F.14. file_fdw

The file_fdw module provides the foreign-data wrapper file_fdw, which can be used to access data files in the server's file system. Data files must be in a format that can be read by COPY FROM; see COPY for details. Access to such data files is currently read-only.

A foreign table created using this wrapper can have the following options:

Note that while COPY allows options such as OIDS and HEADER to be specified without a corresponding value, the foreign data wrapper syntax requires a value to be present in all cases. To activate COPY options normally supplied without a value, you can instead pass the value TRUE.

A column of a foreign table created using this wrapper can have the following options:

COPY's OIDS and FORCE_QUOTE options are currently not supported by file_fdw.

These options can only be specified for a foreign table or its columns, not in the options of the file_fdw foreign-data wrapper, nor in the options of a server or user mapping using the wrapper.

Changing table-level options requires superuser privileges, for security reasons: only a superuser should be able to determine which file is read. In principle non-superusers could be allowed to change the other options, but that's not supported at present.

For a foreign table using file_fdw, EXPLAIN shows the name of the file to be read. Unless COSTS OFF is specified, the file size (in bytes) is shown as well.

CREATE EXTENSION file_fdw;

CREATE SERVER pglog FOREIGN DATA WRAPPER file_fdw;

CREATE FOREIGN TABLE pglog (
  log_time timestamp(3) with time zone,
  user_name text,
  database_name text,
  process_id integer,
  connection_from text,
  session_id text,
  session_line_num bigint,
  command_tag text,
  session_start_time timestamp with time zone,
  virtual_transaction_id text,
  transaction_id bigint,
  error_severity text,
  sql_state_code text,
  message text,
  detail text,
  hint text,
  internal_query text,
  internal_query_pos integer,
  context text,
  query text,
  query_pos integer,
  location text,
  application_name text
) SERVER pglog
OPTIONS ( filename '/home/josh/9.1/data/pg_log/pglog.csv', format 'csv' );