syntax question

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.

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

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

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.

good reading, thanks

Marc MILLAS
Senior Architect
+33607850334
www.mokadb.com

On Thu, Jun 3, 2021 at 9:21 PM Tom Lane <tgl@sss.pgh.pa.us> 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 ?

Marc MILLAS
Senior Architect
+33607850334
www.mokadb.com

On Thu, Jun 3, 2021 at 9:11 PM Adrian Klaver <adrian.klaver@aklaver.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.

I take note of this.
thanks

Marc MILLAS
Senior Architect
+33607850334
www.mokadb.com

On Thu, Jun 3, 2021 at 10:23 PM David G. Johnston <
david.g.johnston@gmail.com> wrote:

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 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&gt;

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

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
www.mokadb.com

On Thu, Jun 3, 2021 at 11:17 PM Adrian Klaver <adrian.klaver@aklaver.com>
wrote:

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.