Re: PostgreSql Doubt

I have a data source for example in file format(xml,csv ..etc) , i want to use postgresql engine to query select,update,insert using foreign data wrappers(fdw).

updating/inserting into a CSV, XML, or whatever flat file will be very painful, it will require copying the whole file with the new/changed record in place.

I would recommend instead importing your XML/CSV/etc data into SQL table(s), do your data operations there, then export the results back as XML or whatever if you really need it that way.

-- 
john r pierce, recycling bits in santa cruz