Thread: syntax question

syntax question

From
Marc Millas
Date:
Hi,

within a function, I want to create another function.
no pb.
but if I write:
declare bidule text;
begin
bidule:='myfunc';
create function bidule() ...


it does create a function named bidule and not myfunc.
so I am obviously missing something too obvious.

can someone help ?
thanks



Marc MILLAS
Senior Architect
+33607850334

Re: syntax question

From
Bruce Momjian
Date:
On Thu, Jun  3, 2021 at 08:58:03PM +0200, Marc Millas wrote:
> Hi,
> 
> within a function, I want to create another function.
> no pb.
> but if I write:
> declare bidule text;
> begin
> bidule:='myfunc';
> create function bidule() ...
> 
> 
> it does create a function named bidule and not myfunc.
> so I am obviously missing something too obvious.

You can't create functions inside of functions;  same for procedures.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  If only the physical world exists, free will is an illusion.




Re: syntax question

From
Adrian Klaver
Date:
On 6/3/21 12:01 PM, Bruce Momjian wrote:
> On Thu, Jun  3, 2021 at 08:58:03PM +0200, Marc Millas wrote:
>> Hi,
>>
>> within a function, I want to create another function.
>> no pb.
>> but if I write:
>> declare bidule text;
>> begin
>> bidule:='myfunc';
>> create function bidule() ...
>>
>>
>> it does create a function named bidule and not myfunc.
>> so I am obviously missing something too obvious.
> 
> You can't create functions inside of functions;  same for procedures.
> 

Sure you can:

CREATE OR REPLACE FUNCTION public.test_fnc()
  RETURNS void
  LANGUAGE plpgsql
AS $function$
DECLARE
      bidule text;
BEGIN
bidule:='myfunc';
EXECUTE  'create function ' ||  bidule || '() RETURNS void language 
plpgsql AS $fnc$ BEGIN END; $fnc$ ';
END;


$function$

select test_fnc();
  test_fnc
----------

  \df myfunc
                         List of functions
  Schema |  Name  | Result data type | Argument data types | Type
--------+--------+------------------+---------------------+------
  public | myfunc | void             |                     | func


Whether you should is another question.


-- 
Adrian Klaver
adrian.klaver@aklaver.com



Re: syntax question

From
Tom Lane
Date:
Adrian Klaver <adrian.klaver@aklaver.com> writes:
> On 6/3/21 12:01 PM, Bruce Momjian wrote:
>> On Thu, Jun  3, 2021 at 08:58:03PM +0200, Marc Millas wrote:
>>> within a function, I want to create another function.

>> You can't create functions inside of functions;  same for procedures.

> Sure you can:

Yeah.  The actual problem here is that Marc is expecting variable
substitution to occur within a utility (DDL) statement, which it
doesn't.  The workaround is to build the command as a string and
use EXECUTE, as Adrian illustrated:

> EXECUTE  'create function ' ||  bidule || '() RETURNS void language
> plpgsql AS $fnc$ BEGIN END; $fnc$ ';

This is not terribly well explained in the existing docs.  I tried
to improve the explanation awhile ago in HEAD:

https://www.postgresql.org/docs/devel/plpgsql-statements.html#PLPGSQL-STATEMENTS-GENERAL-SQL

            regards, tom lane



Re: syntax question

From
Bruce Momjian
Date:
On Thu, Jun  3, 2021 at 03:21:15PM -0400, Tom Lane wrote:
> Adrian Klaver <adrian.klaver@aklaver.com> writes:
> > On 6/3/21 12:01 PM, Bruce Momjian wrote:
> >> On Thu, Jun  3, 2021 at 08:58:03PM +0200, Marc Millas wrote:
> >>> within a function, I want to create another function.
> 
> >> You can't create functions inside of functions;  same for procedures.
> 
> > Sure you can:
> 
> Yeah.  The actual problem here is that Marc is expecting variable
> substitution to occur within a utility (DDL) statement, which it
> doesn't.  The workaround is to build the command as a string and
> use EXECUTE, as Adrian illustrated:
> 
> > EXECUTE  'create function ' ||  bidule || '() RETURNS void language 
> > plpgsql AS $fnc$ BEGIN END; $fnc$ ';
> 
> This is not terribly well explained in the existing docs.  I tried
> to improve the explanation awhile ago in HEAD:
> 
> https://www.postgresql.org/docs/devel/plpgsql-statements.html#PLPGSQL-STATEMENTS-GENERAL-SQL

Oh, I thought he wanted to declare a function inside the function that
could be called only by that function, like private functions in Oracle
packages can do.  Yes, you can create a function that defines a function
that can be called later.  I guess you could also create a function that
_conditionally_ creates a function that it can call itself too.  My
point is that you can't create a function that has function scope ---
they all have schema scope.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  If only the physical world exists, free will is an illusion.




