Last time we demonstrated how to use the ODBC Foreign Data wrapper, this time we'll continue our journey into Foreign Data Wrapper land by demonstrating what I'll call the File FDW family of Foreign Data Wrappers. There is one that usually comes packaged with PostgreSQL 9.1 which is called fdw_file but there are two other experimental ones I find very useful which are
developed by Andrew Dunstan both of which Andrew demoed in PostgreSQL Foreign Data Wrappers and talked
about a little bit Text files from a remote source. As people who have to deal with text data files day in and out, especially ones from mainframes, these satisfy a certain itch.
file_fdw - for querying delimited text files.
file_fixed_length_fdw - this one deals with fixed length data. We discussed methods of importing fixed length data in Import Fixed width data. This is yet another approach but has the benefit that you can also use it to import just a subset of a file.
file_text_array_fdw - this one queries a delimited file as if each delimiete row was a text array. It is ideal for those less than perfect moments when someone gives you a file with a 1000 columns and you don't have patience to look at what the hell those columns mean just yet.
In this article, we'll just cover the file_fdw one, but will follow up in subsequent articles, demonstrating the array and fixed length record ones.