PostgreSQL Logical Replication Guide

Step-by-Step Tutorial: Setting Up PostgreSQL Logical Replication

1. Understand Logical Replication: Logical replication in PostgreSQL allows replicating individual tables or subsets of tables by sending actual SQL commands instead of physical data. It provides more flexibility and control compared to physical replication.

2. Set Up Environment:

   • Use the initdb command to create two PostgreSQL database clusters, one for the publisher and one for the subscriber.
   • Modify the postgresql.conf file for both instances by setting the wal_level parameter to logical and adjusting the port numbers.

3. Start PostgreSQL Instances:

   • Start the publisher instance on port 5433 using pg_ctl -D [publisher_directory] start.
   • Start the subscriber instance on port 5434 similarly.

4. Create Schema and Data:

   • Connect to the instances using psql specifying the port and default database.
   • Create a sample table on the publisher with some data.
   • Use pg_dump to extract the schema and data from the publisher and apply it to the subscriber using psql.

5. Create Publication and Subscription:

   • Create a publication for the desired table(s) on the publisher using CREATE PUBLICATION.
   • Create a subscription on the subscriber to receive changes from the publication using CREATE SUBSCRIPTION.

6. Verify Replication:

   • Check if the initial data is replicated to the subscriber.
   • Insert, update, delete, or truncate data on the publisher and verify if these changes are replicated to the subscriber.

7. Monitor Replication:

   • Use pg_stat_replication table to monitor replication lag, bytes processed, and other vital information.
   • Ensure that the replication process is working correctly by monitoring the lag and replication stages.

8. Understand Limitations:

   • Note that schema changes need to be synchronized manually between the publisher and subscriber.
   • Sequence data is not replicated, and manual adjustments may be required for failover scenarios.

9. Explore Use Cases:

   • Understand the benefits of logical replication in scenarios requiring flexibility, identical schemas, and cross-platform replication.
   • Utilize logical replication for consolidating data from multiple servers, fine-grained control over replication, and optimizing performance.

10. Optimize Performance:

    • Utilize logical replication for better performance in scenarios where network bandwidth is limited or complex operations like vacuum and cluster need to be optimized.

By following these steps, you can effectively set up and utilize PostgreSQL logical replication for your database management needs.