On Thu, 29 Aug 2024 at 16:53, Frédéric Yhuel <frederic.yh...@dalibo.com> wrote:
> > > On 8/23/24 12:51, Frédéric Yhuel wrote: > > > > > > On 8/23/24 12:02, Rafia Sabih wrote: > >> On the other hand, this got me thinking about the purpose of this > >> space information. > >> If we want to understand that there's still some space for the tuples > >> in a page, then using PageGetExactFreeSpace is not doing justice in > >> case of heap page, because we will not be able to add any more tuples > >> there if there are already MaxHeapTuplesPerPage tuples there. > > > > We won't be able to add, but we will be able to update a tuple in this > > page. > > Sorry, that's not true. > > So in this marginal case we have free space that's unusable in practice. > No INSERT or UPDATE (HOT or not) is possible inside the page. > > I don't know what pgstattuple should do in this case. > > However, we should never encounter this case in practice (maybe on some > exotic architectures with strange alignment behavior?). As I said, I > can't fit more than 226 tuples per page on my machine, while > MaxHeapTuplesPerPage is 291. Am I missing something? > > Besides, pgstattuple isn't mission critical, is it? > Yes, also as stated before I am not sure of the utility of this field in real-world scenarios. So, I can not comment more on that. That was just one thought that popped into my head. Otherwise, the idea seems fine to me. > > So I think we should just use PageGetExactFreeSpace(). > > Here is a v3 patch. It's the same as v2, I only removed the last > paragraph in the commit message. > Thanks for the new patch. LGTM. > > Thank you Rafia and Andreas for your review and test. > Thanks to you too. > > Best regards, > Frédéric -- Regards, Rafia Sabih
