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.
A foreign table created using this wrapper can have the following options:
- filename
Specifies the file to be read. Required. Must be an absolute path name.
- format
Specifies the file's format, the same as COPY's FORMAT option.
- header
Specifies whether the file has a header line, the same as COPY's HEADER option.
- delimiter
Specifies the file's delimiter character, the same as COPY's DELIMITER option.
- quote
Specifies the file's quote character, the same as COPY's QUOTE option.
- escape
Specifies the file's escape character, the same as COPY's ESCAPE option.
- null
Specifies the file's null string, the same as COPY's NULL option.
- encoding
Specifies the file's encoding. the same as COPY's ENCODING option.
COPY's OIDS, FORCE_QUOTE, and FORCE_NOT_NULL options are currently not supported by file_fdw.
These options can only be specified for a foreign table, 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.
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