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<h1>xsl:merge</h1>
<p>The <code>xsl:merge</code> instruction is new in XSLT 3.0, and is first implemented in Saxon-EE 9.4. The purpose
of the instruction is to allow streamed merging of two or more pre-sorted input files, but the current implementation
in Saxon is unstreamed.</p>
<p>Each kind of input source is described in an <code>xsl:merge-source</code> child element of the <code>xsl:merge</code>
instruction; and the instances of that kind of input source are selected in a <code>xsl:merge-input</code> child
of the <code>xsl:merge-source</code> element. The processing to be carried out on each group of input items sharing a value
for the merge key is defined in a <code>xsl:merge-action</code> element.</p>
<p>The following example merges a homogenous collection of log files, each already sorted by timestamp:</p>
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<code>
<xsl:merge>
<xsl:merge-source select="collection('log-collection')">
<xsl:merge-input select="events/event"/>
<xsl:merge-key select="@timestamp" order="ascending"/>
</xsl:merge-source>
<xsl:merge-action>
<xsl:sequence select="current-group()"/>
</xsl:merge-action>
</xsl:merge></code>
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<p>The following example merges two log files with different internal structure:</p>
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<xsl:merge>
<xsl:merge-source select="doc('log1.xml')">
<xsl:merge-input select="transactions/transaction"/>
<xsl:merge-key select="xs:dateTime(@date, @time)" order="ascending"/>
</xsl:merge-source>
<xsl:merge-source select="doc('log2.xml')">
<xsl:merge-input select="eventdata/transfer"/>
<xsl:merge-key select="@timestamp" order="ascending"/>
</xsl:merge-source>
<xsl:merge-action>
<xsl:apply-templates select="current-group()"/>
</xsl:merge-action>
</xsl:merge></code>
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<p>The function <code>current-merge-inputs()</code> is not yet implemented.</p>
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