[Illniyar]

This seems like a weird design choice. Why would you need to load a file from the file system as part of a select?

Unless I'm missing some kind of use case this seems like a bad protocol design.

[joelhaasnoot]

Loading a CSV is a common use case. PostgreSQL has a similar \COPY command used for a similar purpose (but that's a client side command not server side as far as I know),

[semiquaver]

psql’s \copy command utilizes the server’s COPY functionality, which absolutely can read and write files on the server or run commands there [1].

  COPY with a file name instructs the PostgreSQL server to directly read from or
  write to a file.  The file must be accessible by the PostgreSQL user (the user
  ID the server runs as) and the name must be specified from the viewpoint of the
  server.

Clients using COPY, including psql’s \copy, often pass STDIN or STDOUT as the “file”, which allows data to be transmitted over the wire rather from the server’s filesystem.

https://www.postgresql.org/docs/11/sql-copy.html

[paulddraper]

https://www.postgresql.org/docs/9.0/sql-copy.html

PostgreSQL COPY can read or write to server files, though it requires superuser permissions.

There is also COPY FROM/TO STDIN/STDOUT, which allows the client to send the files on the same connection.

[quickben]

Performance reasons.