Re: [xsl] Optimizing preceding-sibling & following-sibling axes (with key()?)

[Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>]

Martynas,

You could work with a key defined like this:

<xsl:key name="headers-with" match="h6" use="generate-id(preceding-sibling::*
  [self::h5|self::h4|self::h3|self::h2|self::h1][1])"/>

<xsl:key name="headers-with" match="h5" use="generate-id(preceding-sibling::*
  [self::h4|self::h3|self::h2|self::h1][1])"/>

<xsl:key name="headers-with" match="h4" use="generate-id(preceding-sibling::*
  [self::h3|self::h2|self::h1][1])"/>

<xsl:key name="headers-with" match="h3" use="generate-id(preceding-sibling::*
  [self::h2|self::h1][1])"/>

<xsl:key name="headers-with" match="h2" 
use="generate-id(preceding-sibling::h1[1])"/>

Calling key('headers-with',generate-id(.)) will then get you all the 
headers that belong to the current node, if it's an h1-h5.

I can't speak for how fast the indexes would be to build -- in 
general, flat data sets present the potential for problems no matter 
what -- but they should be plenty fast to use.

Cheers,
Wendell

At 02:56 PM 4/7/2010, you wrote:
> Hey,
>
> I have such a variable definition (quite cumbersome):
>
> <xsl:variable name="descendant-headings"
> select="following-sibling::h:*[self::h:h1 or self::h:h2 or self::h:h3
> or self::h:h4 or self::h:h5 or self::h:h6][o2e:heading-level(.) &gt;
> o2e:heading-level(current())][preceding-sibling::h:*[self::h:h1 or
> self::h:h2 or self::h:h3 or self::h:h4 or self::h:h5 or
> self::h:h6][o2e:heading-level(.) = o2e:heading-level(current())][1] is
> current()]"/>
>
> Basically, I need to select all descendant (level-wise, not as in
> descendant axis) headings for the current() one, meaning all following
> headings with lower level which go before the next heading one the
> same level as current(). This expression gives me what I need.
> o2e:heading-level() function simply extracts the level number from
> elements name, like 'h3'.
>
> Now, I've read multiple times that preceding-sibling/following-sibling
> are slow. I wonder if this expression could be optimized?
> I also have a key definition which I use for similar purposes:
>
> <xsl:key name="heading-by-level" match="h:h1 | h:h2 | h:h3 | h:h4 |
> h:h5 | h:h6" use="number(substring-after(local-name(), 'h'))"/>
>
> I just can't figure out how combine this key with the sibling axes to
> get the same result and improve performance, i.e. that instead of
> traversing the whole document it would be enough to traverse key()
> values, like in key('heading-by-level', 1 to 6).
> Does it make sense?
>
> Thanks,
>
> Martynas
> odt2epub.com


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Wendell Piez                            mailto:wapiez@xxxxxxxxxxxxxxxx
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