Migrate from Neon to PlanetScale
Use this guide to migrate an existing Neon database to PlanetScale for Postgres.
This guide will cover a no-downtime approach to migrating using Postgres logical replication. If you are willing to tolerate downtime during a maintenance window, you may also use pg_dump
and restore. The pg_dump
/restore approach is simpler, but is only for applications where downtime is acceptable.
These instructions work for all versions of Postgres that support logical replication (version 10+) If you have an older version you want to bring to PlanetScale, contact us for guidance.
Before beginning a migration, you should check our extensions documentation to ensure that all of the extensions you rely on will work on PlanetScale.
As an alternative to this guide, you can also try our Postgres migration scripts. These allow you to automate some of the manual steps that we describe in this guide.
1. Prepare your PlanetScale database
Go to app.planetscale.com
and create a new database. A few things to check when configuring your database:
- Ensure you select the correct cloud region. You typically want to use the same region that you deploy your other application infrastructure to.
- This guide assumes you are migrating from a Neon database, so also choose the Postgres option in PlanetScale.
- Choose the best storage option for your needs. For applications needing high-performance and low-latency I/O, use PlanetScale Metal. For applications that need more flexible storage options or smaller compute instances, choose "Elastic Block Storage" or "Persistent Disk."
Once the database is created and ready, navigate to your dashboard and click the "Connect" button.
From here, follow the instructions to create a new default role. This role will act as your admin role, with the highest level of privileges.
Though you may use this one for your migration, we recommend you use a separate role with lesser privileges for your migration and general database connections.
To create a new role, navigate to the Role management page in your database settings. Click "New role" and give the role a memorable name. By default, pg_read_all_data
and pg_write_all_data
are enabled. In addition to these, enable pg_create_subscription
and postgres
, and then create the role.
Copy the password and all other connection credentials into environment variables for later use:
PLANETSCALE_USERNAME=pscale_api_XXXXXXXXXX.XXXXXXXXXX PLANETSCALE_PASSWORD=pscale_pw_XXXXXXXXXXXXXXXXXXXXXXX PLANETSCALE_HOST=XXXX.pg.psdb.cloud PLANETSCALE_DBNAME=postgres
We also recommend that you increase max_worker_processes
for the duration of the migration, in order to speed up data copying. Go to the "Parameters" tab of the "Cluster configuration" page:
On this page, increase this value from the default of 4
to 10
or more:
You can decrease these values after the migration is complete.
2. Prepare the Neon database
You will need to enable logical replication to use this import guide. To do so, go to the settings page in your Neon project:
Navigate to the "Logical Replication" section and ensure it is enabled.
Warning
Note the warnings in the Neon dashboard. Changing this setting will sever all existing connections and restart all computes.
You can confirm that the wal_level
is set to logical
by running SHOW wal_level;
on your Neon database:
neondb=> SHOW wal_level; wal_level ----------- logical
If you see a result other than logical
, then it is not configured correctly. Once this is enabled, return to the dashboard.
For these instructions, you'll need to connect to Neon with a role that has permissions to create replication publications and read all data. Your default role that was generated by Neon when you first created your database should suffice here. To get these connection credentials to use for the migration, click on the "Connect" button from your project dashboard:
In the connection modal that appears, ensure you have "connection pooling" disabled.
The credentials displayed here are the ones you can use for the migration. For the rest of this guide, we'll assume these are saved into the following environment variables:
NEON_USERNAME=XXXX NEON_PASSWORD=XXXX NEON_HOST=XXX NEON_DBNAME=XXX
3. Copy schema from Neon to PlanetScale
Before we begin migrating data, we first must copy the schema from Neon to PlanetScale. We do this as a distinct set of steps using pg_dump
.
Warning
You should not make any schema changes during the migration process. You may continue to select, insert, update, and delete data, keeping your application fully online during this process.
Run the below command to take a snapshot of the schema for the $NEON_DBNAME
database that you want to migrate:
PGPASSWORD=$NEON_PASSWORD \ pg_dump -h $NEON_HOST \ -p 5432 \ -U $NEON_USERNAME \ -d $NEON_DBNAME \ --schema-only \ --no-owner \ --no-privileges \ -f schema.sql
This saves the schema into a file named schema.sql
.
Note
The above command will dump the tables for all schemas in the current database. If you want to migrate only one specific schema, you can add the --schema=SCHEMA_NAME
option.
The schema then needs to be loaded into your new PlanetScale database:
PGPASSWORD=$PLANETSCALE_PASSWORD \ psql -h $PLANETSCALE_HOST \ -p 5432 \ -U $PLANETSCALE_USERNAME \ -d $PLANETSCALE_DBNAME \ -f schema.sql
In the output of this command, you might see some error messages of the form:
psql:schema.sql:LINE: ERROR: DESCRIPTION
You should inspect these to see if they are of any concern. You can reach out to our support if you need assistance at this step.
4. Set up logical replication
We now must create a PUBLICATION
on Neon that the PlanetScale database can subscribe to for data copying and replication.
