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Thread: Re: Access a Field / Column of a resultset by Number

Re: Access a Field / Column of a resultset by Number

From
Daniel Schuchardt
Date:
thats exactly the same i'm looking for:

http://wiki.postgresql.org/wiki/Todo
http://archives.postgresql.org/pgsql-patches/2005-07/msg00458.php

(todo list for plpgsql)

*Server-Side Languages
*PL/pgSQL
*
*[D] Allow listing of record column names, and access to record columns
*via variables, e.g. columns := r.(*), tval2 := r.(colname)
*
*Re: PL/PGSQL: Dynamic Record Introspection


is that is possible in any pl* language?




Daniel Schuchardt schrieb:
> hy group,
>
> i currently look for a solution to access a resultset in a db-stored
> function by number. in plpgsql thats not possible.
> so i checked out plpython. so far so good, thats working:
>
> CREATE OR REPLACE FUNCTION dokv_dorecnokeywords(sqlstatement VARCHAR)
> RETURNS VOID AS
> $$
>  rv = plpy.execute(sqlstatement, 1)
>  |||||->"SELECT * FROM art WHERE ak_nr='TEST'"
>  s  = 'ak_bez'  |||| fieldname is static here, should be by number
>  plpy.notice(s+'='+rv[0][s])
>  return
> $$ LANGUAGE plpythonu;
>
> now i need a solution to get the number of fields as well as the
> fieldnames of that resultset and run through all fields (by number or by
> name). (i need the fieldname too)
>


--
Daniel Schuchardt
/Softwareentwicklung/

/http://www.prodat-sql.de/

Re: Access a Field / Column of a resultset by Number

From
Scott Marlowe
Date:
On Fri, Nov 27, 2009 at 10:09 AM, Daniel Schuchardt
<d.schuchardt@prodat-sql.de> wrote:
> thats exactly the same i'm looking for:
>
> http://wiki.postgresql.org/wiki/Todo
> http://archives.postgresql.org/pgsql-patches/2005-07/msg00458.php
>
> (todo list for plpgsql)
>
> *Server-Side Languages
> *PL/pgSQL
> *
> *[D] Allow listing of record column names, and access to record columns *via
> variables, e.g. columns := r.(*), tval2 := r.(colname)
> *
> *Re: PL/PGSQL: Dynamic Record Introspection
>
>
> is that is possible in any pl* language?

Yes, if the language has the architecture to handle it.  plpgsql
doesn't right now.  pltcl, plperl, and plain old C functions can
examine records and do dynamic stuff with them.  Any attempt at doing
dynamic queries right now in plpgsql leads to madness, or so I've been
told.

Re: Access a Field / Column of a resultset by Number

From
Daniel Schuchardt
Date:
hy scott,  thanks for your awnser.

yes thats clear. but i can't find any sourcecode. the pl* language
doesnt matter, i need that feature only in one function all over my db.

did you have any sourcecode examples?

http://www.postgresql.org/docs/8.4/interactive/plperl-database.html

nothing about how to access a column by fieldname.

daniel

Scott Marlowe schrieb:
> On Fri, Nov 27, 2009 at 10:09 AM, Daniel Schuchardt
> <d.schuchardt@prodat-sql.de> wrote:
>> thats exactly the same i'm looking for:
>>
>> http://wiki.postgresql.org/wiki/Todo
>> http://archives.postgresql.org/pgsql-patches/2005-07/msg00458.php
>>
>> (todo list for plpgsql)
>>
>> *Server-Side Languages
>> *PL/pgSQL
>> *
>> *[D] Allow listing of record column names, and access to record columns *via
>> variables, e.g. columns := r.(*), tval2 := r.(colname)
>> *
>> *Re: PL/PGSQL: Dynamic Record Introspection
>>
>>
>> is that is possible in any pl* language?
>
> Yes, if the language has the architecture to handle it.  plpgsql
> doesn't right now.  pltcl, plperl, and plain old C functions can
> examine records and do dynamic stuff with them.  Any attempt at doing
> dynamic queries right now in plpgsql leads to madness, or so I've been
> told.
>


--
Daniel Schuchardt
/Softwareentwicklung/

/http://www.prodat-sql.de/