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 07:25:57 -0700 |
> /*/*/b[1][not(following-sibling::b)] Of course, I meant: /*/*/B[1][not(following-sibling::B)] On Wed, Sep 19, 2012 at 7:24 AM, Dimitre Novatchev <dnovatchev@xxxxxxxxx> wrote: > /*/*/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. -- 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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