Re: remove undocumented assign syntax from plpgsql doc
| От | Pavel Stehule |
|---|---|
| Тема | Re: remove undocumented assign syntax from plpgsql doc |
| Дата | |
| Msg-id | CAFj8pRAyAOi9ZJbxMBPkW+r03n+zQm6idojWWH2n17h8NGyXBA@mail.gmail.com обсуждение исходный текст |
| Ответ на | Re: remove undocumented assign syntax from plpgsql doc (Bruce Momjian <bruce@momjian.us>) |
| Ответы |
Re: remove undocumented assign syntax from plpgsql doc
|
| Список | pgsql-docs |
2014/1/12 Bruce Momjian <bruce@momjian.us>
On Sat, Jan 11, 2014 at 10:06:27PM +0100, Pavel Stehule wrote:OK, docs updated for that. I assume OPEN and FOR also can take := or =,
>
>
>
> 2014/1/11 Tom Lane <tgl@sss.pgh.pa.us>
>
> Bruce Momjian <bruce@momjian.us> writes:
> > Oh, I think you are right. I have reverted the patch. Attached is
> > proposed documentation for '='.
>
> Meh. Variable initialization is only one of multiple cases (assignment,
> GET DIAGNOSTICS; maybe others, I've not examined the grammar). Also,
> if we do it like this, we're implying that both := and = are equally
> preferred, which might not be the impression we want to leave.
>
>
> GET DIAGNOSTICS is defined by standard - and there "=" should be allowed only -
> although we allow ":=" too. It is a embedded SQL statement - although it is
> implemented as plpgsql statement.
right?Comment updated. Patch attached.
> Same situation is with UPDATE statement - we don't allow ":=" there.
>
>
>
> I'd be a bit inclined to just stick a NOTE somewhere saying that "="
> can be used in place of ":=" for assignment.
>
>
> ok
>
> If we accept it and we close this topic, then following comment should be
> removed
>
> assign_operator : '=' /* not documented because it might be removed someday *
Still I am missing message about preferred syntax (or we should to enhance GET DIAGNOSTICS doc about proprietary syntax).
PL/pgSQL, PL/SQL is mix of two languages: ADA and SQL - and their designers decided so embedded SQL statements will be placed in native SQL syntax (and ADA in simplified ADA syntax)
We have to find a agreement what we will prefer for PL/pgSQL:
The assign statement is "ADA" statement - ":=" is preferred
The GET DIAGNOSTICS is "SQL" statement - "=" is preferred
A newer SQL/PSM was designed differently - without this dichotomy - A assignment is emphased by syntax SET varname = value
A proper syntax is good information what is coming from - and It is good mental helper to understand a philosophy of stored procedures (that shares concepts with PL/SQL). Next argument is similarity with PL/SQL and SQL PL. This statement (GET DIAGNOSTICS) is supported on both environments and only "=" is allowed there.
Regards
Pavel
--
Bruce Momjian <bruce@momjian.us> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ Everyone has their own god. +
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