Re: Allowing same cursor name in nested levels

Hi Tom,

While going through few test-cases, I found that we cannot have two opened
cursors with same name even though they are in two different functions. Here
is what I mean:

1. I have two functions func1 and func2.
2. func1 calls func2
3. Both has cursor with same name, say mycursor
4. Somehow I forgot closing it
5. executing func1 throws an error 'cursor "mycursor" already in use'

Is this expected behavior???

I just mingled around the code and later appended a cursor count to the
cursor name to allow same cursor name in nested levels. I have run make
check and didn't find any side-effect other than one expected output change.

PFA, patch for the same.

Please let me know your views / suggestions.

Thanks

Test-case:
===

CREATE OR REPLACE FUNCTION func1() RETURNS void AS $$
DECLARE
res int;
mycursor CURSOR FOR SELECT 'foo';
BEGIN
OPEN mycursor;
SELECT func2() INTO res;
END;
$$ LANGUAGE plpgsql;

CREATE OR REPLACE FUNCTION func2() RETURNS int AS $$
DECLARE
mycursor CURSOR FOR SELECT 'bar';
BEGIN
OPEN mycursor;
return 1;
END;
$$ LANGUAGE plpgsql;

SELECT func1();
ERROR: cursor "mycursor" already in use
CONTEXT: PL/pgSQL function "func2" line 5 at OPEN
SQL statement "SELECT func2()"
PL/pgSQL function "func1" line 7 at SQL statement

--
Jeevan B Chalke
Senior Software Engineer, R&D
EnterpriseDB Corporation
The Enterprise PostgreSQL Company

Phone: +91 20 30589500

Website: www.enterprisedb.com
EnterpriseDB Blog: http://blogs.enterprisedb.com/
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Jeevan Chalke <jeevan(dot)chalke(at)enterprisedb(dot)com> writes:
> 1. I have two functions func1 and func2.
> 2. func1 calls func2
> 3. Both has cursor with same name, say mycursor
> 4. Somehow I forgot closing it
> 5. executing func1 throws an error 'cursor "mycursor" already in use'

> Is this expected behavior???

Yes ... or at least, it's always been like that.

> I just mingled around the code and later appended a cursor count to the
> cursor name to allow same cursor name in nested levels.

That would break code that expects the cursor name to be what it said
it should be. It is documented that you can refer to cursors by name
across multiple functions.

regards, tom lane

On Tue, Aug 16, 2011 at 7:25 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Jeevan Chalke <jeevan(dot)chalke(at)enterprisedb(dot)com> writes:
> > 1. I have two functions func1 and func2.
> > 2. func1 calls func2
> > 3. Both has cursor with same name, say mycursor
> > 4. Somehow I forgot closing it
> > 5. executing func1 throws an error 'cursor "mycursor" already in use'
>
> > Is this expected behavior???
>
> Yes ... or at least, it's always been like that.
>
> > I just mingled around the code and later appended a cursor count to the
> > cursor name to allow same cursor name in nested levels.
>
> That would break code that expects the cursor name to be what it said
> it should be. It is documented that you can refer to cursors by name
> across multiple functions.
>

Hmm... got it.

Thanks for the clarification.

>
> regards, tom lane
>

--
Jeevan B Chalke
Senior Software Engineer, R&D
EnterpriseDB Corporation
The Enterprise PostgreSQL Company

Phone: +91 20 30589500

Website: www.enterprisedb.com
EnterpriseDB Blog: http://blogs.enterprisedb.com/
Follow us on Twitter: http://www.twitter.com/enterprisedb

This e-mail message (and any attachment) is intended for the use of the
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