Re: WARM and indirect indexes

On Tue, Jan 10, 2017 at 11:36:24PM -0300, Alvaro Herrera wrote:
> Bruce Momjian wrote:
>
> > 1. What percentage speedup is the _average_ user going to get? You
> > have to consider people who will use indirect indexes who get no benefit
> > or a net slowdown, and users who will get a benefit.
> >
> > 2. What percentage of users are going to use indirect indexes?
> >
> > So, for #1 you might have users who are getting +1%, +50%, and -20%, so
> > maybe +10% average, and for #2 you might have 0.1%. When you multiply
> > them out, you get 0.01% average improvement per installation, which is
> > very small. Obviously, these are just wild guesses, but this is just to
> > make a point.
>
> Perhaps not many users will require indirect indexes; but for those that
> do, the feature might be invaluable. We don't do only things that
> benefit everybody -- some features are there to satisfy small
> populations ("snapshot too old" is a recent example). We should of
> course do, and perhaps even favor doing things that benefit everybody,
> but should also do the other things.

I never said "We should do only things that benefit everybody," so why
are you saying that? You are arguing against something I didn't say. I
am trying to make a balanced analysis, and you arguing against an
extreme position.

My point is that anything you add must be weighed against the value it
gives to users who use it, and the percentage of users who will use it.
Against that benefit, you have to look at the cost of exposing that API
to users, code complexity, maintenance, etc.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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