pg_xlogdump is a new contrib module introduced in PostgreSQL 9.3 by this commit.

Up to Postgres 9.2, the only foreign data wrapper present in core was file_fdw, allowing you to query files as remote tables. This has been corrected with the addition of a second foreign data wrapper called postgres_fdw. This one simply allows to query foreign Postgres servers and fetch results directly on your local server. It has been introduced by this commit.

pageinspect is an extension module of PostgreSQL core allowing to have a look at the contents of relations (index or table) in the database at a low level. In the case of PostgreSQL, tuples of a table are stored in blocks of data whose size can be changed with –with-blocksize at configure step. This module is particularly useful for debugging when implementing a new functionality that changes visibility of data like what could do an autovacuum or map visibility feature, or simply to understand the internals of Postgres without having to read much codea .

Based on my previous experience using custom background workers (new feature of PostgreSQL 9.3), here is more detailed example of bgworker doing a simple “Hello World” in the server logs.

PostgreSQL 9.3 adds a new feature related to monitoring with the commit below.

Prior to PostgreSQL 9.3, there are two levels of locks allowing to control DML operations on a given set of rows for a transaction by using SELECT FOR SHARE and FOR UPDATE. Such locks taken on rows in a transaction block allow blocking INSERT/DELETE/UPDATE on those rows. There is also a protocol between those lock levels. FOR UPDATE is equivalent to an exclusive lock on the row selected, meaning that no other backend can take a FOR UPDATE lock on the same row and waits until the other other transaction finishes. FOR SHARE means that all the other backends can take a FOR SHARE lock on those rows. No FOR UPDATE locks can be taken on rows already locked with FOR SHARE. It is also possible to use the NOWAIT option, making the server return an error if there is a wait situation.

Continuing with the new features planned for PostgreSQL 9.3, here are some explanations about a new COPY mode called FREEZE. This feature has been introduced by this commit.

A new feature ideal for module makers is appearing in Postgres 9.3. Called “background worker processes”, this feature, which is a set of useful APIs, offers the possibility to create and customize worker processes called bgworkers able to run user-specified code directly plugged in the server. This worker is loaded and managed entirely by the server. So such processes can be considered as envelopped in a wrapper on top of the core code as a plug-in.

Prior to PostgreSQL 9.3, trying to execute a DML on a view results in an error. The view is not able to execute directly a query to its parent table. For example, you can see this kind of behavior in 9.2.

Since PostgreSQL 9.1, it is possible to switch a standby server to follow another server that has been freshly promoted after the master node of a cluster is out due to a failure (disaster or another). In this example, a master and two slaves are running on the same machine. The master running with port 5432 fails, Slave 1 is promoted as the new master: