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From: Wolf Guddat <guddat@faps.uni-erlangen.de>
Subject: 3 Quests
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To: postgres@postgres.berkeley.edu
Date: Tue, 17 Aug 93 15:03:29 MESZ
Mailer: Elm [revision: 70.30]

Hi Everybody,

I've got some questions concering some statements in the 
manual which i think do not work as they sould.

Q1: "Each new class name is automatically created as a type"

     I'm not able to create a class which has an attribute of such
     a complex type. (e.g MYCLASS (att1=ANOTHERCLASS) )
     Does this mean this feature is not available. If so why isn't it
     mentioned somewhere?

Q2: Using attributes of type "postquel"

    I know that this isn't running now. I read some short message about
    regproc. What's in detail is it? If i define a postquel-function
    MYFUNCTION and after that create a class 
      MYCLASS (fct=regproc)
    i can do appends like this:
      append MYCLASS (fct = "MYFUNCTION")
    But how can i invoke the execution of the postquel-function when retrieving
    the attribute MYCLASS.fct
      retrieve (MYCLASS.fct) 
    only returns "MYFUNCTION" and doesn't execute it. 
    I was not able to find some detailed information about regproc.

Q3: If i do an append to a class and i do not specify all attributes then 
    these attributes do not have a value (the monitor tells me "(null)").
    Is it possible to return this special "null-value" from 
    a user defined function and how is it implemented? I will need this
    feature for implementing OPTIONAL data-types.

I would be glad to hear from everyone who has a little experiences with one
of this questions.  

Thanks Wolf


*****************************************************
**                                                 **
**                  Wolf Guddat                    **
**                                                 **
**       guddat@faber.faps.uni-erlangen.de         **
**   wfguddat@faui63.informatik.uni-erlangen.de    **
**                                                 **
**       University of Erlangen/Nuernberg          **
**                     Germany                     **
**                                                 **
**     Postgres 4.1, DECstation, ULTRIX 4.3        **
**                                                 **
*****************************************************