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Re: xpath // query


i am making an attempt to answer ur question

select="A//C"
This would make the processor to search for C that are children of A iin the 
whole document.. This is definitely not fast
select="A//B//C"
would make the processor to search for all Cs under all Bs under A.
This is slightly better approach..
But ** If you are sure C is under B and also if you are sure that B is a 
direct child of A then the best would be /A/B//C..

>After thinking for a while, Im guessing it makes no difference to the
>selection time as the same number of nodes still need to be traversed.
>Theoretically, it may be slower as it involves an extra test.  Is this
>correct?  (or too insignificant to worry about)...

I think it does make a difference because the selection would straight away 
points to the Children of B ( with /A//B//C) than going and checking all the 
children of the root element A( with A//C)

hope this helps


>From: "Andrew Welch" <awelch@piper-group.com>
>Reply-To: xsl-list@lists.mulberrytech.com
>To: "Xsl-List (E-mail)" <xsl-list@lists.mulberrytech.com>
>Subject: [xsl] xpath // query
>Date: Wed, 24 Apr 2002 12:34:17 +0100
>
>
>Hi list,
>
>If I know that the element I am looking for will have a two certain
>ancestors, but an unknown number of elements in between, can I improve the
>xpath to reach the element by including the middle element?
>
>For example, is:
>
>select="A//C"
>
>any different to:
>
>select="A//B//C"
>
>when I know that <B> is *guranteed* to be there (both select the same
>nodes).  By adding the test for <B>, will it make the selection any faster?
>
>After thinking for a while, Im guessing it makes no difference to the
>selection time as the same number of nodes still need to be traversed.
>Theoretically, it may be slower as it involves an extra test.  Is this
>correct?  (or too insignificant to worry about)...
>
>cheers
>andrew
>
>
>
>
>
>
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>
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>
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