Re: syntax question

From
Marc Millas
Date:
good reading, thanks

Marc MILLAS
Senior Architect
+33607850334



On Thu, Jun 3, 2021 at 9:21 PM Tom Lane <tgl@sss.pgh.pa.us> wrote:
Adrian Klaver <adrian.klaver@aklaver.com> writes:
> On 6/3/21 12:01 PM, Bruce Momjian wrote:
>> On Thu, Jun  3, 2021 at 08:58:03PM +0200, Marc Millas wrote:
>>> within a function, I want to create another function.

>> You can't create functions inside of functions;  same for procedures.

> Sure you can:

Yeah.  The actual problem here is that Marc is expecting variable
substitution to occur within a utility (DDL) statement, which it
doesn't.  The workaround is to build the command as a string and
use EXECUTE, as Adrian illustrated:

> EXECUTE  'create function ' ||  bidule || '() RETURNS void language
> plpgsql AS $fnc$ BEGIN END; $fnc$ ';

This is not terribly well explained in the existing docs.  I tried
to improve the explanation awhile ago in HEAD:

https://www.postgresql.org/docs/devel/plpgsql-statements.html#PLPGSQL-STATEMENTS-GENERAL-SQL

                        regards, tom lane

Re: syntax question

From
Marc Millas
Date:
thanks Adrian, exactly what I was missing :-)

about knowing if I should...
We have to create a set of triggers (insert, update, delete) within a huge set of tables. and that list of tables, and structure of them  can be customized, maintained, ...
so we were looking for a standard script to automatize the building of the whole thing, taking list of columns  and constraints (for PK) directly from pg_catalog.
Now it works :-)

but.. why do you ask that question ? is there any king of hidden wolf we didnt see ?


Marc MILLAS
Senior Architect
+33607850334



On Thu, Jun 3, 2021 at 9:11 PM Adrian Klaver <adrian.klaver@aklaver.com> wrote:
On 6/3/21 12:01 PM, Bruce Momjian wrote:
> On Thu, Jun  3, 2021 at 08:58:03PM +0200, Marc Millas wrote:
>> Hi,
>>
>> within a function, I want to create another function.
>> no pb.
>> but if I write:
>> declare bidule text;
>> begin
>> bidule:='myfunc';
>> create function bidule() ...
>>
>>
>> it does create a function named bidule and not myfunc.
>> so I am obviously missing something too obvious.
>
> You can't create functions inside of functions;  same for procedures.
>

Sure you can:

CREATE OR REPLACE FUNCTION public.test_fnc()
  RETURNS void
  LANGUAGE plpgsql
AS $function$
DECLARE
      bidule text;
BEGIN
bidule:='myfunc';
EXECUTE  'create function ' ||  bidule || '() RETURNS void language
plpgsql AS $fnc$ BEGIN END; $fnc$ ';
END;


$function$

select test_fnc();
  test_fnc
----------

  \df myfunc
                         List of functions
  Schema |  Name  | Result data type | Argument data types | Type
--------+--------+------------------+---------------------+------
  public | myfunc | void             |                     | func


Whether you should is another question.


--
Adrian Klaver
adrian.klaver@aklaver.com

Re: syntax question

From
"David G. Johnston"
Date:
On Thu, Jun 3, 2021 at 1:02 PM Marc Millas <marc.millas@mokadb.com> wrote:
about knowing if I should...
We have to create a set of triggers (insert, update, delete) within a huge set of tables. and that list of tables, and structure of them  can be customized, maintained, ...
so we were looking for a standard script to automatize the building of the whole thing, taking list of columns  and constraints (for PK) directly from pg_catalog.
Now it works :-)

but.. why do you ask that question ? is there any king of hidden wolf we didnt see ?

Having done this (building a - limited - code generator framework using bash+psql+plpgsql) I will say that doing so using pl/pgsql, while appealing from "no extra tooling needed" perspective, doesn't play to pl/pgsql's strengths.  Using a different language to generate SQL script files, which can then be executed, is probably a better way to go - if you have a different language you can build upon (i.e., not a shell scripting language like bash).

In particular, plpgsql nested strings are not fun to work with in any significant volume.

David J.

