Hello World Tutorial

Mon, 01 Jan 0001 00:00:00 +0000

This tutorial walks through the core operations of pg_mooncake: creating a regular PostgreSQL rowstore table, creating a real-time columnstore mirror (USING mooncake), running transactional INSERT, UPDATE, and DELETE statements, testing rollback semantics, and joining columnstore and rowstore tables.

1. Enable the Extension

Connect to your PostgreSQL database and ensure pg_mooncake (along with pg_duckdb) is enabled:

CREATE EXTENSION IF NOT EXISTS pg_mooncake CASCADE;

2. Create a Rowstore Table & Columnstore Mirror

First, create a standard PostgreSQL heap table (user_activity) for your transactional writes, then call mooncake.create_table to create its real-time columnstore mirror (user_activity_columnstore):

Known Limitations

Mon, 01 Jan 0001 00:00:00 +0000

Before deploying pg_mooncake (v0.3.0) in production, review the following architectural constraints and known limitations.

1. Read-Only Columnstore Mirror Tables

Tables created with CALL mooncake.create_table(dst, src) use the USING mooncake table access method and are read-only replicas.

Direct INSERT, UPDATE, DELETE, or COPY statements targeting the USING mooncake table are rejected by PostgreSQL (ERROR:cannot modify table "..." because it uses the mooncake access method).
Always execute DML operations against the source rowstore table (src); changes replicate automatically via moonlink.

2. Primary Keys & `REPLICA IDENTITY FULL`

To replicate UPDATE and DELETE operations accurately over PostgreSQL logical replication, the source table must provide complete old-row identification in the WAL stream: