01pg-PostgreSQL Basics – Overview

PostgreSQL Overview.

In PostgreSQL, data is stored in pages or blocks within the file system on attached storage.


  • Data is Stored in 1 or More 1 GB files.
  • Data files are read / written to 8KB pages.
  • Page a.k.a Block or Blk

PostgreSQL Server Process:

Postgres server process is the parent of all Process related to PG DB cluster and it implements the TCP listener process and by default it accepts the connection on port number 5432 when a client connects to the Postgres process, and it forks new backend process which is seen in the below image.

Each of the clients connected to the backend process interacts with the instance of the associated background process and it depends on the resource available on the server and it’s controlled by the parameter max_connections.


Query Processing:

A query received by the backend process goes through five stages of processing. At each stage, certain actions are taken, and an output is generated, which is fed as input into the next stage. The client establishes a connection with the backend process to create a parser process.


Statistics Collector:

Collects the Stats of the Table and provides the info to the planner and the executor executes the task based on the stats available.


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