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:

A foreign-data wrapper (FWD) in a Postgres server allows to fetch data from an foreign entity or a foreign server. In this case, the Postgres planner and executer have the notion of what is called a foreign scan, which can be called using customized routines and fetch data that is not directly stored inside the Postgres server itself.

pg_buffercache is a PostgreSQL contrib module allowing to get an instant relation-based view of the shared buffer usage by querying the wanted server.

One of the new features introduced by PostgreSQL 9.2 is called range types, which is, as you could easily guess based on this feature name, the possibility to use a range of values directly as a table column.

hstore is a PostgreSQL contrib module in core code for a pretty long time. Its code is located in contrib/hstore in source folder. It is particularly useful to store sets of key/value in a single table column.