On Fri, Jun 23, 2017 at 2:58 AM, Alvaro Herrera <alvhe...@2ndquadrant.com> wrote: > Ashutosh Bapat wrote: >> On Mon, Jun 5, 2017 at 8:22 AM, atorikoshi >> <torikoshi_atsushi...@lab.ntt.co.jp> wrote: >> > Hi, >> > >> > I found below formula to compute selectivities, but >> > I think the last Probability 'P(b=?)' should be 'P(c=?)'. >> > >> >> P(a=?,b=?,c=?) = P(a=?,b=?) * (d + (1-d)*P(b=?)) >> > >> > >> > Attached patch fixes it, and it also adds some spaces >> > following another formula which is on line 86 and >> > computes P(a=?, b=?). >> >> Agree. Also using "d" for "degree of functional dependence (b=>c) as >> well is confusing. We are already using "d" for "degree of functional >> dependence (a=>b). Here' patch to use "d'" instead of "d". > > Since the surrounding text uses single quotes to talk about each letter, > I thought it was better to use a new letter (e) so that we don't require > the "prime" notation, which would end up being either inconsistent, > confusing, stupid-looking, or combinations thereof.
Makes sense. > > Also, your proposed text had a slight mistake: it's not (b=>c) that > d' is for, but (a,b=>c). Sorry for that. > > Pushed with those corrections. Thanks. -- Best Wishes, Ashutosh Bapat EnterpriseDB Corporation The Postgres Database Company -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
