What are the main characteristics of PostgreSQL?

PostgreSQL is an open-source relational database management system with the following key features:

1. Reliability: PostgreSQL ensures data integrity and reliability through various technologies such as Multi-Version Concurrency Control (MVCC) and Write-Ahead Logging (WAL).
2. Scalability: PostgreSQL supports both horizontal and vertical scaling, allowing for increased performance and capacity by adding more server nodes or increasing hardware resources.
3. Compatibility: PostgreSQL adheres to SQL standards and offers numerous extension functionalities and data types, as well as supports access interfaces for multiple programming languages.
4. Integrity: PostgreSQL supports a variety of integrity constraints such as primary keys, foreign keys, uniqueness constraints, and check constraints.
5. Advanced features: PostgreSQL offers a variety of advanced features including complex queries, views, triggers, transactions, stored procedures, and custom functions.
6. Customizability: PostgreSQL allows users to extend and customize the functionality of the database by writing custom plugins and extensions.
7. Security: PostgreSQL offers various security features such as access control, data encryption, and authentication to protect the security of the database.
8. Multiple Version Concurrency Control (MVCC): PostgreSQL employs MVCC to handle concurrent access, allowing multiple users to access the database simultaneously without interfering with each other.

In general, PostgreSQL is a powerful, stable, reliable, scalable, and highly customizable relational database management system.