The Internals of PostgreSQL Chapter 2 : Exploring the Process and Memory Architecture of PostgreSQL
Tags: postgres, postgressql, apacheage
Published: 2023-06-27 12:25:22



PostgreSQL, known as Postgres, is a vigorous and feature-rich open-source relational database system. Its design plays a pivotal part in guaranteeing proficient query execution, execution of concurrent processes, and effecient memory allocation. In this blog, I will give a brief summary from the book  "[The Internals of PostgreSQL](https://www.interdb.jp/pg/pgsql02.html)" chapter 2 by Hironobu SUZUKI about the process architecture and memory architecture of PostgreSQL, particularly examining shared and local memory. 

##Process Architecture:

The *postmaster process* lies at the core of PostgreSQL's process architecture. The parent process supervises the management of all other processes that are executed within the system. When there is a client connection request, the postmaster initiates a dedicated backend process to carry out the execution of that specific connection. Such kind of multi-process approach empowers PostgreSQL to handle the execution of concurrent database operations efficiently.

The role of backend processes is very important in executing client queries and handling database connections. There is a separate backend process for each client connection, which is responsible for query execution and communication with the client. Moreover, shared buffer processes help cache the data pages that are frequently accessed in the shared buffer pool, this is the part of memory that is accessible to all the backend processes. The shared buffer pool plays a vital role in improving performance by diminishing disk I/O operations. 


 
##Memory Architecture:

Memory architecture in PostgreSQL can be classified into two broad categories:
Local memory area 
Shared memory area 

###Shared Memory Area:

One of the important aspects of PostgreSQL's memory architecture is share memory that provides efficient interprocess communication and sharing of data among different components. Shared memory is prominently use as the shared buffer pool. The shared buffer pool plays a vital role in improving performance by diminishing disk I/O operations. The backend processes can easily access and modify the data within the shared buffer pool, which results in speedy execution improving the performance and reducing the latency.

###Local Memory area:

Each backend process in PostgreSQL has its own dedicated local memory. This local memory is allocated to each process and is utilized for managing the temporary data structures when query execution occurs. This stores the instant query results, offering sorting operations and taking care of other memory-intensive tasks. Local memory offers segregation and guarantees that processes can work freely without depending on and interfering with each other's memory space.
 
##Conclusion:

PostgreSQL's engineering is planned to execute concurrent database operations proficiently. The process architecture, with the postmaster and backend processes, empowers concurrent query execution and successful client communication. In the mean time, the memory architecture optimizes query execution and data caching.

Shared memory, such as the shared buffer pool, allows backend processes to get to as often as possible gotten to data pages from memory, diminishing disk I/O operations and progressing general execution. Local memory, on the other hand, gives each backend process with its own memory context, guaranteeing segregation and proficient management of temporary data structures amid query execution.