Horton

Re: pgbench - add pseudo-random permutation function

Fabien COELHO <coelho@cri.ensmp.fr>

View thread
From: Fabien COELHO <coelho@cri.ensmp.fr>
To: Andres Freund <andres@anarazel.de>
Cc: Hironobu SUZUKI <hironobu@interdb.jp>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Alvaro Herrera <alvherre@2ndquadrant.com>
Date: 2019-03-03T08:55:58Z
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

> Indeed, the patch needs a rebase & conflit resolution. I'll do it. Later.

Here is an update:

  - take advantage of pg_bitutils (although I noted that the "slow"
    popcount there could be speeded-up and shorten with a bitwise operator
    implementation that I just removed from pgbench).

  - add comments about the bijective transformations in the code.

As already stated, this function makes sense for people who want to test 
performance with pgbench using non uniform rands. If you do not want to do 
that, you will probably find the function pretty useless. I can't help it.

Also, non uniform rands is also a way to test pg lock contention behavior.

-- 
Fabien.