Unable to run pg_dump from Supabase

I intend to backup my postgres database at Supabase

$ pg_dump -h db.PROJECT_REF.supabase.co -U postgres --clean --schema-only > supabase_backup.sql

I ran the command

GRANT ALL ON ALL SEQUENCES IN SCHEMA auth TO postgres; 
grant all on auth.identities to postgres, dashboard_user;

Yet, I still get

pg_dump: error: query failed: ERROR:  permission denied for table schema_migrations

pg_dump: error: query was: LOCK TABLE realtime.schema_migrations IN ACCESS SHARE MODE

Solution

EDIT Oct-2022: There's a new/improved script to perform database migration:

Before you begin:

Install Postgres so you can run psql and pg_dump.
Create a new Supabase project.
Store the old project's database URL as $OLD_DB_URL and the new project's as $NEW_DB_URL.

Migrating the database:

Enable Database Webhooks in your new project if you enabled them in your old project.
In your new project, enable all extensions that were enabled in your old project.

Run the following command from your terminal:

#!/usr/bin/env bash

#Edit here:
OLD_DB_URL=db.old_project_ref.supabase.co
NEW_DB_URL=db.new_project_ref.supabase.co
OLD_DB_PASS=secret_password_here
NEW_DB_PASS=secret_new_password_here

#Script:
# Default case for Linux sed, just use "-i"
sedi=(-i)
case "$(uname)" in
  # For macOS, use two parameters
  Darwin*) sedi=(-i "")
esac

PGPASSWORD="$OLD_DB_PASS" pg_dump -d postgres -U postgres \
  --clean \
  --if-exists \
  --quote-all-identifiers \
  --exclude-table-data 'storage.objects' \
  --exclude-schema 'extensions|graphql|graphql_public|net|pgbouncer|pgsodium|pgsodium_masks|realtime|supabase_functions|pg_toast|pg_catalog|pg_*|information_schema' \
  --schema '*' \
  -h "$OLD_DB_URL" > dump.sql

sed "${sedi[@]}" -e 's/^DROP SCHEMA IF EXISTS "auth";$/-- DROP SCHEMA IF EXISTS "auth";/' dump.sql
sed "${sedi[@]}" -e's/^DROP SCHEMA IF EXISTS "storage";$/-- DROP SCHEMA IF EXISTS "storage";/' dump.sql
sed "${sedi[@]}" -e 's/^CREATE SCHEMA "auth";$/-- CREATE SCHEMA "auth";/' dump.sql
sed "${sedi[@]}" -e 's/^CREATE SCHEMA "storage";$/-- CREATE SCHEMA "storage";/' dump.sql
sed "${sedi[@]}" -e 's/^ALTER DEFAULT PRIVILEGES FOR ROLE "supabase_admin"/-- ALTER DEFAULT PRIVILEGES FOR ROLE "supabase_admin"/' dump.sql


PGPASSWORD="$NEW_DB_PASS" psql -d postgres -U postgres \
  --variable ON_ERROR_STOP=1 \
  --file dump.sql \
  -h "$NEW_DB_URL" -p 6543

OLD ANSWER (obsolete):

I believed you may have missed the part to alter the role in the migration guide. I've copied the instructions below:

Before you begin

Make sure Postgres is installed so you can run psql and pg_dump.
Create a new Supabase project.
If you enabled Function Hooks on your old project, enable it on your new project.
Store the old project's database URL as $OLD_DB_URL and the new project's as $NEW_DB_URL.

Migrate the database

Run ALTER ROLE postgres SUPERUSER in the old project's SQL editor
Run pg_dump --clean --if-exists --quote-all-identifiers -h $OLD_DB_URL -U postgres > dump.sql from your terminal
Run ALTER ROLE postgres NOSUPERUSER in the old project's SQL editor
Run ALTER ROLE postgres SUPERUSER in the new project's SQL editor
Run psql -h $NEW_DB_URL -U postgres -f dump.sql from your terminal
Run TRUNCATE storage.objects in the new project's SQL editor
Run ALTER ROLE postgres NOSUPERUSER in the new project's SQL editor