On Mon, Sep 3, 2018 at 2:44 PM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> On Mon, Sep 3, 2018 at 8:37 AM, Amit Kapila <amit.kapila16@gmail.com> wrote:
> > On Sat, Sep 1, 2018 at 10:28 AM Dilip Kumar <dilipbalaut@gmail.com> wrote:
> >>
> >> I think if we compute with below formula which I suggested upthread
> >>
> >> #define HASH_MAX_BITMAPS Min(BLCKSZ / 8, 1024)
> >>
> >> then for BLCKSZ 8K and bigger, it will remain the same value where it
> >> does not overrun. And, for the small BLCKSZ, I think it will give
> >> sufficient space for the hash map. If the BLCKSZ is 1K then the sizeof
> >> (HashMetaPageData) + sizeof (HashPageOpaque) = 968 which is very close
> >> to the BLCKSZ.
> >>
> >
> > Yeah, so at 1K, the value of HASH_MAX_BITMAPS will be 128 as per above
> > formula which is what it was its value prior to the commit 620b49a1.
> > I think it will be better if you add a comment in your patch
> > indicating the importance/advantage of such a formula.
> >
> I have added the comments.
>
Thanks, I will look into it. Can you please do some pg_upgrade tests
to ensure that this doesn't impact the upgrade? You can create
hash-index and populate it with some data in version 10 and try
upgrading to 11 after applying this patch. You can also try it with
different block-sizes.
--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com