Introduction

License

This extension and its documentation are released under the GNU General Public License (GPL).

E-Maj’s objectives

E-Maj is the French acronym for “Enregistrement des Mises À Jour”, which translates to “Updates Recording”.

It serves two primary purposes:

  • Audit Trail: E-Maj can trace updates performed by application programs on table content. Viewing these recorded updates addresses the need for auditing database changes.

  • Logical Restoration: Using these recorded updates, E-Maj can logically restore sets of tables to predefined states, without requiring a full restore of the PostgreSQL instance (cluster) or reloading the entire content of the affected tables.

In other words, E-Maj is a PostgreSQL extension that enables fine-grained write logging and time travel on subsets of the database.

It provides an efficient solution to:

  • define savepoints at precise times for a set of tables,

  • restore, if needed, this table set to a stable state without stopping the instance,

  • manage multiple savepoints, each usable at any time as a restore point.

In a production environment, E-Maj simplifies the technical architecture by offering a smooth and efficient alternative to time-consuming and disk-intensive intermediate saves (e.g., pg_dump, mirror disks, etc.). It also aids debugging by enabling precise analysis of how suspicious programs update application tables.

In a test environment, E-Maj streamlines operations by allowing easy restoration of database subsets to predefined stable states, so that tests can be replayed as many times as needed.

Main components

E-Maj consists of several components:

  • a PostgreSQL extension object created in each database, named emaj and containing tables, functions, sequences, etc.,

  • a set of command-line external clients,

  • a web GUI, Emaj_web.

The external clients and the GUI call the functions of the emaj extension.

_images/components.png

All these components are described in the documentation.