To connect RisingWave to a self-hosted PostgreSQL database for Change Data Capture (CDC), you need to configure your database to support logical replication.

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1. Set wal_level to logical

In your postgresql.conf file or via a SQL client, set the wal_level parameter to logical. 
ALTER SYSTEM SET wal_level = logical;
This change requires a restart of your PostgreSQL server to take effect.
If you plan to create multiple CDC sources, ensure the max_wal_senders parameter in your postgresql.conf is greater than or equal to the number of sources you intend to create. The default value is typically 10.

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2. Create a dedicated replication user

Create a dedicated PostgreSQL user for replication. This user needs the REPLICATION and LOGIN attributes. 
-- Create a new user with a secure password
CREATE USER <user_name> WITH REPLICATION LOGIN PASSWORD '<your_password>';

-- Or, modify an existing user
ALTER USER <user_name> WITH REPLICATION LOGIN;

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3. Grant required privileges

Grant the user the necessary privileges on the database and schemas you want to capture changes from. 
-- Grant connection access to the database
GRANT CONNECT ON DATABASE <database_name> TO <user_name>;

-- If RisingWave needs to create the publication, grant CREATE privilege
GRANT CREATE ON DATABASE <database_name> TO <user_name>;

-- Grant usage on the schema
GRANT USAGE ON SCHEMA <schema_name> TO <user_name>;

-- Grant select on all tables in the schema
GRANT SELECT ON ALL TABLES IN SCHEMA <schema_name> TO <user_name>;
-- To grant access to future tables in the schema automatically:
ALTER DEFAULT PRIVILEGES IN SCHEMA <schema_name> GRANT SELECT ON TABLES TO <user_name>;

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Next step

Now that your database is configured, you can proceed to connect RisingWave. ➡️ Connect to PostgreSQL CDC
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