pgbench - add pseudo-random permutation function

Fabien COELHO <coelho@cri.ensmp.fr>

From: Fabien COELHO <coelho@cri.ensmp.fr>

To: PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>

Date: 2018-07-28T14:03:49Z

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 →

pgbench: Function to generate random permutations.
- 6b258e3d688d 14.0 landed
Add basic support for using the POPCNT and SSE4.2s LZCNT opcodes
- 711bab1e4d19 12.0 cited
Further improve code for probing the availability of ARM CRC instructions.
- a7a7387575b8 11.0 cited

Attachments

pgbench-prp-func-1.patch (text/plain) patch
prp_init.sql (application/x-sql)
prp_analyse.sql (application/x-sql)
prp_gen_vals.sql (application/x-sql)
prp_test_2.sql (application/x-sql)
prp_test_3.sql (application/x-sql)
prp_test_4.sql (application/x-sql)
prp_test_5.sql (application/x-sql)
prp_test_6.sql (application/x-sql)
prp_test_n.sql (application/x-sql)
prp_perf.sql (application/x-sql)

Hello,

This patch adds a pseudo-random permutation function to pgbench. It allows 
to mix non uniform random keys to avoid trivial correlations between 
neighboring values, hence between pages.

The function is a simplistic form of encryption adapted to any size, using 
a few iterations of scramble and scatter phases. The result is not 
cryptographically convincing, nor even statistically, but it is quite 
inexpensive and achieves the desired result. A computation costs 0.22 µs 
per call on my laptop, about three times the cost of a simple function.

Alternative designs, such as iterating over an actual encryption function 
or using some sbox, would lead to much more costly solutions and complex 
code.

I also join a few scripts I used for testing.

-- 
Fabien.