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XML data type and functions EARLY ACCESS

Synopsis

The XML data type stores Extensible Markup Language (XML) documents. YSQL fully supports the PostgreSQL XML implementation, including:

  • XML data type for storing well-formed XML documents
  • XML construction functions for building XML fragments
  • XPath functions for querying XML documents
  • XML predicates for testing document structure
  • XMLTABLE construct for extracting tabular data from XML
  • XML schema mapping functions for converting between tables and XML

For a comprehensive reference of all XML functions, see the PostgreSQL XML documentation.

Data type specification

type_specification ::= xml

Functions and operators

The following key XML functions are supported:

XML construction

  • xmlcomment(text) : Constructs an XML comment
  • xmlconcat(xml, ...) : Concatenates XML fragments
  • xmlelement(name, ...) : Constructs an XML element
  • xmlattributes(...) : Specifies attributes for an XML element
  • xmlforest(...) : Constructs a forest of XML elements
  • xmlpi(name, text) : Constructs an XML processing instruction
  • xmlroot(xml, ...) : Modifies the root node of an XML document

XML parsing and serialization

  • xmlparse(content | document text) : Parses a text string into XML
  • xmlserialize(content | document xml as type) : Converts XML to text

XPath and XML queries

  • xpath(xpath_expr, xml_doc, [namespaces]) : Evaluates XPath expressions
  • xpath_exists(xpath_expr, xml_doc) : Tests if XPath expression matches
  • xmlexists(xpath_expr PASSING [BY REF] xml_doc) : Alternative XPath test syntax
  • XMLTABLE(...) : Converts XML to tabular form

Aggregation

  • xmlagg(xml [ORDER BY ...]) : Aggregates multiple XML values

Validation

  • xml_is_well_formed(text) : Tests if text is well-formed XML
  • xml_is_well_formed_document(text) : Tests if text is a well-formed XML document
  • xml_is_well_formed_content(text) : Tests if text is well-formed XML content

XML predicates

  • IS DOCUMENT : Tests if XML value is a well-formed document
  • IS NOT DOCUMENT : Tests if XML value is not a document

XML schema mapping

Functions to convert between tables and XML are as follows:

  • table_to_xml(table, nulls, tableforest, targetns)
  • table_to_xmlschema(table, nulls, tableforest, targetns)
  • table_to_xml_and_xmlschema(table, nulls, tableforest, targetns)
  • query_to_xml(query, nulls, tableforest, targetns)
  • query_to_xmlschema(query, nulls, tableforest, targetns)
  • query_to_xml_and_xmlschema(query, nulls, tableforest, targetns)
  • cursor_to_xml(cursor, count, nulls, tableforest, targetns)
  • cursor_to_xmlschema(cursor, nulls, tableforest, targetns)
  • schema_to_xml(schema, nulls, tableforest, targetns)
  • schema_to_xmlschema(schema, nulls, tableforest, targetns)
  • schema_to_xml_and_xmlschema(schema, nulls, tableforest, targetns)

For the full reference and detailed descriptions of all XML functions, see the PostgreSQL XML Functions documentation.

See also

For comprehensive examples and guided tutorials on using XML in YSQL, including:

  • Constructing XML documents
  • Querying XML with XPath
  • Converting between tables and XML
  • Handling namespaces

See XML support in YSQL.