RE: Query/400 to RPG program

[Rob Berendt <rob@xxxxxxxxx>]

Performance is tangential to the original discussion.

The semi original discussion was something like users having trouble figuring 
out the links between files being one of the problems inherent with a query 
tool.  And I mentioned how we should be using join logical files to remedy this 
solution.  Otherwise we'll have to do the same thing as creating a join 
logical, 
only on a PC, when they go with a PC product that was demoed, with the 
appropriate 
join logicals set up.

Actually I should have replied to Steve on this, but I accidentally deleted his 
in 
my morning flood of email.





dshaw@spartan.com on 02/28/2000 11:28:59 AM
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Subject:        RE: Query/400 to RPG program

Steve,

You do realize, of course, that this only applies if the join needs an index
which doesn't already exist?  For example, if you join an order header file to
an order detail file by order number, and if the first field in one or more
indexes of the detail file is order number (which should almost certainly be the
case), then the join will share the already-existing index and not create a new
one.  Sharing an existing index should be the case in most parent-child joins,
so most of these shouldn't add any overhead at file maintenance time, and will
slightly reduce overhead at join usage time.  Many programmers have the notion
that a join logical uses a different kind of index than a normal file, but this
isn't the case - it actually uses the same kind of index that RPG would need for
CHAIN/READE, which more than likely is in the database anyway.

Dave Shaw
Spartan International, Inc.
Spartanburg, SC

> -----Original Message-----
> From: Steve Raisor [mailto:sraisor@earthlink.net]
> 
> At our shop, we don't use joins.  In my opinion, that just hides the
> indexing that goes on behind the scenes and causes a  load on 
> the processor
> for each record that is added to the database.  Instead of 
> indexing the file
> once for each query that is ran, your join is having to index 
> each record
> that is added into your physicals to keep the join logical up to date.
> Depending on whether your files are updated often and the 
> number of queries
> run, this could actually make performance worse overall.
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