Thread: DB2's row_number()

I had a brief look at DB2's row_number function which seems to be pretty 
useful.
What it does is:

test=# SELECT row_number(), relname FROM pg_class LIMIT 3; row_number |    relname
------------+----------------          1 | pg_description          2 | pg_group          3 | pg_proc
(3 rows)

This makes sense to me and I need this feature from time to time. My 
question is: How do I find out when a query starts? Inside a table 
function I can call SRF_IS_FIRSTCALL() to see when it is called first. 
Is there an easy way to check that inside an "ordinary" C function 
returning just one value?
Currently my function counts the number of times it has been called per 
connection. I could write a second function for resetting the counter 
but this is not too smart ...
Regards,
    Hans


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Here is how I doi it when I need to...

BEGIN;
CREATE TEMP SEQUENCE row_num;
SELECT next_val('row_num'), relname FROM pg_class LIMIT 3;
ROLLBACK;

You could also do this with a Set Returning Fucntion so that it returns the
nextval in a simular way



On Thursday 17 July 2003 08:03, Hans-Jürgen Schönig wrote:
> I had a brief look at DB2's row_number function which seems to be pretty
> useful.
> What it does is:
>
> test=# SELECT row_number(), relname FROM pg_class LIMIT 3;
>   row_number |    relname
> ------------+----------------
>            1 | pg_description
>            2 | pg_group
>            3 | pg_proc
> (3 rows)
>
> This makes sense to me and I need this feature from time to time. My
> question is: How do I find out when a query starts? Inside a table
> function I can call SRF_IS_FIRSTCALL() to see when it is called first.
> Is there an easy way to check that inside an "ordinary" C function
> returning just one value?
> Currently my function counts the number of times it has been called per
> connection. I could write a second function for resetting the counter
> but this is not too smart ...
>
>     Regards,
>
>         Hans

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fx:  250.763.1759
http://www.wavefire.com

Hans-Jürgen Schönig <postgres@cybertec.at> writes:
> question is: How do I find out when a query starts? Inside a table 
> function I can call SRF_IS_FIRSTCALL() to see when it is called first. 
> Is there an easy way to check that inside an "ordinary" C function 
> returning just one value?

Use fn_extra to store some state data.
pg_stat_get_backend_idset() is a useful example.
        regards, tom lane