Subject: Re: [PATCH] Feature improvement for CLOSE, FETCH, MOVE tab completion
To: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: Shinya11.Kato@nttdata.com,
 PostgreSQL-development <pgsql-hackers@postgresql.org>
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From: Fujii Masao <masao.fujii@oss.nttdata.com>
Message-ID: <80b6a07a-9249-bf08-6add-bdda1ccb0659@oss.nttdata.com>
Date: Thu, 7 Jan 2021 13:30:32 +0900
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On 2021/01/07 12:42, Masahiko Sawada wrote:
> On Thu, Jan 7, 2021 at 10:59 AM Fujii Masao <masao.fujii@oss.nttdata.com> wrote:
>>
>>
>>
>> On 2021/01/07 10:01, Masahiko Sawada wrote:
>>> On Wed, Jan 6, 2021 at 3:37 PM <Shinya11.Kato@nttdata.com> wrote:
>>>>
>>>>> +#define Query_for_list_of_cursors \
>>>>> +" SELECT name FROM pg_cursors"\
>>>>>
>>>>> This query should be the following?
>>>>>
>>>>> " SELECT pg_catalog.quote_ident(name) "\
>>>>> "   FROM pg_catalog.pg_cursors "\
>>>>> "  WHERE substring(pg_catalog.quote_ident(name),1,%d)='%s'"
>>>>>
>>>>> +/* CLOSE */
>>>>> +      else if (Matches("CLOSE"))
>>>>> +              COMPLETE_WITH_QUERY(Query_for_list_of_cursors
>>>>> +                                                      " UNION ALL SELECT 'ALL'");
>>>>>
>>>>> "UNION ALL" should be "UNION"?
>>>>
>>>> Thank you for your advice, and I corrected them.
>>>>
>>>>>> +               COMPLETE_WITH_QUERY(Query_for_list_of_cursors
>>>>>> +                                                       " UNION SELECT 'ABSOLUTE'"
>>>>>> +                                                       " UNION SELECT 'BACKWARD'"
>>>>>> +                                                       " UNION SELECT 'FORWARD'"
>>>>>> +                                                       " UNION SELECT 'RELATIVE'"
>>>>>> +                                                       " UNION SELECT 'ALL'"
>>>>>> +                                                       " UNION SELECT 'NEXT'"
>>>>>> +                                                       " UNION SELECT 'PRIOR'"
>>>>>> +                                                       " UNION SELECT 'FIRST'"
>>>>>> +                                                       " UNION SELECT 'LAST'"
>>>>>> +                                                       " UNION SELECT 'FROM'"
>>>>>> +                                                       " UNION SELECT 'IN'");
>>>>>>
>>>>>> This change makes psql unexpectedly output "FROM" and "IN" just after "FETCH".
>>>>>
>>>>> I think "FROM" and "IN" can be placed just after "FETCH". According to
>>>>> the documentation, the direction can be empty. For instance, we can do
>>>>> like:
>>>>
>>>> Thank you!
>>>>
>>>>> I've attached the patch improving the tab completion for DECLARE as an
>>>>> example. What do you think?
>>>>>
>>>>> BTW according to the documentation, the options of DECLARE statement
>>>>> (BINARY, INSENSITIVE, SCROLL, and NO SCROLL) are order-sensitive.
>>>>>
>>>>> DECLARE name [ BINARY ] [ INSENSITIVE ] [ [ NO ] SCROLL ]
>>>>>      CURSOR [ { WITH | WITHOUT } HOLD ] FOR query
>>>>>
>>>>> But I realized that these options are actually order-insensitive. For
>>>>> instance, we can declare a cursor like:
>>>>>
>>>>> =# declare abc scroll binary cursor for select * from pg_class;
>>>>> DECLARE CURSOR
>>>>>
>>>>> The both parser code and documentation has been unchanged from 2003.
>>>>> Is it a documentation bug?
>>>>
>>>> Thank you for your patch, and it is good.
>>>> I cannot find the description "(BINARY, INSENSITIVE, SCROLL, and NO SCROLL) are order-sensitive."
>>>> I saw "The key words BINARY, INSENSITIVE, and SCROLL can appear in any order." , according to the documentation.
>>>
>>> Thanks, you're right. I missed that sentence. I still don't think the
>>> syntax of DECLARE statement in the documentation doesn't match its
>>> implementation but I agree that it's order-insensitive.
>>>
>>>> I made a new patch, but the amount of codes was large due to order-insensitive.
>>>
>>> Thank you for updating the patch!
>>>
>>> Yeah, I'm also afraid a bit that conditions will exponentially
>>> increase when a new option is added to DECLARE statement in the
>>> future. Looking at the parser code for DECLARE statement, we can put
>>> the same options multiple times (that's also why I don't think it
>>> matches). For instance,
>>>
>>> postgres(1:44758)=# begin;
>>> BEGIN
>>> postgres(1:44758)=# declare test binary binary binary cursor for
>>> select * from pg_class;
>>> DECLARE CURSOR
>>>
>>> So how about simplify the above code as follows?
>>>
>>> @@ -3005,8 +3014,23 @@ psql_completion(const char *text, int start, int end)
>>>       else if (Matches("DECLARE", MatchAny))
>>>           COMPLETE_WITH("BINARY", "INSENSITIVE", "SCROLL", "NO SCROLL",
>>>                         "CURSOR");
>>> +   /*
>>> +    * Complete DECLARE <name> with one of BINARY, INSENSITIVE, SCROLL,
>>> +    * NO SCROLL, and CURSOR. The tail doesn't match any keywords for
>>> +    * DECLARE, assume we want options.
>>> +    */
>>> +   else if (HeadMatches("DECLARE", MatchAny, "*") &&
>>> +            TailMatches(MatchAnyExcept("CURSOR|WITH|WITHOUT|HOLD|FOR")))
>>> +       COMPLETE_WITH("BINARY", "INSENSITIVE", "SCROLL", "NO SCROLL",
>>> +                     "CURSOR");
>>
>> This change seems to cause "DECLARE ... CURSOR FOR SELECT <tab>" to
>> unexpectedly output BINARY, INSENSITIVE, etc.
> 
> Indeed. Is the following not complete but much better?

Yes, I think that's better.

> 
> @@ -3002,11 +3011,18 @@ psql_completion(const char *text, int start, int end)
>                              " UNION SELECT 'ALL'");
> 
>   /* DECLARE */
> -   else if (Matches("DECLARE", MatchAny))
> -       COMPLETE_WITH("BINARY", "INSENSITIVE", "SCROLL", "NO SCROLL",
> -                     "CURSOR");
> +   /*
> +   * Complete DECLARE <name> with one of BINARY, INSENSITIVE, SCROLL,
> +   * NO SCROLL, and CURSOR. If the tail is any one of options, assume we
> +   * still want options.
> +   */
> +   else if (Matches("DECLARE", MatchAny) ||
> +            TailMatches("BINARY|INSENSITIVE|SCROLL|NO"))
> +       COMPLETE_WITH("BINARY", "INSENSITIVE", "SCROLL", "NO SCROLL", "CURSOR");

This change seems to cause "DECLARE ... NO <tab>" to unexpectedly output
"NO SCROLL". Also this change seems to cause "COPY ... (FORMAT BINARY <tab>"
to unexpectedly output BINARY, CURSOR, etc.

Regards,

-- 
Fujii Masao
Advanced Computing Technology Center
Research and Development Headquarters
NTT DATA CORPORATION