Re: BUG #13289: ANY() function produces a paradox

On Thu, May 14, 2015 at 10:01 PM, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
wrote:

> udtelco(at)gmail(dot)com wrote:
> > The following bug has been logged on the website:
> >
> > Bug reference: 13289
> > Logged by: Anton
> > Email address: udtelco(at)gmail(dot)com
> > PostgreSQL version: 9.3.2
> > Operating system: Solaris 11.2
> > Description:
> >
> > select ('2' != any('{2,3}')) , ('2' = any('{2,3}'))
> >
> > When != (or <>) operator is applied to any() , results are wrong.
> Thereby,
> > you have a situation where x = y AND x != y both evaluating as true.
>
> There is no paradox here. When you specify "op ANY array", the operator is
> applied to each element in the array and the whole construct returns
> true if the operator yields true with any of the array elements. 2 != 3
> therefore 2 != any ('{2,3}') is true.
>
> Maybe you want != ALL instead of != ANY. With != ALL, the element would
> be compared to every element and the whole construct would yield true
> only if all the operations yield true.
>

Using de Morgan::

http://en.wikipedia.org/wiki/De_Morgan%27s_laws

(A OR B) => NOT (A OR B) = (NOT A AND NOT B)​
(​x = ANY) => NOT(x = ANY) = (X != ALL)​

ANY = OR; ALL = AND

David J.