Re: psql completion for ids in multibyte string

On Wed, Mar 2, 2016 at 7:54 AM, Robert Haas <robertmhaas@gmail.com> wrote:
> 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?

Ugh, and the other problem is that string_length is always 0 there if
state isn't 0 (in master it is static so that the value is reused for
subsequent calls, but this patch made it automatic).

I think we should leave string_length as it is and use a new variable
for character-based length, as in the attached.

--
Thomas Munro
http://www.enterprisedb.com