PostgreSQL Concepts

External

• https://www.postgresql.org/docs/14/glossary.html

Internal

• PostgreSQL

Connection Types

Local Socket

This is the default type of connection, then the psql client is collocated with the database.

TCP

The default port is 5432.

Cluster

A collection of databases and global SQL objects, and their common static and dynamic metadata. A clusters is also referred to as instance. There is no relationship within the PostgreSQL cluster and the SQL term "CLUSTER".

Cluster Operations

• Create a database cluster

Instance

An instance is a group of backend and auxiliary processes that communicate using a common shared memory area. There is one postmaster process that manages the instance. One instance manages exactly one database cluster with all its databases. Many instances can run on the same server machine as long as the TCP ports do not conflict. The instance handles all key features of a RDBMS: read and write access to files and shared memory, enforcement of ACID properties, connections to clients, privilege verification, crash recovery, replication, etc.

Database

https://www.postgresql.org/docs/14/manage-ag-overview.html

A database is a named collection of local SQL objects. A local SQL object is any object that can be created with an SQL CREATE command.

A PostgresSQL usually comes with 4 pre-existing databases (postgres, admin, template0, template1). "postgres" is fit for general use and it should be used by default.

Database Name Case Sensitivity

Verify this:

It seems that the database name is case sensitive, even if a database is created with "CREATE DATABASE TEST_DB", the database name becomes "test_db", and this is what it should be used in the connect URL. "jdbc:postgres://localhost/test_db" will work, but "jdbc:postgres://localhost/TEST_DB" won't.

Schema

Each database has by default a public schema.

Authentication

User

Users are shared across databases.

The "user" concept is equivalent with the "role" concept. They mean the same thing.

User Operations

Master User

An administrative user that exists when the RDBMS instance is created and that has privileges to create other database and other users. It is used to bootstrap the administration of the RDBMS instance, by defining all users, objects, and permissions in the databases of your DB instance. Master Username must start with a letter. The RDS documentation refers to it as "Master username".

Role

The "role" concept is equivalent with the "user" concept. They mean the same thing.

Role Attributes

A specific role may:

• be a superuser
• create another role
• create a database

Data Types

Identity

• http://www.postgresqltutorial.com/postgresql-identity-column/
• http://www.postgresqltutorial.com/postgresql-serial/

Numeric Types

• https://www.postgresql.org/docs/9.1/static/datatype-numeric.html

SMALLINT

2 byte integer.

INT

4 byte integer. This is a typical choice for integers.

BIGINT

8 byte integer.

BIGSERIAL

TODO

Environment Variables

PGDATA

Set it after installation, see:

PostgreSQL Installation on Mac