Replace md5() with hashtext()

[akostadinov]

Hello. When PostgreSQL 15+ is running in FIPS mode, it has all usage of MD5 disabled. One would see an error message:

ERROR -- : [ActiveJob] Failed enqueuing UpdateJob to Que(default): PG::InternalError (ERROR: could not compute MD5 hash: unsupported

The culprit seems to be usage of MD5 for load balancing:

que/lib/que/migrations/5/up.sql

Line 41 in 17fb2c3

ORDER BY md5(pid::text || id::text)

I think the solution is to use a hashing algorithm that doesn't bother FIPS. And PostgreSQL's built-in hashtext() function seems to check. As far as I understand the exact hashing algorithm is irrelevant.

As a bonus, that hashtext function is 5 times faster than md5. On my laptop it shows 142ms vs 27ms for 100k iterations.

zync=# \timing on
Timing is on.
zync=# SELECT count(distinct md5(n::text)) FROM generate_series(1, 100000) n;
 count  
--------
 100000
(1 row)

Time: 142.511 ms

zync=# SELECT count(distinct hashtext(n::text)) FROM generate_series(1, 100000) n;
 count  
--------
 100000
(1 row)

Time: 27.405 ms

-- I tried this on PostgreSQL 15 and 18, but hashtext seems to be old so probably will support earlier versions as well.