RE: CHAIN Versus SETLL and READ When Data Needed

I prefer to avoid %KDS as well as KLIST....i love the inline keys... 


Thanks,
Tommy Holden


-----Original Message-----
From: rpg400-l-bounces@xxxxxxxxxxxx
[mailto:rpg400-l-bounces@xxxxxxxxxxxx] On Behalf Of Barbara Morris
Sent: Wednesday, February 28, 2007 6:55 PM
To: rpg400-l@xxxxxxxxxxxx
Subject: Re: CHAIN Versus SETLL and READ When Data Needed

Shannon O'Donnell wrote:

              Key1    Klist
                          Kfld              Fld1
                          Kfld              Fld2
                          Kfld              Fld3
              Key2     Klist
                          Kfld              Fld1
                          Kfld              Fld2

CHAIN does seem better if you are always going use the data from a found

record.  But don't take my opinion too seriously because I'm not expert 
in the database; maybe there are scenarios (such as sparse keys) where 
SETLL is faster than CHAIN (or vice versa) when the record is not found.

  (Although a later post in this thread quotes from the manual saying 
that sometimes a CHAIN is faster than a SETLL with sparse keys ...)

Aside from the CHAIN vs SETLL issue, you can improve your key lists by 
using a key data structure, and then using %KDS(keyds:3) or 2 or 1.  (It

would be more self-documenting than the KLISTs, even aside from your 
somewhat devious use of Key1 as the name for the 3-key klist and Key3 as

the name for the 1-key klist :)  You could use a list of keyfields like 
Dennis suggested; but I think the keyds is _slightly_ better than a list

of keyfields _in this case_, since it's a bit easier to see that the 
same key ds is being used for each CHAIN in the group (only one name to 
check vs a list of 3 names or values).

D keyds         e ds        extname(file:*key)
  /free
    keyds.fld1 = something;
    keyds.fld2 = somethingelse;
    keyds.fld3 = whatever;
    chain %kds(keyds:3) file;
    if %found
       ...
    else;
       chain %kds(keyds:2) file;
       if %found
           ...
       else;
          chain %kds(keyds:1) file;