Finding Specific Descendant Nodes With XSL:Key

Question

Given the following code:

<database>
    <table name="table1">
       <column name="id"/>
       <column name="created_at"/>
    </table>
    <table name="table2">
       <column name="id"/>
       <column name="updated_at"/>
    </table>
</database>

I want to be able to test using an xsl:key if specific table has a specific column by name. For instance, I want to know if a table has a 'created_at' column so I can write specific code within the transformation.

I've gotten a general key that will test if any table has a given column by name, but have not figured out how to make it specific to the table the transformation is currently working with.

    <xsl:key name="columnTest" match="column" use="@name"/>
 <xsl:for-each select="database/table">   
    <xsl:choose>
       <xsl:when test="key('columnTest', 'created_at')">
          <xsl:text>true</xsl:text>
       </xsl:when>
       <xsl:otherwise>
          <xsl:text>false</xsl:text>
       </xsl:otherwise>
    </xsl:choose>
</xsl:for-each>

So I end up with 'true' for all the tables. Any guidance would be appreciated.

Answer 1

The following transformation shows how this can be done:

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform"&gt;

 <xsl:output method="text"/>

 <xsl:key name="kTableByName"
  match="table" use="@name"/>

 <xsl:key name="kColumnByTable"
  match="column" use="concat(generate-id(..), '+', @name)"/>

 <xsl:template match="/">
  <xsl:value-of select=
   "boolean(key('kColumnByTable',
                 concat(generate-id(key('kTableByName', 'table1')),
                        '+',
                        'created_at'
                       )
               )
            )
   "/>

  <xsl:text>&#xA;</xsl:text>

  <xsl:value-of select=
   "boolean(key('kColumnByTable',
                 concat(generate-id(key('kTableByName', 'table1')),
                        '+',
                        'updated_at'
                       )
               )
            )
   "/>
 </xsl:template>
</xsl:stylesheet>

When this transformation is applied on the provided XML document, the wanted, correct result is produced:

true
false