Re: General purpose hashing func in pgbench

From: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
To: Ildar Musin <i(dot)musin(at)postgrespro(dot)ru>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: General purpose hashing func in pgbench
Date: 2018-01-26 06:28:19
Message-ID: alpine.DEB.2.20.1801260714070.26762@lancre
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Hello Ildar,

Applies, compiles, runs.

I still have a few very minor comments, sorry for this (hopefully) last
iteration from my part. I'm kind of iterative...

The XML documentation source should avoid a paragraph on one very long
line, but rather be indented like other sections.

I'd propose simplify the second part:

Hash functions can be used, for example, to modify the distribution of
<literal>random_zipfian</literal> or <literal>random_exponential</literal>
functions in order to obtain scattered distribution.
Thus the following pgbench script simulates possible real world workload
typical for social media and blogging platforms where few accounts
generate excessive load:

->

Hash functions can be used to scatter the distribution of random
functions such as <literal>random_zipfian</literal> or
<literal>random_exponential</literal>.
For instance, the following pgbench script simulates possible real
world workload typical for social media and blogging platforms where
few accounts generate excessive load:

Comment the Assert(0) as an internal error that cannot happen.

I'd suggest to compact the execution code by declaring int64 variable and
coerce to int in one go, like the integer bitwise functions. I'm in favor
to keeping them in their own case and not reuse this one.

--
Fabien.

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