Subject: Re: [xsl] [Summary] Three ways to express in XPath that there are no duplicates in a list of items From: Dimitre Novatchev <dnovatchev@xxxxxxxxx> Date: Fri, 2 Nov 2012 07:25:12 -0700 |
On Fri, Nov 2, 2012 at 6:30 AM, Michael Kay <mike@xxxxxxxxxxxx> wrote: > In some circumstances it would work in the form > > not(//Websites/*[count(distinct-values(//Websites/*))+1]) Yes, this is what I meant -- thank's for the correction. > > But that solution is more dependent on a smart optimizer than the original, > because a naive engine will reevaluate the predicate once for every node > selected; and the performance of an unoptimized implementation of the > original is still (almost) linear, whereas an unoptimized implementation of > the latter is quadratic. I believe that it we re-write this in a more specific form then it wouldn't be so optimizer specific: not(//Websites/*[position() = count(distinct-values(//Websites/*))+1]) or does this require the same degree of cleverness than the previous expression does? Or probably this is even more specific: not(//Websites/*[position() gt count(distinct-values(//Websites/*))]) -- Cheers, Dimitre Novatchev --------------------------------------- Truly great madness cannot be achieved without significant intelligence. --------------------------------------- To invent, you need a good imagination and a pile of junk ------------------------------------- Never fight an inanimate object ------------------------------------- To avoid situations in which you might make mistakes may be the biggest mistake of all ------------------------------------ Quality means doing it right when no one is looking. ------------------------------------- You've achieved success in your field when you don't know whether what you're doing is work or play ------------------------------------- Facts do not cease to exist because they are ignored. ------------------------------------- Typing monkeys will write all Shakespeare's works in 200yrs.Will they write all patents, too? :) ------------------------------------- I finally figured out the only reason to be alive is to enjoy it.
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