To create a publication for all tables in all schemas of the current database, connect to the Neon database:
PGPASSWORD=$NEON_PASSWORD \ PGSSLMODE=require \ PGCHANNELBINDING=require \ psql \ -h $NEON_HOST \ -U $NEON_USERNAME \ -p 5432 \ $NEON_DBNAME
Then run the following command:
CREATE PUBLICATION replicate_to_planetscale FOR ALL TABLES;
You should see this output if it created correctly:
CREATE PUBLICATION
Note
To publish changes for only one specific schema, run the following query:
SELECT 'CREATE PUBLICATION replicate_to_planetscale FOR TABLE ' || string_agg(format('%I.%I', schemaname, tablename), ', ') || ';' FROM pg_tables WHERE schemaname = 'YOUR_SCHEMA_NAME';
This will generate a query that looks like this:
CREATE PUBLICATION replicate_to_planetscale FOR TABLE public.table_1, public.table_2, ... public.table_n;
You can then copy/paste this and execute on Neon. This will create a publication that only publishes changes for the tables in YOUR_SCHEMA_NAME
After creating the publication on Neon, we need to tell PlanetScale to SUBSCRIBE
to this publication.
PGPASSWORD=$PLANETSCALE_PASSWORD psql \ -h $PLANETSCALE_HOST \ -U $PLANETSCALE_USERNAME \ -p 5432 $PLANETSCALE_DBNAME \ -c " CREATE SUBSCRIPTION replicate_from_neon CONNECTION 'host=$NEON_HOST dbname=$NEON_DBNAME user=$NEON_USERNAME password=$NEON_PASSWORD sslmode=require channel_binding=require' PUBLICATION replicate_to_planetscale WITH (copy_data = true);"
Data copying and replication will begin at this point. To check in on the row counts for the tables, you can run a query like this on your source and target databases:
SELECT table_name, row_count FROM ( SELECT 'table_name_1' as table_name, COUNT(*) as row_count FROM table_name_1 UNION ALL SELECT 'table_name_2', COUNT(*) FROM table_name_2 UNION ALL ... SELECT 'table_name_N', COUNT(*) FROM table_name_N ) t ORDER BY table_name;
When the row counts match (or nearly match) you can begin testing and prepare for your application to cutover to use PlanetScale.
5. Handling sequences
Logical replication is great at migrating all of your data over to PlanetScale. However, logical replication does not synchronize the nextval
values for sequences in your database. Sequences are often used for things like auto incrementing IDs, so it's important to ensure we update this before you switch your traffic to PlanetScale.
You can see all of the sequences and their corresponding nextval
s on your source Neon database using this command:
SELECT schemaname, sequencename, last_value + increment_by AS next_value FROM pg_sequences;
An example output from this command:
schemaname | sequencename | next_value ------------+------------------+------------ public | users_id_seq | 105 public | posts_id_seq | 1417 public | followers_id_seq | 3014
What this means is that we have three sequences in our database. In this case, they are all being used for auto-incrementing primary keys. The nextval
for the users_id_seq
is 105, the nextval
for the posts_id_seq
is 1417, and the nextval
for the followers_id_seq
is 3014. If you run the same query on your new PlanetScale database, you'll see something like:
schemaname | sequencename | next_value ------------+------------------+------------ public | users_id_seq | 0 public | posts_id_seq | 0 public | followers_id_seq | 0
If you switch traffic over to PlanetScale in this state, you'll likely encounter errors when inserting new rows:
ERROR: duplicate key value violates unique constraint "XXXX" DETAIL: Key (id)=(ZZZZ) already exists.
Before switching over, you need to progress all of these sequences forward so that the nextval
s produced will be greater than any of the values previously produced on the source Neon database, avoiding constraint violations. There are several approaches you can take for this. A simple way to solve the problem is to first run this query on your source Neon database:
SELECT 'SELECT setval(''' || schemaname || '.' || sequencename || ''', ' || (last_value + 10000) || ');' AS query FROM pg_sequences;
This will generate a sequence of queries that will advance the nextval
by 10,000 for each sequence:
query -------------------------------------------------- SELECT setval('public.users_id_seq', 10104); SELECT setval('public.posts_id_seq', 11416); SELECT setval('public.followers_id_seq', 13013);
You would then execute these on your target PlanetScale database. You need to ensure you advance each sequence far enough forward so that the sequences in the Neon database will not reach these nextval
s before you switch your primary to PlanetScale. For tables that have a high insertion rate, you might need to increase this by a larger value (say, 100,000 or 1,000,000).
6. Cutting over to PlanetScale
Before you cutover, it's good to have confidence that the replication between Neon and PlanetScale is fully caught up. You can do this using Log Sequence Numbers (LSNs). The goal is to see these match up between the source Neon database and the target PlanetScale database exactly. If they don't, it indicates that the PlanetScale database is not fully caught-up with the changes happening on Neon.
You can run this on Neon to see the current LSN:
postgres=> SELECT pg_current_wal_lsn(); pg_current_wal_lsn -------------------- 0/703FE460
Then on PlanetScale, you would run the following query to check for a match:
postgres=> SELECT received_lsn, latest_end_lsn FROM pg_stat_subscription WHERE subname = 'replicate_from_neon'; received_lsn | latest_end_lsn --------------+---------------- 0/703FE460 | 0/703FE460
Once you are comfortable that all your data has successfully copied over and replication is sufficiently caught up, it's time to switch to PlanetScale. In your application code, prepare the cutover by changing the database connection credentials to go to PlanetScale rather than Neon. Then, you can deploy this new version of your application, which will begin using PlanetScale as your primary database.
After doing this, new rows written to PlanetScale will not be reverse-replicated to Neon. Thus, it's important to ensure you are fully ready for the cutover at this point.
Once this is complete, PlanetScale is now your primary database! We recommend you keep your old database around for at least a few days, just in case you discover any data or schemas you forgot to copy over to PlanetScale.
Need help?
Get help from the PlanetScale Support team, or join our GitHub discussion board to see how others are using PlanetScale.