I've seen this idea pop up over the years, and it's still a good one. Rather than invent new flags, I think a better approach would be to convince pg_dump to dump a view, such that table foo has a view fooslice to limit / filter the output. Then we can simply do:
pg_dump -t foo=view:fooslice and under the hood pg_dump would do COPY (SELECT * FROM fooslice) TO ... rather than COPY foo TO ... While we could make the view mapping into a separate filtering file as you suggest, that's more complexity and also a little more dangerous in an action-at-a-distance way, so I'd rather have people be very specific in the mapping on the command line. I could swear I made a POC years ago for something like this, but it's long gone. If I get some time, I'll give it a fresh attempt. Cheers, Greg -- Crunchy Data - https://www.crunchydata.com Enterprise Postgres Software Products & Tech Support
