Remove duplicate node based on more than one attribute in xml using xslt

Question

I have this input XML which needs to be transformed with an xslt

<root>
    <node id="a">
        <section id="a_1" method="run">
            <item id="0">
                <attribute>
                    <color>Red</color>
                </attribute>
            </item>
        </section>
        <section id="a_2">
            <item id="0">
                <attribute>
                    <color>Red</color>
                </attribute>
            </item>
        </section>
        <section id="a_1" method="run">
            <item id="0">
                <attribute>
                    <color>Red</color>
                </attribute>
            </item>
        </section>
    </node>
    <node id="b">
        <section id="b_1" method="create">
            <user id="b_1a">
                <attribute>
                    <name>John</name>
                </attribute>
            </user>
            <user id="b_1b">
                <attribute>a</attribute>
            </user>
        </section>
        <section id="b_1" method="create">
            <user id="b_1c">
                <attribute>a</attribute>
            </user>
        </section>
        <section id="b_2">
            <user id="b_1a">
                <attribute>
                    <name>John</name>
                </attribute>
            </user>
        </section>
    </node>
</root>

Expected output:

<root>
    <node id="a">
        <section id="a_1">
            <item id="0">
                <attribute>
                    <color>Red</color>
                </attribute>
            </item>
        </section>
        <section id="a_2">
            <item id="0">
                <attribute>
                    <color>Red</color>
                </attribute>
            </item>
        </section>
    </node>
    <node id="b">
        <section id="b_1" method="create">
            <user id="b_1a">
                <attribute>
                    <name>John</name>
                </attribute>
            </user>
            <user id="b_1b">
                <attribute>a</attribute>
            </user>
        </section>

        <section id="b_2">
            <user id="b_1a">
                <attribute>
                    <name>John</name>
                </attribute>
            </user>
        </section>
    </node>
</root>

It does not matter which node will be eliminated, as long as it has the same element name, id and method, one of them will be removed. Any idea what the xsl looks like ?

Note: the element name can be anything doesn't have to be and it has more than one element name in the whole file; as long as it has the same element name, id and attribute (ex. method=create) one of them will be eliminated.

Thanks very much. cheers, John

Dimitre Novatchev · Accepted Answer · 2012-04-22 14:52:15Z

3

I. Here is a short and efficient (using keys) XSLT 1.0 transformation:

<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>
 <xsl:strip-space elements="*"/>

 <xsl:key name="kElemWithAttribs" match="*[@id and @method]"
  use="concat(name(), '+', @id, '+', @method)"/>

 <xsl:template match="node()|@*">
     <xsl:copy>
       <xsl:apply-templates select="node()|@*"/>
     </xsl:copy>
 </xsl:template>

 <xsl:template match=
  "*[@id and @method
    and
     not(generate-id()
        =
         generate-id(key('kElemWithAttribs',
                         concat(name(), '+', @id, '+', @method)
                         )[1]
                    )
         )
     ]"/>
</xsl:stylesheet>

When this transformation is applied on the provided XML document:

<root>
    <node id="a">
        <section id="a_1" method="run">
            <item id="0">
                <attribute>
                    <color>Red</color>
                </attribute>
            </item>
        </section>
        <section id="a_2">
            <item id="0">
                <attribute>
                    <color>Red</color>
                </attribute>
            </item>
        </section>
        <section id="a_1" method="run">
            <item id="0">
                <attribute>
                    <color>Red</color>
                </attribute>
            </item>
        </section>
    </node>
    <node id="b">
        <section id="b_1" method="create">
            <user id="b_1a">
                <attribute>
                    <name>John</name>
                </attribute>
            </user>
            <user id="b_1b">
                <attribute>a</attribute>
            </user>
        </section>
        <section id="b_1" method="create">
            <user id="b_1c">
                <attribute>a</attribute>
            </user>
        </section>
        <section id="b_2">
            <user id="b_1a">
                <attribute>
                    <name>John</name>
                </attribute>
            </user>
        </section>
    </node>
</root>

the wanted, correct result is produced:

<root>
   <node id="a">
      <section id="a_1" method="run">
         <item id="0">
            <attribute>
               <color>Red</color>
            </attribute>
         </item>
      </section>
      <section id="a_2">
         <item id="0">
            <attribute>
               <color>Red</color>
            </attribute>
         </item>
      </section>
   </node>
   <node id="b">
      <section id="b_1" method="create">
         <user id="b_1a">
            <attribute>
               <name>John</name>
            </attribute>
         </user>
         <user id="b_1b">
            <attribute>a</attribute>
         </user>
      </section>
      <section id="b_2">
         <user id="b_1a">
            <attribute>
               <name>John</name>
            </attribute>
         </user>
      </section>
   </node>
</root>

Explanation:

Using the Muenchian method for grouping with a composite key. Here we ignore (delete) every node that isn't the first in a group.

