Subject: Re: [xsl] following-sibling is evil From: "Dimitre Novatchev dnovatchev@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> Date: Sun, 6 Jul 2014 20:42:58 -0000 |
On Sun, Jul 6, 2014 at 12:39 PM, Michael Kay mike@xxxxxxxxxxxx <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote: >> following-sibling::Book[Title eq $currentAuthor and Genre eq >> $currentGenre][1] > > I can't see why that's obviously more efficient. They look identical to me. The "naive" processor will perform only one and not two passes -- doing both comparisons in a single pass. >> >> or probably even better (as a hint to the optimizer): >> >> exists(head(following-sibling::Book[Title eq $currentAuthor and >> Genre eq $currentGenre])) > > Again, it's still quadratic performance if your evaluate this for every Book. Yes, "more efficient" here is relative to the initial expression, not in big O terms. >> -- 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 ------------------------------------- To achieve the impossible dream, try going to sleep. ------------------------------------- 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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