> On 26 Jul 2024, at 14:30, Andreas Karlsson <andr...@proxel.se> wrote:
>
> I feel the tricky part about doing that is that we need to make sure the fake
> LSNs are all less than the current real LSN when the index build completes
> and while that normally should be the case we will have a almost never
> exercised code path for when the fake LSN becomes bigger than the real LSN
> which may contain bugs. Is that really worth it to optimize.
>
> But if we are going to use fake LSN: since the index being built is not
> visible to any scans we do not have to use GetFakeLSNForUnloggedRel() but
> could use an own counter in shared memory in the GISTShared struct for this
> specific index which starts at FirstNormalUnloggedLSN. This would give us
> slightly less contention plus decrease the risk (for good and bad) of the
> fake LSN being larger than the real LSN.
+1 for atomic counter in GISTShared.
BTW we can just reset LSNs to GistBuildLSN just before doing
log_newpage_range().
Best regards, Andrey Borodin.
