• Subject: RE: Query Optimizer
  • From: Scott Mildenberger <Smildenber@xxxxxxxxxxxx>
  • Date: Thu, 4 Nov 1999 12:36:07 -0700

I'm not sure why the optimizer chose what it did, one guess might be that
maybe the access path maintenance wasn't set to *immed so it wasn't current.
But I do know one thing, if you create a logical file that can reuse an
existing access path it is built almost immediately.  If the temporary
access path that the optimizer built exactly matched the existing LF then it
would have been built in a very short time.  I'm assuming since you asked
the question that this temporary index took some time to build.  If that is
the case then there must have been something different between the temporary
index and the existing LF.  Not sure this helps but you may want to look at
all the attributes of the existing LF.

Scott Mildenberger

> -----Original Message-----
> From: Pete Hall [SMTP:pbhall@execpc.com]
> Sent: Wednesday, November 03, 1999 6:12 PM
> To:   MIDRANGE-L@midrange.com
> Subject:      Query Optimizer
> Does anyone have a clue as to why the query optimizer would chose to build
> a temporary access path with a key that exactly matches the second of two 
> logical files (no includes or omits)? The explanation says that "The cost 
> to use this access path, as determined by the optimizer, was higher than 
> the cost associated with the chosen access method" (which was to build a 
> temporary index). Does the fact that this is a logical file (DDS) as 
> opposed to and SQL index have any bearing on the matter? This is at V4R3, 
> current on database PTFs.
> Pete Hall
> pbhall@execpc.com
> http://www.execpc.com/~pbhall
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