Re: Access and Filter Predicate on same execution plan line

No, I'm merely pointing out that your observation of "skip scan is like an index fast full scan" can appear to be true in some cases thanks to recent optimizer changes.
That doesn't affect the way you have to decide column ordering, which should be driven by patterns, frequency, and precision of predicate usage.

Regards
Jonathan Lewis

On Wed, 18 Aug 2021 at 19:35, Mladen Gogala <gogala.mladen_at_gmail.com> wrote:

> Replies in-line
>
> On 8/18/21 8:02 AM, Jonathan Lewis wrote:
> > Not true.
> > But thanks to (relatively) recent changes in the costing of index skip
> > scans it will appear this way if the number of index entries per value
> > of the skipped column(s) is so small that that take less than two
> > blocks (which often means you need 3 or 4 hundred rows per leading
> > values)
>
> Thanks Jonathan! If I understand you correctly, you are advocating
> putting the most selective column in order to avoid an expensive
> operation, not unlike FFS?
>
>
> --
> Mladen Gogala
> Database Consultant
> Tel: (347) 321-1217
> https://dbwhisperer.wordpress.com
>
>

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