On Thu, Dec 6, 2018 at 11:13 AM Amit Kapila <amit.kapila16@gmail.com> wrote: > > On Thu, Dec 6, 2018 at 10:03 AM Pavel Stehule <pavel.stehule@gmail.com> wrote: > > > > čt 6. 12. 2018 v 5:02 odesílatel Mithun Cy <mithun.cy@enterprisedb.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? I though it was sense just for current format.
Regards
Pavel
Length of each item. (all Items are identical) ===================================== postgres=# SELECT lp_len FROM zheap_page_items(get_raw_page('pgbench_zheap', 9)) limit 1; lp_len -------- 102 (1 row)