Re: General purpose hashing func in pgbench

From: Ildar Musin <i(dot)musin(at)postgrespro(dot)ru>
To: Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: General purpose hashing func in pgbench
Date: 2018-01-09 16:22:14
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Hello Fabien,

25/12/2017 19:17, Fabien COELHO пишет:
>>> However, the key can be used if controlled so that different values do
>>> not have the same randomization in different part of the script, so as
>>> to avoid using the same patterns for different things if not desirable.
>> Original murmur algorithm accepts seed as a parameter, which can be used
>> for this purpose. I used value itself as a seed in the patch, but I can
>> turn it into a function argument.
> Hmmm. Possibly. However it needs a default, something like
>   x = hash(v[, key])
> with key some pseudo-random value?
Sorry for a long delay. I've added hash() function which is just an
alias for murmur2. I've also utilized variable arguments feature from
least()/greates() functions to make optional seed parameter, but I
consider this as a hack. Should we probably add some infrastructure for
optional arguments? Docs and tests are on their way.


Ildar Musin
Postgres Professional:
Russian Postgres Company

Attachment Content-Type Size
pgbench_hash_v3.patch text/plain 3.3 KB

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