Re: create type with %type or %rowtype

Post Gresql <postgresql@xxxxxxxxxxx> · Wed, 18 Nov 2020 08:34:05 +0100



    On 2020-11-18 04:37, David G. Johnston
      wrote:

    
              (resending
                  to include the list)
              

              On Tue,
                  Nov 17, 2020 at 3:12 PM Post Gresql <postgresql@xxxxxxxxxxx>
                  wrote:

              
              create type my_type
                as my_table%rowtype;

              
              This
                would be redundant with existing behavior - all tables
                have a corresponding type already
            
            
              create type my_type
                as my_table.my_column%type;

              
            What does the indirection get
                  us?
            
               
              Correct? It seems to
                be a feature for plpgsql programing only, right?

              
            Correct
            
              
                But wouldn't that be a good thing to be able to do?
              

              You are
                the one proposing it - why would it be a good thing to
                do?
            
          
    My idea, that I did not explain properly, sorry for that, is that
      when I write plpgsql functions I sometime need to have a certain
      column type as return value, or even a complete table row as
      return type.
    Then it would be great if I could just refer to the column or row
      type when delcaring the return type.
    It would also be handy if I could reference types when declaring
      other types, 

    
    for example
    create type my_type (a int, b my_table.my_column%type);
    

    The real reason: you will be sure you are using the same type
      everywhere.  And it is easier to change type later on, then only
      one column has to be changed, not many and in a lot of different
      places.

    
    I hope that explains my idea.

    
          David
            J.
            

        On Tue, Nov 17, 2020 at 3:12
          PM Post Gresql <postgresql@xxxxxxxxxxx> wrote:

        
        Hello.

          
          It seems that I can not create a type with

          
          create type my_type as my_table%rowtype;

          
          or

          
          create type my_type as my_table.my_column%type;

          
          Correct? It seems to be a feature for plpgsql programing only,
          right?

          
          But wouldn't that be a good thing to be able to do? Or would
          it cause 

          too many problems?

          
          Best regards