Subject: Re: [xsl] Search for efficiency...(building nodes dynamically) From: "andrew welch" <andrew.j.welch@xxxxxxxxx> Date: Thu, 2 Mar 2006 14:50:56 +0000 |
On 3/2/06, Ahsan Ali <doubleletter@xxxxxxxxx> wrote: > Hi all, > > I have an XML file of 6588 Airport elements as follows: > > <apt code="AAF" city="Apalachicola" country="United States" > state="FL">Municipal Apt.</apt> > .... > > In an XSLT program, I am processing yet another XML document that has > the following format: > > <availabilitytable> > <avail> > <origin>XYZ</origin> > <destination>XYZ</destination> > </avail> > > <avail> > <origin>XYZ</origin> > <destination>XYZ</destination> > </avail> > </availabilitytable> > > These are an approx of 15-20 'avail' elements. > > The problem: I have written the XSL sheet in such a way that for every > 'origin' and 'destination' element, the > <apt> nodeset is traversed to get the airport name of a given code. > > Therefore, if there are duplicate origins/destinations (which is very > probable in my case) there will be unnecessary multiple traversals. > > So I thought of building a nodeset of all origins/destinations, > removing duplicates, and then looking up the <apt> file. > > The Question(s): Since I will need the result node later on in the XSL > file, where do I store it ? And how do I build a result node like this > ? If this is not feasible, what is the best method to avoid multiple > traversals of such a large tree ? Use a key: <xsl:key name="airports-by-code" match="apt" use="@code"/> then in your <origin> and <destination> templates: <xsl:template match="origin"> <xsl:apply-templates select="key('airports-by-code', .)"/> You may have to do a little extra work to change the context to the correct document - this is done differently between XSLT 1.0 or 2.0 but it's pretty trivial either way: For 1.0, you have to change the context node to the airport XML using a for-each, keeping track of the value of the origin node: <xsl:template match="origin"> <xsl:variable name="origin" select="."/> <xsl:for-each select="$airportsDoc"> <xsl:apply-templates select="key('airports-by-code', $origin)"/> For 2.0, you can use the 3rd argument of key() to specify the XML that should keyed into: <xsl:template match="origin"> <xsl:apply-templates select="key('airports-by-code', ., $airportsDoc)"/> Another great feature of 2.0! cheers andrew
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