On 23 April 2017 at 09:17, Dean Rasheed <dean.a.rash...@gmail.com> wrote:
> On 23 April 2017 at 03:37, Bruce Momjian <br...@momjian.us> wrote:
>> In looking at the new multi-column statistics "dependency" option in
>> Postgres 10, I am quite confused by the term "dependency".  Wouldn't
>> "correlation" be clearer and less confusing as "column dependency"
>> already means something else.

I also asked that exactly that question...

> Actually, the terms "dependency" and "correlation" are both quite
> broad terms that cover a whole range of other different things, and
> hence could be misleading. The precise term for this is "functional
> dependency" [1], so if anything, the option name should be
> "functional_dependencies" or some shortening of that, keeping a part
> of each of those words.

...and got that answer also.

For us "functional dependency" would sound like something to do with
functions (e.g. CREATE FUNCTION), so just "dependency" appears to me
to be the best term for this.

There are multiple statistics for dependency stored, hence
"dependencies". I don't like it, but its the best term I can see at

Simon Riggs                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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