DOKK / manpages / debian 12 / postgresql-client-common / pg_wrapper.1.en
PG_WRAPPER(1) Debian PostgreSQL infrastructure PG_WRAPPER(1)

pg_wrapper - wrapper for PostgreSQL client commands

client-program [--cluster version/cluster] [...]

(client-program: psql, createdb, dropuser, and all other client programs installed in /usr/lib/postgresql/version/bin).

This program is run only as a link to names which correspond to PostgreSQL programs in /usr/lib/postgresql/version/bin. It determines the configured cluster and database for the user and calls the appropriate version of the desired program to connect to that cluster and database, supplying any specified options to that command.

The target cluster is selected by the following means, in descending order of precedence:

  • explicit specification with the --host option
  • explicit specification with the --cluster option
  • if the PGHOST environment variable is set, no further cluster selection is performed. The default PostgreSQL version and port number (from the command line, the environment variable PGPORT, or default 5432) will be used.
  • explicit specification with the PGCLUSTER environment variable
  • if a port is given (either via -p, --port, or PGPORT), and no host is given, the local cluster matching that port number is used
  • matching entry in ~/.postgresqlrc (see postgresqlrc(5)), if that file exists
  • matching entry in /etc/postgresql-common/user_clusters (see user_clusters(5)), if that file exists
  • If only one cluster exists on the local system, that one will be selected.
  • If several clusters exist on the local system, the one listening on the default port 5432 will be selected.

If none of these rules match, pg_wrapper does not set any environment variables and the program called will likely error out with a message like "could not connect to server: Connection refused".

For psql, pg_archivecleanup, and pg_isready, pg_wrapper will always use the binary from the newest PostgreSQL version installed, as these are downwards compatible. If the cluster version is older than 9.2, the newest considered binary version is 14.

Note that pg_wrapper needs to be able to read the server config to get the port number to connect to. If a non-standard port is configured in a place that pg_wrapper cannot read, connecting will fail. This particularly holds if the port was configured via ALTER SYSTEM in postgresql.auto.conf and pg_wrapper is invoked as any user other than postgres and root.

cluster is either the name of a cluster on the local system, or takes the form host:port for a remote cluster. If port is left empty (i. e. you just specify host:), it defaults to 5432.

If $PGCLUSTER is set, its value (of the form version/cluster) specifies the desired cluster, similar to the --cluster option. However, if --cluster is specified, it overrides the value of $PGCLUSTER.
This specifies an alternative base directory for cluster configurations. This is usually /etc/postgresql/, but for testing/development purposes you can change this to point to e. g. your home directory, so that you can use the postgresql-common tools without root privileges.
This is the location of PostgreSQL's and postgresql-common's global configuration (e. g. pg_service.conf, user_clusters(5)). The default is /etc/postgresql-common/.

/etc/postgresql-common/user_clusters
stores the default cluster and database for users and groups as set by the administrators.
$HOME/.postgresqlrc
stores defaults set by the user himself.

user_clusters(5), postgresqlrc(5)

Martin Pitt <mpitt@debian.org>

2023-03-14 Debian