PostgreSQL extendability: Origins and new horizons

Postgres was initially designed to support access methods extendability. Well known citation about access method in Postgres claims: "It is imperative that a user be able to construct new access methods to provide efficient access to instances of nontraditional base types" Michael Stonebraker, Jeff Anton, Michael Hirohama. Extendability in POSTGRES, IEEE Data Eng. Bull. 10 (2) pp.16-23, 1987

Initially, heap was just one for access methods. So, extendability of access methods would also mean pluggable storage engines in modern terms. For now, only index access methods are defined in pg_am table of system catalog. Those index access methods also have well-defined interface. Therefore in order to meet initial design PostgreSQL need to support two features:

• Pluggable index access methods, i.e. ability to implement new index types by adding new tuples to pg_am;
• Pluggable storage engines, i.e. ability to implement completely different storages for tables without traditional heap.

Besides mechanical work like "CREATE ACCESS METHOD" command, extensible index access methods needs to be WAL-logged. For now, community doesn't want extensions to define their own WAL-records, because there is a chance to break both recovery and replication, which is not acceptable. Another approach is to define generic WAL-records, that specify a difference between pages in generalized way.

There are only few DBMS which support pluggable storage engines now. MySQL is the most common example here. However, dealing with different storage engines in MySQL is like dealing with different DBMS. This is not the way PostgreSQL should go from our view.

However, now PostgreSQL users realize benefits from other storages. Ideas of columnar storages and in-memory storages for PostgreSQL are very popular. Simultaneously, technical possibilities to implement them are growing. FDW and custom nodes are arrived. Generic WAL and extensible index access methods are pending for 9.6. Much work in the direction of pluggable storage engines is already done even if it had different aims.

It's time for PostgreSQL core developers to think about native support of pluggable storages without kludges. Finally, we should get "CREATE STORAGE ENGINE name ..." command as legal extendability mechanism.

In this talk we will show current state on pluggable index access method and design of pluggable storage engines.

The base version of DBMS PostgreSQL can register events bellow: - connect and disconnect - denial of access with date, time and user's name.

Requirements guidelines for audit subsystem is much wider possibilities basic version of database PostgreSQL.

The RusBITech company holds the necessary improvements PostgreSQL database to enhance it's functionality.

A result of improvements audit subsystem of PostgreSQL database as part of the operating system «Astra Linux Special Edition» further enables registration:

• The creation and destruction of database objects;
• Changes to the rules of access control;
• Both failures and successful attempts to access the database objects;
• Changes to the powers and status of subjects access objects access.

For all events are specified: - date and time; - The user performing the action of the registrant; - The object on which the action is carried out; - Type of event; - The result of the operation.

Audit subsystem of modified PostgreSQL is integrated into a centralized audit system OS «Astra Linux Special Edition». Provided the rules setting without stopping the logging (restarting) database.

My Five Slides About Postgres

My experience of working with PostgreSQL has provided clear understanding of its main advantages, making us choose and recommend choosing it.
1. Beginning
2. Documentation
3. Community
4.1 Transactional DDL
4.2 WAL and True Physical Replication
4.3 Transactional Snapshot and True Logical Replication and PGQ
4.4 Exciting extensibility
5. Success