On Mon, Jan 13, 2020 at 10:14:52PM +0900, Michael Paquier wrote: > On Mon, Jan 13, 2020 at 01:09:01PM +0100, Julien Rouhaud wrote: > > But that means an extraneous call to BackendIdGetProc() in that > > case, it seems better to avoid it if we already have the information. > > Note that you cannot make a direct comparison of the result from > GetTempNamespaceBackendId() with MyBackendId, because it is critical > to be able to handle the case of a session which has not created yet > an object on its own temp namespace (this way any temp objects from > previous connections which used the same backend slot can be marked as > orphaned and discarded by autovacuum, the whole point of 246a6c8).
Oh right. > So in order to get a fast-exit path we could do the following: > - Add a routine GetTempNamespace which returns myTempNamespace (the > result can be InvalidOid). > - Add an assertion at the beginning of isTempNamespaceInUse() to make > sure that it never gets called with InvalidOid as input argument. > - Return true as a first step of GetTempNamespaceBackendId() if > namespaceId matches GetTempNamespace(). > > What do you think? Well, since isTempNamespaceInUse is for now only called by autovacuum, and shouldn't change soon, this really feels premature optimzation, so your original approach looks better.
