Re: zheap: a new storage format for PostgreSQL

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.

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