XSLT2.0:如何使用嵌套的for-each-group来压缩xml记录

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

  <xsl:template match="/">
    <xsl:for-each-group select="root/record" group-by="field1">
      <xsl:element name="compressedRecord">
        <xsl:attribute name="field1">
          <xsl:value-of select="current-grouping-key()"/>
        </xsl:attribute>
        <xsl:for-each-group select="current-group()" group-by="field2">
          <xsl:element name="subRecord">
            <xsl:attribute name="field2">
              <xsl:value-of select="current-grouping-key()"/>
            </xsl:attribute>
            <xsl:apply-templates select="current-group()"/>
          </xsl:element>
        </xsl:for-each-group>
      </xsl:element>
    </xsl:for-each-group>
  </xsl:template>

  <xsl:template match="record">
    <!-- 处理每个记录的具体逻辑 -->
  </xsl:template>

</xsl:stylesheet>