Subject: Re: [xsl] Which is faster: count(/Document/A/B) eq 1 ... or ... /Document/A/(count(B) eq 1) ? From: Dimitre Novatchev <dnovatchev@xxxxxxxxx> Date: Wed, 19 Sep 2012 07:24:24 -0700 |
/*/*/b[1][not(following-sibling::b)] Cheers, Dimitre On Wed, Sep 19, 2012 at 7:07 AM, David Carlisle <davidc@xxxxxxxxx> wrote: > On 19/09/2012 14:34, Costello, Roger L. wrote: >> >> Is there an XPath expression, besides the ones listed, that is even better >> and faster? > > > > You want to avoid count() as then you are relying on the optimiser to > rewrite it away. If you go count(B) eq 1 then unless the optimiser spots > this it may try to calculate count(B) which would mean processing the full > list of elements. > > B and not(B[2]) > > similarly may be read as evaluating the full list of B elements and then > taking the 2nd but it is much more likely the optimiser detects [2] > predicates to abort the construction of the sequence at the second item. > > David > > > -- > google plus: https:/profiles.google.com/d.p.carlisle > > ________________________________________________________________________ > The Numerical Algorithms Group Ltd is a company registered in England > and Wales with company number 1249803. The registered office is: > Wilkinson House, Jordan Hill Road, Oxford OX2 8DR, United Kingdom. > > This e-mail has been scanned for all viruses by Star. The service is > powered by MessageLabs. > ________________________________________________________________________ > -- 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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