> On Mon, Jan 23, 2023 at 07:09:27PM +0100, Pavel Stehule wrote: > po 23. 1. 2023 v 15:25 odesílatel Dmitry Dolgov <9erthali...@gmail.com> > napsal: > > > > On Sun, Jan 22, 2023 at 07:47:07PM +0100, Pavel Stehule wrote: > > > pá 20. 1. 2023 v 21:35 odesílatel Dmitry Dolgov <9erthali...@gmail.com> > > > napsal: > > > > > > > * I think it was already mentioned in the thread, there seems to be > > not a > > > > single usage of CHECK_FOR_INTERRUPTS in session_variable.c . But some > > > > number > > > > of loops over the sessionvars are implemented, are they always going > > to > > > > be > > > > small enough to not make any troubles? > > > > > > > > > > The longest cycle is a cycle that rechecks actively used variables > > against > > > system catalog. No cycle depends on the content of variables. > > > > Right, but what about the cases with huge number of variables? Not > > saying it could be in any sense common, but possible to do. > > > > Now I tested 10K variables (with enabled assertions, without it is should > be faster) > > [...] > > I can be wrong, but from these numbers I don't think so these sync cycles > should to contain CHECK_FOR_INTERRUPTS > > What do you think?
Well, there is always possibility someone will create more variables than any arbitrary limit we have tested for. But I see your point and don't have a strong opinion about this, so let's keep it as it is :) > > > > * sync_sessionvars_all explains why is it necessary to copy > > > > xact_recheck_varids: > > > > > > > > When we check the variables, the system cache can be > > > > invalidated, > > > > and xact_recheck_varids can be enhanced. > > > > > > > > I'm not quite following what the "enhancement" part is about? Is > > > > xact_recheck_varids could be somehow updated concurrently with the > > loop? > > > > > > > > > > Yes. pg_variable_cache_callback can be called when > > > is_session_variable_valid is executed. > > > > > > Maybe "extended" can be a better word instead of "enhanced"? I > > reformulated > > > this comment > > > > Yeah, "extended" sounds better. But I was mostly confused about the > > mechanism, if the cache callback can interrupt the execution at any > > moment when called, that would explain it. > > > > patch from yesterday has extended comment in this area :-) Thanks!
