PGHOSThostname

PGHOSThostname is not an official PostgreSQL parameter. In practice, the term is sometimes used informally to refer to the hostname component that the PostgreSQL client environment variable PGHOST targets when establishing a connection. The article below explains the standard behavior of PGHOST and how a hostname value influences connections.

PGHOST is an environment variable used by PostgreSQL client libraries (libpq) to specify where to connect. When PGHOST is unset or empty, the client typically tries to connect using a local Unix-domain socket. When PGHOST is set to a hostname or IP address, the client makes a TCP/IP connection to that host on the port defined by PGPORT (default 5432). Some values can also point to a directory path containing Unix sockets; in that case, the client will use the sockets in that directory instead of a network connection.

Hostname values can be standard domain names (for example, db.example.com) or special values such as localhost. Using localhost resolves to the local machine and may choose between a TCP/IP loopback connection or a local socket, depending on configuration. The distinction between using 127.0.0.1 (IPv4) and ::1 (IPv6) can affect routing and authentication behavior.

PGHOST is commonly used alongside other connection parameters (PGPORT, PGDATABASE, PGUSER, PGPASSWORD, and optionally a pg_service file). In many environments, connections are defined via a service in pg_service.conf, which groups host, port, and database settings. If you encounter PGHOSThostname, it is likely a placeholder or documentation shorthand for the hostname value associated with PGHOST rather than a separate, official PostgreSQL variable.