Have you ever heard about mpd? It is an open source music player that works as a server-side application playing music, as well as in charge of managing the database of songs, playlists. It is as well able to do far more fancy stuff… Either way, mpd has a set of client APIs making possible to control the operations on server called libmpdclient, library being used in many client applications available in the wild, able to interact with a remote mpd instance. The most used being surely mpc, ncmpc and gmpc. There are as well more fancy client interfaces like for example libmpdee.el, an elisp module for emacs. Now, PostgreSQL has always lacked a dedicated client interface, that’s where [pgmpc] (https://github.com/michaelpq/pg_plugins/tree/master/pgmpc) satisfies this need by providing a set of SQL functions able to interact with an instance of mpd, so you can control your music player directly with Postgres.

Behind this eye-catching title is an [extension] (https://www.postgresql.org/docs/devel/static/extend-extensions.html) called blackhole that I implemented yesterday, tired of needing to always structure a fresh extension when needing one (well copying one from Postgres contrib/ would be fine as well). Similarly to [blackhole_fdw] (https://bitbucket.org/adunstan/blackhole_fdw/src) that is aimed to be an extension for a foreign-data wrapper, blackhole is an extension wanted as minimalistic as possible that can be used as a base template to develop a Postgres extension in C.

Logical decoding is a superset of the existing standby protocol. Hence after decoding changes from WAL an output plugin can shape it in any kind of ways, making for example possible to have a plugin that does the exact revert operation of the decoding portion a PostgreSQL server instancedid by reproducing similar WAL records that could be replayed similarly to a standby. Not sure if this would be actually useful, but well that’s possible…

Introduced in PostgreSQL 9.4, [pg_recvlogical] (https://www.postgresql.org/docs/devel/static/app-pgrecvlogical.html) has the ability to control the creation of logical replication slots from which logical changes can be streamed. Note that in the case this is a mandatory condition when using [logical decoding] (https://www.postgresql.org/docs/devel/static/logicaldecoding.html). [pg_receivexlog] (https://www.postgresql.org/docs/devel/static/app-pgreceivexlog.html) does not have in 9.4 any control on the physical replication slots it may stream from (to ensure that the WAL segment files this utility is looking for are still retained on the server side). This feature has been added for 9.5 with the following commit:

SKIP LOCKED is a new feature associated with [row-level locking] (https://www.postgresql.org/docs/devel/static/explicit-locking.html#LOCKING-ROWS) that has been newly-introduced in PostgreSQL 9.5 by this commit:

Row-level security is a new feature of PostgreSQL 9.5 that has been introduced by this commit:

The following simple commit has improved the verbose logs of [pg_dump] (https://www.postgresql.org/docs/devel/static/app-pgdump.html) (the ones that can be invocated with option -v and that are useful to keep a log trace when using cron jobs kicking pg_dump), by making the schema names of the relations dumped show up as well:

Postgres 9.5 will come up with an additional logging option making possible to log replication commands that are being received by a node. It has been introduced by this commit.

Customizing the shape of logs written by a PostgreSQL server is possible using a hook present in core code invocated before sending anything to the server logs.

Introduced in PostgreSQL 9.1, an [unlogged table] (https://www.postgresql.org/docs/devel/static/sql-createtable.html) offers the possibility to create a table whose definition is permanent on server, but its content is not WAL-logged making it not crash-safe, with data that cannot be accessed on a read-only stannby continuously replaying WAL at recovery. Postgres 9.5 offers an improvement in this area with the possibility to switch the persistency of an unlogged to permanent and vice-versa: