Re: zheap: a new storage format for PostgreSQL

čt 6. 12. 2018 v 8:08 odesílatel Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
napsal:

> On Thu, Dec 6, 2018 at 12:30 PM Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
> wrote:
> >
> > čt 6. 12. 2018 v 7:55 odesílatel Mithun Cy <mithun(dot)cy(at)enterprisedb(dot)com>
> napsal:
> >>
> >> On Thu, Dec 6, 2018 at 11:13 AM Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
> wrote:
> >> >
> >> > On Thu, Dec 6, 2018 at 10:03 AM Pavel Stehule <
> pavel(dot)stehule(at)gmail(dot)com> wrote:
> >> > >
> >> > > čt 6. 12. 2018 v 5:02 odesílatel Mithun Cy <
> mithun(dot)cy(at)enterprisedb(dot)com> napsal:
> >> > >>
> >> > >> COPY command seems to have improved very slightly with zheap in
> both with size of wal and execution time. I also did some tests with insert
> statement where I could see some regression in zheap when compared to heap
> with respect to execution time. With further more investigation I will
> reply here.
> >> > >>
> >> > >
> >> > > 20% of size reduction looks like effect of fill factor.
> >> > >
> >> >
> >> > I think it is because of smaller zheap tuple sizes. Mithun can tell
> >> > more about setup whether he has used different fillfactor or anything
> >> > else which could lead to such a big difference.
> >>
> >> Yes default fillfactor is unaltered, zheap tuples sizes are less and
> >> alinged each at 2 Bytes
> >>
> >
> > I am sorry, I know zero about zheap - does zheap use fill factor? if
> yes, why?
> >
>
> Good question. It is required because tuples can expand (Update tuple
> to bigger length). In such cases, we try to perform in-place update
> if there is a space in the page. So, having fillfactor can help.
>
>
Thank you for reply :)

Pavel

--
> With Regards,
> Amit Kapila.
> EnterpriseDB: http://www.enterprisedb.com
>