Re: syntax question

From
Marc Millas
Date:
I take note of this.
thanks

Marc MILLAS
Senior Architect
+33607850334



On Thu, Jun 3, 2021 at 10:23 PM David G. Johnston <david.g.johnston@gmail.com> wrote:
On Thu, Jun 3, 2021 at 1:02 PM Marc Millas <marc.millas@mokadb.com> wrote:
about knowing if I should...
We have to create a set of triggers (insert, update, delete) within a huge set of tables. and that list of tables, and structure of them  can be customized, maintained, ...
so we were looking for a standard script to automatize the building of the whole thing, taking list of columns  and constraints (for PK) directly from pg_catalog.
Now it works :-)

but.. why do you ask that question ? is there any king of hidden wolf we didnt see ?

Having done this (building a - limited - code generator framework using bash+psql+plpgsql) I will say that doing so using pl/pgsql, while appealing from "no extra tooling needed" perspective, doesn't play to pl/pgsql's strengths.  Using a different language to generate SQL script files, which can then be executed, is probably a better way to go - if you have a different language you can build upon (i.e., not a shell scripting language like bash).

In particular, plpgsql nested strings are not fun to work with in any significant volume.

David J.

Re: syntax question

From
Guyren Howe
Date:
I know it would be non-standard, but I would love to see Postgres support the likes of nested functions.

I know that would be non-standard, but Postgres has lots of non-standard features that make it more like a real programming language and considerably more productive.
On Jun 3, 2021, 12:34 -0700, Bruce Momjian <bruce@momjian.us>, wrote:
On Thu, Jun 3, 2021 at 03:21:15PM -0400, Tom Lane wrote:
Adrian Klaver <adrian.klaver@aklaver.com> writes:
On 6/3/21 12:01 PM, Bruce Momjian wrote:
On Thu, Jun 3, 2021 at 08:58:03PM +0200, Marc Millas wrote:
within a function, I want to create another function.

You can't create functions inside of functions; same for procedures.

Sure you can:

Yeah. The actual problem here is that Marc is expecting variable
substitution to occur within a utility (DDL) statement, which it
doesn't. The workaround is to build the command as a string and
use EXECUTE, as Adrian illustrated:

EXECUTE 'create function ' || bidule || '() RETURNS void language
plpgsql AS $fnc$ BEGIN END; $fnc$ ';

This is not terribly well explained in the existing docs. I tried
to improve the explanation awhile ago in HEAD:

https://www.postgresql.org/docs/devel/plpgsql-statements.html#PLPGSQL-STATEMENTS-GENERAL-SQL

Oh, I thought he wanted to declare a function inside the function that
could be called only by that function, like private functions in Oracle
packages can do. Yes, you can create a function that defines a function
that can be called later. I guess you could also create a function that
_conditionally_ creates a function that it can call itself too. My
point is that you can't create a function that has function scope ---
they all have schema scope.

--
Bruce Momjian <bruce@momjian.us> https://momjian.us
EDB https://enterprisedb.com

If only the physical world exists, free will is an illusion.



Re: syntax question

From
Adrian Klaver
Date:
On 6/3/21 1:01 PM, Marc Millas wrote:
> thanks Adrian, exactly what I was missing :-)
> 
> about knowing if I should...
> We have to create a set of triggers (insert, update, delete) within a 
> huge set of tables. and that list of tables, and structure of them  can 
> be customized, maintained, ...
> so we were looking for a standard script to automatize the building of 
> the whole thing, taking list of columns  and constraints (for PK) 
> directly from pg_catalog.
> Now it works :-)
> 
> but.. why do you ask that question ? is there any king of hidden wolf we 
> didnt see ?

See David Johnston's answer. Nested quoting will drive you to drink(or 
drink more):)


> 
> 
> Marc MILLAS
> Senior Architect
> +33607850334
> www.mokadb.com <http://www.mokadb.com>
> 
> 
> 
> On Thu, Jun 3, 2021 at 9:11 PM Adrian Klaver <adrian.klaver@aklaver.com 
> <mailto:adrian.klaver@aklaver.com>> wrote:
> 
>     On 6/3/21 12:01 PM, Bruce Momjian wrote:
>      > On Thu, Jun  3, 2021 at 08:58:03PM +0200, Marc Millas wrote:
>      >> Hi,
>      >>
>      >> within a function, I want to create another function.
>      >> no pb.
>      >> but if I write:
>      >> declare bidule text;
>      >> begin
>      >> bidule:='myfunc';
>      >> create function bidule() ...
>      >>
>      >>
>      >> it does create a function named bidule and not myfunc.
>      >> so I am obviously missing something too obvious.
>      >
>      > You can't create functions inside of functions;  same for procedures.
>      >
> 
>     Sure you can:
> 
>     CREATE OR REPLACE FUNCTION public.test_fnc()
>        RETURNS void
>        LANGUAGE plpgsql
>     AS $function$
>     DECLARE
>            bidule text;
>     BEGIN
>     bidule:='myfunc';
>     EXECUTE  'create function ' ||  bidule || '() RETURNS void language
>     plpgsql AS $fnc$ BEGIN END; $fnc$ ';
>     END;
> 
> 
>     $function$
> 
>     select test_fnc();
>        test_fnc
>     ----------
> 
>        \df myfunc
>                               List of functions
>        Schema |  Name  | Result data type | Argument data types | Type
>     --------+--------+------------------+---------------------+------
>        public | myfunc | void             |                     | func
> 
> 
>     Whether you should is another question.
> 
> 
>     -- 
>     Adrian Klaver
>     adrian.klaver@aklaver.com <mailto:adrian.klaver@aklaver.com>
> 


