On 24.01.25 13:48, Pavel Stehule wrote: > Lot of users use XML functions without XMLDOCUMENT now. The doc should to > help with a reply to question where and when I need (I can) use this > function. This should > be in context of Postgres where every XML expr returns XML value, so > sentence > creates an XML value from XML expression is still very confusing > > What some like > > "SQL/XML introduces XMLDOCUMENT function to returns a document node > from XML tree of some XML value. > This has not any sense (because XML in Postgres is always materialized > to string) in PostgreSQL implementation of XML, and the function just > returns > input value". Or some like that.
I see. I tried to incorporate your suggestion in the text: In the SQL/XML specification, the XMLDocument (X030) function is designed to return a document node from a given XML value expression. Since PostgreSQL handles XML values as materialized strings rather than tree structures, this function does not produce a document node structure but instead returns the validated input <type>xml</type> value as-is. The input <type>xml</type> value can include any valid XML content, such as elements, text, or a mixture of both. This function does not require the input to have a single root element and does not wrap the result in one. Validation of the <type>xml</type> input value depends on the current <xref linkend="guc-xmloption"/> setting. If the input <type>xml</type> value is NULL, the function returns NULL. This function ensures compatibility with the SQL/XML specification, making it particularly useful when migrating SQL queries from other database systems that also implement this standard. Let me know if it is still confusing ... Thanks! Best, Jim
