PostgreSQL: Key Features and Use in Web Development

Functions are server-side routines executed by the PostgreSQL server. Although they can be written in pure SQL, implementing additional logic—such as conditional branching and loops—goes beyond the scope of SQL itself and requires procedural languages such as PL/pgSQL.

Functions can be written in several supported procedural languages, including PL/pgSQL, PL/Python, and PL/Perl. PostgreSQL supports functions that return a set of records, which can then be used in the same way as the result of a regular query. Functions execute with either SECURITY DEFINER or SECURITY INVOKER privileges. Functions and stored procedures are different database objects.

Triggers in PostgreSQL invoke trigger functions in response to DML events. For example, an INSERT operation can invoke a trigger that checks whether the inserted row meets certain conditions. Trigger functions can be written in several procedural languages. Triggers are associated with tables. Multiple triggers are executed in alphabetical order.

The rule system allows SQL statements to be rewritten before execution.

The main difference from the trigger mechanism is that rules are fired during the query parsing phase, before the query planner generates an execution plan. Rules allow you to override the system’s behavior when executing an SQL operation on a table.

PostgreSQL uses Multiversion Concurrency Control (MVCC) that allows multiple users to make changes to the database at the same time. This virtually removes the need for read locks and ensures ACID compliance.

PostgreSQL can be extended in almost any way to meet unique requirements. User-defined casts, data types, functions (including aggregate functions), domains (user-defined types with built-in constraints), indexes, operators (including overrides of preexisting ones), and procedural languages can all be added.

Inheritance in PostgreSQL is implemented at the table level.

Tables can inherit columns and constraints from other (parent) tables. In this case, data added to the derived table will automatically be included (unless specified otherwise) in queries against the parent table.

In the development of simple websites, PostgreSQL is used less frequently than MySQL and MariaDB — this pair remains the most widely used DBMSs for CMS-based websites. However, in the development of complex websites and web applications, PostgreSQL is widely used for complex web applications that require advanced database features. Most frameworks (such as Ruby on Rails, Symfony, and Django) support the use of PostgreSQL in web application development.

In the development of content-driven websites, MySQL and MariaDB remain the most widely used database management systems because many popular CMS platforms are built around them. However, PostgreSQL is often preferred for complex web applications due to its advanced features, extensibility, and standards compliance. Most modern web frameworks, including Ruby on Rails, Symfony, and Django, provide excellent support for PostgreSQL.

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