Re: psql completion for ids in multibyte string

On Mon, Feb 29, 2016 at 6:32 PM, Thomas Munro
<thomas.munro@enterprisedb.com> wrote:
> On Fri, Feb 26, 2016 at 6:34 PM, Kyotaro HORIGUCHI
> <horiguchi.kyotaro@lab.ntt.co.jp> wrote:
>> Hello, this is the second patch plitted out. This allows
>> multibyte names to be completed in psql.
>>
>> At Fri, 06 Nov 2015 11:47:17 +0900 (Tokyo Standard Time), Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp> wrote
in<20151106.114717.170526268.horiguchi.kyotaro@lab.ntt.co.jp> 
>>> At Thu, 5 Nov 2015 18:32:59 +0900, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp> wrote in
<563B224B.3020400@lab.ntt.co.jp>
>>> > On 2015/11/05 18:10, Kyotaro HORIGUCHI wrote:
>>> > > Hello. I don't know whether this is a bug fix or improvement,
>>> >
>>> > Would it be 50-50? :-)
>>>
>>> Yeah, honestly saying, I doubt that this is valuable but feel
>>> uneasy to see some of the candidates vanish as completon proceeds
>>> for no persuasive reason.
>
> +1 from me, it's entirely reasonable to want to name database objects
> in any human language and use auto-completion.  It's not working today
> as you showed.
>
>> The current version of tab-completion failed to complete names
>> with multibyte characters.
>>
>> =# create table いろは (あ int);
>> =# create table いこい (あ int);
>> =# drop table <tab>
>> "いろは"             hint_plan.           pg_toast.
>> "いこい"             information_schema.  pg_toast_temp_1.
>> ALL IN TABLESPACE    pg_catalog.          public.
>> dbms_stats.          pg_temp_1.
>> postgres=# alter table "い
>> =# drop table "い<tab>
>> =# drop table "い           /* No candidate offered */
>>
>> This is because _complet_from_query counts the string length in
>> bytes, instead of characters. With this patch the candidates will
>> appear.
>>
>> =# drop table "い<tab>
>> "いこい"  "いろは"
>> postgres=# drpo table "い
>
> The patch looks correct to me: it counts characters rather than bytes,
> which is the right thing to do because the value is passed to substr()
> which also works in characters rather than bytes.  I tested with
> "éclair", and without the patch, tab completion doesn't work if you
> press tab after 'é'.  With the patch it does.

OK, but I am a little concerned about this code:
   /* Find something that matches */   if (result && PQresultStatus(result) == PGRES_TUPLES_OK)   {       const char
*item;
       while (list_index < PQntuples(result) &&              (item = PQgetvalue(result, list_index++, 0)))           if
(pg_strncasecmp(text,item, string_length) == 0)               return pg_strdup(item);   } 

Every other use of string_length in this function is using it as the
argument to the SQL substring function, which cares about characters,
not bytes.  But this use seems to care about bytes, not characters.

Am I wrong?

--
Robert Haas
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