Re: pgbench - add pseudo-random permutation function - Mailing list pgsql-hackers

From Fabien COELHO
Subject Re: pgbench - add pseudo-random permutation function
Date
Msg-id alpine.DEB.2.21.1809162200180.1834@lancre
Whole thread Raw
In response to Re: pgbench - add pseudo-random permutation function  (Fabien COELHO <coelho@cri.ensmp.fr>)
Responses Re: pgbench - add pseudo-random permutation function
List pgsql-hackers
Hello Hironobu-san,

Here is a v4, based on our out-of-list discussion:
  - the mask function is factored out
  - the popcount builtin is used if available

> Attached a v3, based on your fix, plus some additional changes:
> - explicitly declare unsigned variables where appropriate, to avoid casts
> - use smaller 24 bits primes instead of 27-29 bits
> - add a shortcut for multiplier below 24 bits and y value below 40 bits,
>   which should avoid the manually implemented multiplication in most
>   practical cases (tables with over 2^40 rows are pretty rare...).
> - change the existing shortcut to look a the number of bits instead of
>   using 32 limits.
> - add a test for minimal code coverage with over 40 bits sizes
> - attempt to improve the documentation
> - some comments were updates, hopefully for the better

-- 
Fabien.
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