Hi čt 18. 6. 2020 v 0:47 odesílatel David G. Johnston < david.g.johns...@gmail.com> napsal:
> This is a follow-up to Bug # 16492 which also links to a thread sent to > -hackers back in 2018. > > I'm firmly of the belief that the existing behavior of DROP relation IF > EXISTS is flawed - it should not be an error if there is a namespace > collision but the relkind of the existing relation doesn't match the > relkind set by the DROP command. > > Since our documentation fails to elaborate on any additional behavior, and > uses the relkind in the description, our users (few as they may be) are > rightly calling this a bug. I loosely believe that any behavior change in > this area should not be back-patched thus for released versions this is a > documentation bug. I have attached a patch to fix that bug. > > In putting together the patch I noticed that the existing drop_if_exists > regression tests exercise the DROP DOMAIN command. Out of curiosity I > included that in my namespace testing and discovered that DROP DOMAIN > thinks of itself as being a relation for purposes of IF EXISTS but DROP > TABLE does not. I modified both DROP DOMAIN and the Glossary in response > to this finding - though I suspect to find disagreement with my choice. I > looked at pg_class for some guidance but a quick search for RELKIND_ > (DOMAIN) and finding nothing decided I didn't know enough and figured to > punt on any further exploration of this inconsistency. > > The documentation and tests need to go in and be back-patched. After that > happens I'll see whether and/or how to go about trying to get my PoV on the > behavioral change committed. > I am reading this patch. I don't think so text for domains and types are correct (or minimally it is little bit messy) + This parameter instructs <productname>PostgreSQL</productname> to search + for the first instance of any relation with the provided name. + If no relations are found a notice is issued and the command ends. + If a relation is found then one of two things will happen: + if the relation is an domain it is dropped, otherwise the command fails. "If no relations are found ...". This case is a little bit more complex - domains are not subset of relations. But relations (in Postgres) extends types. So in this case maybe modified text can be better + This parameter instructs <productname>PostgreSQL</productname> to search + for the first instance of any domain with the provided name in pg_type catalog. + If no type is found a notice is issued and the command ends. + If a type is found then one of two things will happen: + if the type is a domain it is dropped, otherwise the command fails. Postgres knows + base types, composite types, relation related types and domain types. Regards Pavel > > David J. > >