-- 
Adrian Klaver
adrian.klaver@aklaver.com



Re: syntax question

From
Marc Millas
Date:
no pb: I am french, so quite skilled on that topic :-)
there is only 50 bottles of various malt on the presentoir close to my desk
so I must stay reasonnable :-)



Marc MILLAS
Senior Architect
+33607850334



On Thu, Jun 3, 2021 at 11:17 PM Adrian Klaver <adrian.klaver@aklaver.com> wrote:
On 6/3/21 1:01 PM, Marc Millas wrote:
> thanks Adrian, exactly what I was missing :-)
>
> about knowing if I should...
> We have to create a set of triggers (insert, update, delete) within a
> huge set of tables. and that list of tables, and structure of them  can
> be customized, maintained, ...
> so we were looking for a standard script to automatize the building of
> the whole thing, taking list of columns  and constraints (for PK)
> directly from pg_catalog.
> Now it works :-)
>
> but.. why do you ask that question ? is there any king of hidden wolf we
> didnt see ?

See David Johnston's answer. Nested quoting will drive you to drink(or
drink more):)


>
>
> Marc MILLAS
> Senior Architect
> +33607850334
> www.mokadb.com <http://www.mokadb.com>
>
>
>
> On Thu, Jun 3, 2021 at 9:11 PM Adrian Klaver <adrian.klaver@aklaver.com
> <mailto:adrian.klaver@aklaver.com>> wrote:
>
>     On 6/3/21 12:01 PM, Bruce Momjian wrote:
>      > On Thu, Jun  3, 2021 at 08:58:03PM +0200, Marc Millas wrote:
>      >> Hi,
>      >>
>      >> within a function, I want to create another function.
>      >> no pb.
>      >> but if I write:
>      >> declare bidule text;
>      >> begin
>      >> bidule:='myfunc';
>      >> create function bidule() ...
>      >>
>      >>
>      >> it does create a function named bidule and not myfunc.
>      >> so I am obviously missing something too obvious.
>      >
>      > You can't create functions inside of functions;  same for procedures.
>      >
>
>     Sure you can:
>
>     CREATE OR REPLACE FUNCTION public.test_fnc()
>        RETURNS void
>        LANGUAGE plpgsql
>     AS $function$
>     DECLARE
>            bidule text;
>     BEGIN
>     bidule:='myfunc';
>     EXECUTE  'create function ' ||  bidule || '() RETURNS void language
>     plpgsql AS $fnc$ BEGIN END; $fnc$ ';
>     END;
>
>
>     $function$
>
>     select test_fnc();
>        test_fnc
>     ----------
>
>        \df myfunc
>                               List of functions
>        Schema |  Name  | Result data type | Argument data types | Type
>     --------+--------+------------------+---------------------+------
>        public | myfunc | void             |                     | func
>
>
>     Whether you should is another question.
>
>
>     --
>     Adrian Klaver
>     adrian.klaver@aklaver.com <mailto:adrian.klaver@aklaver.com>
>


--
Adrian Klaver
adrian.klaver@aklaver.com

inner subprograms ... Was: syntax question

From
Bryn Llewellyn
Date:
bruce@momjian.us wrote:

Oh, I thought he wanted to declare a function inside the function that could be called only by that function, like private functions in Oracle packages can do.  Yes, you can create a function that defines a function that can be called later.  I guess you could also create a function that _conditionally_ creates a function that it can call itself too.  My point is that you can't create a function that has function scope — they all have schema scope.

I’ve heard that EDB’s version of PostgreSQL supports inner subprograms (declared and defined within a DECLARE section) to any depth of nesting—and packages too. Is this true?

I worked at Oracle HQ for the longest time. Not a day goes by, when I need to write PL/pgSQL code, that I don’t miss these two constructs. I wish that (a future version of) vanilla PG could bring support for them.