Re: Wrong value in metapage of GIN INDEX.

Dear Tom Lane.

On Tue, Nov 5, 2019 at 3:55 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> "imai(dot)yoshikazu(at)fujitsu(dot)com" <imai(dot)yoshikazu(at)fujitsu(dot)com> writes:
> > Moon-san, kuroda.keisuke-san
> > On Thu, Aug 29, 2019 at 8:20 AM, Moon, Insung wrote:
> >> The patch is very simple.
> >> Fix to increase the value of nEntries only when a non-duplicate GIN index leaf added.
>
> > Does nentries show the number of entries in the leaf pages?
> > If so, the fix seems to be correct.
>
> I looked at this issue. The code in ginEntryInsert is not obviously wrong
> by itself; it depends on what you think nEntries is supposed to count.
> However, ginvacuum.c updates nEntries to the sum of PageGetMaxOffsetNumber()
> across all the index's leaf pages, ie the number of surviving leaf items.
>
> It's hard to see how ginvacuum could reverse-engineer a value that would
> match what ginEntryInsert is doing, so probably we ought to define
> nEntries as the number of leaf items, which seems to make the proposed
> patch correct. (It could use a bit more commentary though.)
>
> I'm inclined to apply this to HEAD only; it doesn't seem significant
> enough to justify back-patching.

Thank you for review and push to patch.
Yes. I don't think it's a bug that has a big impact like your opinion.

Best regards.
Moon.

>
> regards, tom lane