[HACKERS] [WIP] Zipfian distribution in pgbench - Mailing list pgsql-hackers

Hello!

PostgreSQL shows very bad results in YCSB Workload A (50% SELECT and 50% UPDATE of random row by PK) on benchmarking
withbig number of clients using Zipfian distribution. MySQL also has decline but it is not significant as it is in
PostgreSQL.MongoDB does not have decline at all. And if pgbench would have Zipfian distribution random number
generator,everyone will be able to make research on this topic without using YCSB.  

This is the reason why I am currently working on random_zipfian function.

The bottleneck of algorithm that I use is that it calculates zeta function (it has linear complexity -
https://en.wikipedia.org/wiki/Riemann_zeta_function).It my cause problems on generating huge amount of big numbers.  

That’s why I added caching for zeta value. And it works good for cases when random_zipfian called with same parameters
inscript. For example: 

…
\set a random_zipfian(1, 100, 1.2)
\set b random_zipfian(1, 100, 1.2)
…

In other case, second call will override cache of first and caching does not make any sense:
…
\set a random_zipfian(1, 100, 1.2)
\set b random_zipfian(1, 200, 1.4)
…

That’s why I have a question: should I implement support of caching zeta values for calls with different parameters, or
not? 

P.S. I attaching patch and script - analogue of YCSB Workload A.
Run benchmark with command:
$ pgbench -f  ycsb_read_zipf.sql -f  ycsb_update_zipf.sql

On scale = 10(1 million rows) it gives following results on machine with 144 cores(with synchronous_commit=off):
    nclients    tps
    1        8842.401870
    2        18358.140869
    4        45999.378785
    8        88713.743199
    16        170166.998212
    32        290069.221493
    64        178128.030553
    128        88712.825602
    256        38364.937573
    512        13512.765878
    1000     6188.136736

—
Thanks and Regards,
Alik Khilazhev
Postgres Professional:
http://www.postgrespro.com
The Russian Postgres Company
-- 
Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-hackers

Attachment

pgsql-hackers by date:

Previous
From: "K S, Sandhya (Nokia - IN/Bangalore)"
Date:
Subject: Re: [HACKERS] Postgres process invoking exit resulting in sh-QUITcore
Next
From: Michael Banck
Date:
Subject: Re: [HACKERS] New partitioning - some feedback