On 05/05/2018 10:51 AM, Neto pr wrote:
Dear,
2018-05-05 9:57 GMT-07:00 Adrian Klaver <adrian.klaver@xxxxxxxxxxx
<mailto:adrian.klaver@xxxxxxxxxxx>>:
On 05/05/2018 06:26 AM, Neto pr wrote:
It might help if you explained what 'version with source code
changed by me' means?
Postgresql with modified source code, is that I modified some internal
functions of cost (source code) and parameters in Postgresql.conf so
that it is possible for the DBMS to differentiate cost of read (random
and sequence) and write (random and sequence), this is because reading
in SSDs' and more than 400 times faster than HDD. This is due to
academic research that I am doing.
Seems to me that the above may enter into the difference between
instances. Someone with more knowledge of the Postgres internals then I
would need to comment, contingent on seeing the changes I would presume.
Also from my previous post:
Any reason why the index changed between instances?
Also the schema for the table lineitem from both instances might
help shed light.
see schema of the tables below:
https://docs.snowflake.net/manuals/_images/sample-data-tpch-schema.png
I am using 40g scale, in this way the lineitem table has (40 * 6
million) 240 million of the rows.
Any reason why the index changed between instances?
index on l_orderkey (table lineitem).
Some doubts
- Difference between GroupAggregate and Finalize GroupAggregate
- because some algorithms show measurements on "Disk" and others
on "Memory" example:
- External sort Disk: 52784kB
- quicksort Memory: 47770kB
Because one execution plan was much smaller than the other,
considering that the query is the same and the data are the same.
--------------------------------------------------
select
l_orderkey,
sum(l_extendedprice * (1 - l_discount)) as revenue,
o_orderdate,
o_shippriority
from
customer,
orders,
lineitem
where
c_mktsegment = 'HOUSEHOLD'
and c_custkey = o_custkey
and l_orderkey = o_orderkey
and o_orderdate < date '1995-03-21'
and l_shipdate > date '1995-03-21'
group by
l_orderkey,
o_orderdate,
o_shippriority
order by
revenue desc,
o_orderdate
--------------------------------------------------
best regards
Neto
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx <mailto:adrian.klaver@xxxxxxxxxxx>
Regards
Neto
--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx
