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. Also, your proposed text had a slight mistake: it's not (b=>c) that d' is for, but (a,b=>c). Pushed with those corrections. Thanks for the reports and patches! -- Álvaro Herrera https://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
