On Wed, 2006-05-24 at 09:40 -0400, Tom Lane wrote: > Simon Riggs <[EMAIL PROTECTED]> writes: > > On Wed, 2006-05-24 at 11:17 +0300, Hannu Krosing wrote: > >> Why "never set back again" ? I'd guess that it should be set back to > >> true when it is not an inherited column anymore, that is when its > >> attinhcount reaches zero. > > > Because you have no record of whether it was created locally or > > inherited when originally created. And: do you care? Why? > > The invariant is supposed to be that every attribute has attislocal > true or attinhcount > 0 (or both). Otherwise it has no justification > to exist. I see in the regression database that someone has broken > this invariant; it looks like LIKE inheritance is misimplemented. > I'm going to insist on a fix for that ;-) > > I think that the correct behavior for add/drop is: > > * ADD INHERITS increments attinhcount for every column found to match > a column of the parent. Nothing happens to attislocal. > > * DROP INHERITS decrements attinhcount for every column found to match > a column of the parent. Set attislocal true if attinhcount thereby > goes to zero. > > This makes ADD followed by DROP a certain no-op (if attinhcount was > zero before the ADD, then attislocal must have been true already). > However, DROP followed by ADD is not a no-op since we might wind up > with attislocal true in a column that wasn't that way before. This > seems like a relatively minor thing though. The alternative would > be to delete the child column when it has no definition sources > left; which would be self-consistent but I don't think it's the > behavior we want for this.
Sounds good. -- Simon Riggs EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 3: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq
