Re: [xsl] xpath // query

Subject: Re: [xsl] xpath // query
From: "Laura Jenkins" <xsl_list@xxxxxxxxxxx>
Date: Wed, 24 Apr 2002 13:02:47 +0000
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@xxxxxxxxxxxxxxx>
Reply-To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
To: "Xsl-List (E-mail)" <xsl-list@xxxxxxxxxxxxxxxxxxxxxx>
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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