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.
+1
This is an excellent idea. This would allow doing all kinds of crazy things outside of the scope of pg_dump.
2 years ago I was working on a system to version control the schema, inside the database.
Don't know if it's a good idea or not, but one thing which bugged me a lot was the lack of pg_get_[object type]def(oid) functions for all different object types.
It also turned out to be quite complicated to do the pg_depend topological sort yourself. I managed eventually, but it was running to slow because I had to pass the entire content of pg_depend to a plperl function I wrote.
With this in place I would be motivated enough to resume my old project, which is still online at https://github.com/gluefinance/pov if anyone is interested.
Is it really necessary to write all the missing pg_get_[object type]def(oid) functions in C? I think it would be quite easy to put them together using pure SQL, you wouldn't even need PL/pgSQL.
This old view I once wrote manage to produce working create and drop statements for most object types using SQL only:
It would also be nice with functions which returned the proper command to DROP an object. I need it in this project in order to do schema modifications where objects have to be dropped/recreated in a particular order to not break dependencies. Perhaps there are other use cases out there.
