Re: PL/pgSQL PERFORM with CTE - Mailing list pgsql-hackers
| From | Pavel Stehule |
|---|---|
| Subject | Re: PL/pgSQL PERFORM with CTE |
| Date | |
| Msg-id | CAFj8pRCYHty_W6_ziijd6FqATx9NoMsGppKP5zTiwX_SyNT8qA@mail.gmail.com Whole thread Raw |
| In response to | Re: PL/pgSQL PERFORM with CTE ("David E. Wheeler" <david@justatheory.com>) |
| Responses |
Re: PL/pgSQL PERFORM with CTE
|
| List | pgsql-hackers |
2013/8/29 David E. Wheeler <david@justatheory.com>
On Aug 29, 2013, at 1:11 PM, Pavel Stehule <pavel.stehule@gmail.com> wrote:So YIELD or implement PL/PSM.
> I cannot to say what is good design for PL/pgSQL - only I feel so some variant of RETURN statement is not good, because semantic is significantly different. And I see a increasing inconsistency between a original ADA and PL/pgSQL.
We can discussed about syntax later - now it is offtopic and it is too early - still we miss a procedures.
PL/pgSQL is not PSM.
> Sure, When I am thinking about PSM, I am thinking about T-SQL syntax, but there is little bit simpler situation - there is a precedent in PSM implementation in MySQL and some other new databases.
yes, I know it well - although some syntax is shared - CASE statements
No reason SELECT could not work just a well.
> so main problem is a impossibility to write
>
> BEGIN
> CALL fce()
>
> or
>
> BEGIN
> fce();
>
> A workaround in Postgres is PERFORM - and I really has nothing again to remove PERFORM for start of VOID functions!
No, originally, there was a target of compatibility with PL/SQL (more or less in some time), and PL/SQL disallow unbound SELECT.
More - PL/SQL allow a direct procedure call - so some like PERFORM is useless there.
Well, it was an aside, but points out another problem with PERFORM: It doesn't really exist. I gets replaced with SELECT internally, leading to confusing error messages. Solution: Allow SELECT instead of PERFORM.
> A unhelpful error message has zero relevant to topic - just almost all in PL/pgSQL is SELECT.I agree it would be nice if it didn't report SELECT there, but at least it's not *removing* anything from what you see in the source.
> Do you would to remove a ":=" statement too?
>
> postgres=# do $$declare x int; begin x := notexisting(10); end; $$ ;
> ERROR: function notexisting(integer) does not exist
> LINE 1: SELECT notexisting(10)
> ^
> HINT: No function matches the given name and argument types. You might need to add explicit type casts.
> QUERY: SELECT notexisting(10)
> CONTEXT: PL/pgSQL function inline_code_block line 1 at assignment
It was a little bit a irony. I am think now so all problems about PERFORM is based on porting PL/SQL environment (that was a classic simplified ADA) to PostgreSQL without procedures. So PERFORM was a designed for evaluation of something like procedures - but there was nothing in this time - a VOID functions are younger. Without PERFORM we didn't do this talk.
Still I don't think so correct solution is enabling a unbound SELECTs, but correct is a fix a PERFORM and remove a necessity to use a PERFORM for call of VOID functions.
Regards
Pavel
Pavel
Best,
David
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