Re: General purpose hashing func in pgbench

>> Hmm. I do not think that we should want a shared seed value. The seed
>> should be different for each call so as to avoid undesired
>> correlations. If wanted, correlation could be obtained by using an
>> explicit identical seed.
>>
>> ISTM that the best way to add the seed is to call random() when the
>> second arg is missing in make_func. Also, this means that the executor
>> would always get its two arguments, so it would simplify the code there.
>>
> Ok, I think I understand what you meant. You meant the case like following:
>
> \set x random(1, 100)
> \set h1 hash(:x)
> \set h2 hash(:x)  -- will have different seed from h1
>
> so that different instances of hash function within one script would
> have different seeds. Yes, that is a good idea, I can do that.

Yes, exactly. What is desirable may depend on the use case, though.

-- 
Fabien.