Solution

1. Step 1: Identify the correct Supabase CLI command

   The command supabase db reset applies all migrations to the local database by resetting it.

2. Step 2: Check other options

   supabase migration run and supabase db migrate are invalid; supabase db push updates the remote database.

3. Final Answer:

   supabase db reset -> Option A

4. Quick Check:

   Local migration command = supabase db reset [OK]

Hint: Use 'supabase db reset' to run and test local migrations [OK]

Common Mistakes:

• Using remote commands like 'supabase db push' for local
• Using incorrect commands like 'supabase migration run'
• Trying to run migrations without Supabase CLI installed

3. Given this sequence of commands, what is the expected result?

supabase db push
supabase db remote commit
supabase db remote apply

medium

A. The commands will cause an error due to invalid syntax

B. Migrations are only applied locally, remote stays unchanged

C. Remote migrations are applied without local testing

D. Migrations are applied locally and then committed and applied remotely

Solution

1. Step 1: Analyze each command

   supabase db push applies local schema changes to remote; supabase db remote commit generates a migration from remote schema differences; supabase db remote apply applies pending migrations on remote.

2. Step 2: Understand the flow

   All commands target the remote database; no local application occurs in this sequence.

3. Final Answer:

   Remote migrations are applied without local testing -> Option C

4. Quick Check:

   db push + remote commit/apply = remote only [OK]

Hint: db push + remote commit/apply affects remote without local changes [OK]

Common Mistakes:

• Thinking 'supabase db push' applies locally
• Expecting local database changes from remote commands
• Believing commands have invalid syntax

4. You ran supabase db reset locally but forgot to run supabase db remote apply. What issue will you face?

medium

A. Local database will reset to remote state

B. Remote database will automatically update

C. Migration files will be deleted

D. Local and remote databases will be out of sync

Solution

1. Step 1: Understand local reset effect

   supabase db reset reapplies all migrations to the local database only.

2. Step 2: Understand remote apply necessity

   Without supabase db remote apply, the remote database remains unchanged, causing out-of-sync databases.

3. Final Answer:

   Local and remote databases will be out of sync -> Option D

4. Quick Check:

   Missing remote apply = databases out of sync [OK]

Hint: Always run remote apply after local reset to sync [OK]

Common Mistakes:

• Assuming remote updates automatically after local reset
• Thinking local reset affects remote database
• Believing migration files get deleted after reset

5. You want to update your live Supabase database with a new table but keep your local database unchanged for now. Which approach is correct?

hard

A. Run supabase db remote apply without running supabase db reset

B. Run supabase db push only

C. Run supabase db push then supabase db remote apply

D. Run supabase db reset locally then supabase db remote apply

Solution

1. Step 1: Understand local vs remote migration commands

   supabase db reset affects local; supabase db remote apply applies pending migrations to remote only.

2. Step 2: Apply only remote changes

   Create/edit migration file for new table, then run supabase db remote apply; skip local commands like supabase db reset.

3. Final Answer:

   Run supabase db remote apply without running supabase db reset -> Option A

4. Quick Check:

   Remote apply only = live DB updated, local unchanged [OK]

Hint: Use remote apply after creating migration file to update only remote [OK]

Common Mistakes:

• Running local reset or push which updates local DB unnecessarily
• Resetting local DB when not needed
• Assuming remote apply requires local reset first