PostgreSQL is a client/server relational database management system (RDMS). PostgreSQL also supports a wide range of extensions, such as the Citus extension in the Azure Cosmos DB for PostgreSQL option. After an extension is loaded into the database, it functions like any built-in feature.
PostgreSQL also has its own query language called pgsql. In addition, PostgreSQL supports procedural languages such as Ruby on Rails.
Client/server architecture
PostgreSQL is based on a client/server architecture. The server stores, manages, and returns data to client programs. Client programs request data using pgSQL, or one of the procedural languages that PostgreSQL supports, such as PL/pgSQL.
A PostgreSQL session consists of three parts:
- The postmaster
- The client application
- The server
Postmaster
The Postmaster is the supervisory daemon process that manages a PostgreSQL server. The postmaster daemon manages communication among the various server processes including initializing the server, shutting down the server, handling connection requests, and performing other background processes. In Azure Database for PostgreSQL, you don’t have access to the file system, or to the Postmaster process.
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