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xPath/HTML: Select node based on related node

Answer 1

A:

I would have left Xpath aside... since I assume it was DOM parsed, I'd use a Map data structure, and match the nodes in either client side or server side (JavaScript / Java) manually.

Seems to me XPath is being streatched beyond its limit here.

Ehrann Mehdan 2009-12-28 09:32:42

I still think XPath is not the best solution here, voting down won't change my mind... or the facts...

Ehrann Mehdan 2009-12-28 19:26:14

I understand and appreciate your comment.. What I am looking for is the most efficient method using xPath.. I can then perform real world benchmarks in my environment using all available options (xPath, java, javascript, etc..) to settle on a final solution.. Thanks for your comment..

chameleon95 2009-12-29 00:59:55

Answer 2

+2 A:

It is possible to use relative paths inside count()
I have never heard of another way to find the node number...

Here is the code with relative xpath-code inside count()

/html/body/table/tr/td[count(../../tr/th[text()='HeaderC']/preceding-sibling::*)+1]

But well, it is not much shorter... It won't be shorter than this in my opinion:

//td[count(../..//th[text()='HeaderC']/preceding-sibling::*)+1]

Harmen 2009-12-28 10:35:26

Excellent.. I am not so much looking for the shortest way to write the expression.. but the most efficient, to minimise the internal lookups..

chameleon95 2009-12-28 14:20:34

Answer 3

A:

Perhaps you want position() and XPath axes?

mst 2009-12-28 16:30:05

Answer 4

A:

Harmen's answer is exactly what you need for a pure XPATH solution.

If you are really concerned with performance, then you could define an XSLT key:

<xsl:key name="columns" match="/html/body/table/tr/th" use="text()"/>

and then use the key in your predicate filter:

/html/body/table/tr/td[count(key('columns', 'HeaderC')/preceding-sibling::th)+1]

However, I suspect you probably won't be able to see a measurable difference in performance unless you need to filter on columns a lot (e.g. for-each loops with checks for every row for a really large document).

Mads Hansen 2009-12-28 19:22:00

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xPath/HTML: Select node based on related node

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