Horton

Re: pgbench - add pseudo-random permutation function

Fabien COELHO <coelho@cri.ensmp.fr>

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From: Fabien COELHO <coelho@cri.ensmp.fr>
To: Hironobu SUZUKI <hironobu@interdb.jp>
Cc: PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Date: 2018-09-16T20:05:28Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. pgbench: Function to generate random permutations.

  2. Add basic support for using the POPCNT and SSE4.2s LZCNT opcodes

  3. Further improve code for probing the availability of ARM CRC instructions.

Attachments

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.