II. XSLT 2.0 solution -- even shorter and not less efficient:

<xsl:stylesheet version="2.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:output omit-xml-declaration="yes" indent="yes"/>

 <xsl:template match="node()|@*">
     <xsl:copy>
       <xsl:apply-templates select="node()|@*"/>
     </xsl:copy>
 </xsl:template>

 <xsl:template match="node">
  <xsl:copy>
    <xsl:apply-templates select="@*"/>

    <xsl:for-each-group select="*"
         group-by="concat(name(), '+', @id, '+', @method)">
      <xsl:apply-templates select="."/>
    </xsl:for-each-group>
  </xsl:copy>
 </xsl:template>
</xsl:stylesheet>

Explanation:

Proper use of xsl:for-each-group with a group-by attribute.

edited Apr 22, 2012 at 14:52

answered Apr 22, 2012 at 14:32

Dimitre Novatchev

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4 Comments

John Over a year ago

just one more thing.. how to fix this code if the removal of duplicate can only occur if it is under the same parents (section id). Thanks.

Dimitre Novatchev Over a year ago

@John: Could you, please, ask a new question -- with a source XML document and a wanted result, and explain the new requirement? Then notify me and I would be glad to answer it.

John Over a year ago

I will post in a few minutes and notify you. Thanks for your time.

John Over a year ago

here is the question stackoverflow.com/questions/10274305/… i apologize if this is very complicated. really have no idea. Thanks once again.

Cylian · Accepted Answer · 2012-04-22 12:30:49Z

1

The XSL file:

<?xml version='1.0'?>
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">

<xsl:template match="/">
    <xsl:apply-templates/>
</xsl:template>

<xsl:template match="root">
    <root>
        <xsl:apply-templates/>
    </root>
</xsl:template>

<xsl:template match="node">
    <node>
        <xsl:copy-of select="@*"/>
        <xsl:apply-templates/>
    </node>
</xsl:template>

<xsl:template match="section[@id = 'b_1'][1]">  
    <section>
        <xsl:copy-of select="node()|@*"/>
    </section>  
</xsl:template>

<xsl:template match="section[@id != 'b_1']">
    <section>       
        <xsl:copy-of select="node()|@*"/>
    </section>
</xsl:template>

<xsl:template match="section[@id = 'b_1'][position() &gt; 1]"/> 

</xsl:stylesheet>

The transformation:

<root>
        <node id="a">
            <section id="a_1">
                <item id="0">
                    <attribute>
                        <color>Red</color>
                    </attribute>
                </item>
            </section>
            <section id="a_2">
                <item id="0">
                    <attribute>
                        <color>Red</color>
                    </attribute>
                </item>
            </section>
        </node>
        <node id="b">
            <section id="b_1" method="create">
                <user id="b_1a">
                    <attribute>
                        <name>John</name>
                    </attribute>
                </user>
                <user id="b_1b">
                    <attribute>a</attribute>
                </user>
            </section>
            <section id="b_2">
                <user id="b_1a">
                    <attribute>
                        <name>John</name>
                    </attribute>
                </user>
            </section>
        </node>
    </root>

Hope this helps.

[EDIT] Try this XSL on the same input file:

<?xml version='1.0'?>
<xsl:stylesheet version="1.0"
 xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
 <xsl:output omit-xml-declaration="yes" indent="yes"/>

    <xsl:template match="/">
        <xsl:apply-templates/>
    </xsl:template>

    <xsl:template match="*[not(@id eq preceding::*[local-name() eq local-name(.)]/@id)]">
        <xsl:element name="{name()}">
            <xsl:copy-of select="node()|@*"/>
        </xsl:element>
    </xsl:template>

</xsl:stylesheet>

and the result:

<root>
  <node id="a">
    <section id="a_1">
      <item id="0">
        <attribute>
          <color>Red</color>
        </attribute>
      </item>
    </section>
    <section id="a_2">
      <item id="0">
        <attribute>
          <color>Red</color>
        </attribute>
      </item>
    </section>
  </node>
  <node id="b">
    <section id="b_1" method="create">
      <user id="b_1a">
        <attribute>
          <name>John</name>
        </attribute>
      </user>
      <user id="b_1b">
        <attribute>a</attribute>
      </user>
    </section>
    <section id="b_1" method="create">
      <user id="b_1c">
        <attribute>a</attribute>
      </user>
    </section>
    <section id="b_2">
      <user id="b_1a">
        <attribute>
          <name>John</name>
        </attribute>
      </user>
    </section>
  </node>
</root>

[/EDIT]

edited Apr 22, 2012 at 12:30

answered Apr 22, 2012 at 8:37

Cylian

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5 Comments

John Over a year ago

thanks for the response, but as I mentioned in the question, we need to remove only 1 duplicated node node both. so in that case we still need to keep <section id="b_1" method="create"> and the corresponding children. Do you mind updating the solutions? Thanks a lot.

John Over a year ago

Thanks @Cylian! Really appreciate that. Just one more thing is it possible to generalize, I mean like it can be any element, does not have to be <section> as long as the element name, id and attributes (method=create) is the same, one of them will be eliminated

Cylian Over a year ago

Which XSLT version you're using?

Cylian Over a year ago

See this post and this

John Over a year ago

it's different that did not have attributes

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