Re: RSS Visual Explain index advisor

[Vern Hamberg <vhamberg@xxxxxxxxxxxxxxx>]

The fact that it did no longer advise creating the indexes suggests that 
the optimizer might have used them to determine the best plan. Advising 
an index build does not mean it will always be selected as optimal.

*Regards*

*Vern Hamberg*

IBM Champion 2025 <cid:part1.9Q40OlMh.mEHWK0lc@centurylink.net> CAAC 
(COMMON Americas Advisory Council) IBM Influencer 2023


On 2/12/2026 8:55 AM, Daniel Gross wrote:
> Hi David,
>
> always take the index recommendations with a grain of salt.
>
> It always recommends a lot of indexes, that it will never use, because as you said the "cost" of doing a table scan is sometimes lower than doing an index scan and a table lookup.
>
> Explain is good - and it can really help - but you can do a lot manually by looking up indexes and creating JOIN and WHERE clauses to match them.
>
> HTH
> Daniel
>
>
> > Am 12.02.2026 um 15:39 schrieb David Gibbs via MIDRANGE-L<midrange-l@xxxxxxxxxxxxxxxxxx>:
> >
> > Folks:
> >
> > I'm a bit confused ... I've got a query that performs some joins and record
> > selections.
> >
> > I ran it through visual explain (VE) and reviewed the indexes it
> > recommended.
> >
> > I created those indexes and re-ran VE ... It no longer recommended those
> > indexes, but the diagram it showed remained the same.  It appears that it
> > didn't actually USE the indexes it previously recommended.
> >
> > When I viewed the indexes considered, the newly created indexes had a
> > reason code of 4 because the cost to use the access path was higher than
> > the cost of the chosen access path.
> >
> > Any idea why it would recommend access paths and then disregard them once
> > they exist?
> >
> > Thanks!
> >
> > david
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