On Sun, Nov 10, 2024 at 1:14 PM Jim Jones <jim.jo...@uni-muenster.de> wrote: > rebase.
Hmm, this patch has gotten no responses for 4 months. That's kind of unfortunate. Sadly, there's not a whole lot that I can do to better the situation, because I know very little either about XML-related standards or about how people make use of XML in practice. It's not that much code, so if it does a useful thing that we actually want, we can probably figure out how to verify that the code is correct, or fix it. But I don't know whether it's a useful thing that we actually want. Syntactically, XMLCAST() looks a lot like CAST(), so one might ask whether the things that it does can already be accomplished using CAST(); or whether, perhaps, we have some other existing method for performing such conversions. The only thing I found during a quick perusal of the documentation was XMLTABLE(), which seems a bit baroque if you just want to convert one value. Is this intended to plug that gap? Is there any other current way of doing it? Do we need to ensure some kind of consistency between XMLTABLE() and XMLCAST() in terms of how they behave? The documentation at https://www.postgresql.org/docs/current/xml-limits-conformance.html#FUNCTIONS-XML-LIMITS-CASTS says that "When PostgreSQL maps SQL data values to XML (as in xmlelement), or XML to SQL (as in the output columns of xmltable), except for a few cases treated specially, PostgreSQL simply assumes that the XML data type's XPath 1.0 string form will be valid as the text-input form of the SQL datatype, and conversely." Unfortunately, it does not specify what those cases treated specially are, and the commit that added that documentation text is not the one that added the underlying code, so I don't actually know where that code is, but one would expect this function to conform to that general rule. I emphasize again that if there are people other than the submitter who are interested in this patch, they should really chime in. This can't progress in a vacuum. -- Robert Haas EDB: http://www.enterprisedb.com
