Database Reference
In-Depth Information
One of the key features of Oracle since Oracle 7 has been "snapshot isolation", where
readers don't block writers, and writers don't block readers. You may be surprised to learn
that PostgreSQL was the first database to be designed with this feature, and offers a full and
complete implementation. PostgreSQL names this Multi-Version Concurrency Control (MVCC),
and we will discuss this in more detail later in this topic.
PostgreSQL is a general-purpose database management system. You define the database that
you would like to manage with it. PostgreSQL offers you many ways to work. You can use a
"normalized database model", you can utilize extensions such as arrays and record subtypes,
or you can use a fully dynamic schema using an extension named hstore. PostgreSQL also
allows you to create your own server-side functions in one of a dozen different languages.
PostgreSQL is highly extensible, so you can add your own datatypes, operators, index types,
and functional languages. For example, you can override different parts of the system using
plugins to alter the execution of commands or add a new optimizer.
All of these features offer a huge range of implementation options to software architects.
There are many ways out of trouble when building applications and maintaining them over
long periods of time. Regrettably, we simply don't have space in this topic for all of the cool
features for developers—this topic is about administration, maintenance, and backup.
In the early days, when PostgreSQL was still a research database, the focus was solely on cool
new features. Over the last 15 years, enormous amounts of code have been rewritten and
improved, giving us one of the most stable, large, software servers available for operational use.
You may also read that PostgreSQL was, or is, slower than My Favorite DBMS, whichever
one that is. It's been a personal mission of mine over the last six years to improve server
performance and the team have been successful in making the server highly performant and
very scalable. That gives PostgreSQL enormous headroom for growth.
Who is using PostgreSQL? Prominent users include Apple, BASF, Genentech, IMDB.com,
Skype, NTT, Yahoo, and The National Weather Service. PostgreSQL receives well in excess of
1 million downloads per year, according to data submitted to the European Commission, who
concluded "...PostgreSQL, is considered by many database users to be a credible alternative...
We need to mention one last thing. When PostgreSQL was first developed, it was named
Postgres, and so many aspects of the project still refer to the word "postgres". For example,
the default database is named postgres, and the software is frequently installed using the
postgres userid. As a result, people shorten the name PostgreSQL to simply Postgres, and in
many cases people use the two names interchangeably.
PostgreSQL is pronounced as "post-grez-q-l". Postgres is pronounced as "post-grez".
Some people get confused, and refer to "Postgre", which is hard to say, and likely to confuse
people. Two names are enough, so please don't use a third name!
