Re: case insensitive collation of Greek's sigma

On 26/11/21 9:37 π.μ., Jakub Jedelsky wrote:
> Hello,
Thank you for dealing with Greek!
>
> during our tests of Postgres with ICU we found an issue with ILIKE of upper and lowercase sigma (Σ). The letter has
twolowercase variants σ and ς (at the end of a word). I'm working with en_US and 
 
> en-US-x-icu collations and results are a bit unexpected - they are inverted:
>
> postgres=# SELECT
> postgres-# 'ΣΣ' ILIKE 'σσ' COLLATE "en_US",
> postgres-# 'ΣΣ' ILIKE 'σς' COLLATE "en_US"
> postgres-# ;
>  ?column? | ?column?
> ----------+----------
>  t        | f
> (1 row)
>
> postgres=# SELECT
> postgres-# 'ΣΣ' ILIKE 'σσ' COLLATE "en-US-x-icu",
> postgres-# 'ΣΣ' ILIKE 'σς' COLLATE "en-US-x-icu";
>  ?column? | ?column?
> ----------+----------
>  f        | t
> (1 row)
>
> I run those commands on the latest (14.1) official docker image.
>
> Is it possible to unify the behaviour?And which one is correct from the community point of view?
IMHO all those letters are wrong, the correct S used to be the letter C (equal to the Cyrillic S).
Σ is a new invention, same like σ, the final ς looks a lot like the calligraphic version of c .
>
> If I could start, I think both results are wrong as both should return True. If I got it right, in the background
thereis a lower() function running to compare strings, which is not enough for such 
 
> cases (until the left side isn't taken as a standalone word).
I agree with you all of them should be deducted to a single letter s. Firefox's find recognizes all three (Σ,σ,ς) as
thesame letter.
 
>
> Thanks,
>
> - jj


-- 
Achilleas Mantzios
DBA, Analyst, IT Lead
IT DEPT
Dynacom Tankers Mgmt