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.

Álvaro Herrera      
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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