Re: unexpected result from to_tsvector - Mailing list pgsql-hackers

On 14.03.2016 16:22, Shulgin, Oleksandr wrote:
>
> Hm...  now that doesn't look all that consistent to me (after applying
> the patch):
>
> =# select ts_debug('simple', 'aaa@123-yyy.zzz');
>                                   ts_debug
> ---------------------------------------------------------------------------
>   (email,"Email address",aaa@123-yyy.zzz,{simple},simple,{aaa@123-yyy.zzz})
> (1 row)
>
> But:
>
> =# select ts_debug('simple', 'aaa@123_yyy.zzz');
>                          ts_debug
> ---------------------------------------------------------
>   (asciiword,"Word, all ASCII",aaa,{simple},simple,{aaa})
>   (blank,"Space symbols",@,{},,)
>   (uint,"Unsigned integer",123,{simple},simple,{123})
>   (blank,"Space symbols",_,{},,)
>   (host,Host,yyy.zzz,{simple},simple,{yyy.zzz})
> (5 rows)
>
> One can also see that if we only keep the domain name, the result is
> similar:
>
> =# select ts_debug('simple', '123-yyy.zzz');
>                         ts_debug
> -------------------------------------------------------
>   (host,Host,123-yyy.zzz,{simple},simple,{123-yyy.zzz})
> (1 row)
>
> =# select ts_debug('simple', '123_yyy.zzz');
>                        ts_debug
> -----------------------------------------------------
>   (uint,"Unsigned integer",123,{simple},simple,{123})
>   (blank,"Space symbols",_,{},,)
>   (host,Host,yyy.zzz,{simple},simple,{yyy.zzz})
> (3 rows)
>
> But, this only has to do with 123 being recognized as a number, not with
> the underscore:
>
> =# select ts_debug('simple', 'abc_yyy.zzz');
>                         ts_debug
> -------------------------------------------------------
>   (host,Host,abc_yyy.zzz,{simple},simple,{abc_yyy.zzz})
> (1 row)
>
> =# select ts_debug('simple', '1abc_yyy.zzz');
>                         ts_debug
> -------------------------------------------------------
>   (host,Host,1abc_yyy.zzz,{simple},simple,{1abc_yyy.zzz})
> (1 row)
>
> In fact, the 123-yyy.zzz domain is not valid either according to the RFC
> (subdomain can't start with a digit), but since we already allow it,
> should we not allow 123_yyy.zzz to be recognized as a Host?  Then why
> not recognize aaa@123_yyy.zzz as an email address?
>
> Another option is to prohibit underscore in recognized host names, but
> this has more breakage potential IMO.
>
> --
> Alex
>

It seems reasonable to me. I like more first option. But I am not 
confident that we should allow 123_yyy.zzz to be recognized as a Host.

By the way, in this question http://webmasters.stackexchange.com/a/775 
you can see examples of domain names with numbers (but not subdomains).

If there are not objections from others, I will send a new patch today 
later or tomorrow with 123_yyy.zzz recognizing.

-- 
Artur Zakirov
Postgres Professional: http://www.postgrespro.com
Russian Postgres Company