Re: [GSOC] questions about idea "rewrite pg_dump as library"

I was just thinking of moving the queries the pg_dump currently

uses into UDF-s, which do _not_ use catalog cache, but will use
the same SQL to query catalogs as pg_dump currently does
using whatever snapshot mode is currently set .

the pg_dump will need to still have the same queries for older
versions of postgresql but for new versions pg_dump  can become
catalog-agnostic.

and I think that we can retire pg_dump support for older
postgresql versions the same way we drop support for
older versions of postgresql itself. 

main things I see would be

 * get_list_of_objects(object_type, pattern or namelist)
 * get_sql_def_for_object(object_type, object_name)
 * sort_by_dependency(list of [obj_type, obj_name])

from this you could easily construct most uses, especially if
sort_by_dependency(list of [obj_type, obj_name])
would be smart enough to break circular dependencies, like
turning to tables with mutual FK-s into tabledefs without
FKs + separate constraints.