Quoting Mike Fowler <mike@mlfowler.com>:
> Should the IS DOCUMENT predicate support this? At the moment you get
> the following:
>
> template1=# SELECT
> '<towns><town>Bidford-on-Avon</town><town>Cwmbran</town><town>Bristol</town></towns>'
> IS
> DOCUMENT;
> ?column?
> ----------
> t
> (1 row)
>
> template1=# SELECT
> '<towns><town>Bidford-on-Avon</town><town>Cwmbran</town><town>Bristol</town></towns'
> IS
> DOCUMENT;
> ERROR: invalid XML content
> LINE 1: SELECT '<towns><town>Bidford-on-Avon</town><town>Cwmbran</to...
> ^
> DETAIL: Entity: line 1: parser error : expected '>'
> owns><town>Bidford-on-Avon</town><town>Cwmbran</town><town>Bristol</town></towns
>
> ^
> Entity: line 1: parser error : chunk is not well balanced
> owns><town>Bidford-on-Avon</town><town>Cwmbran</town><town>Bristol</town></towns
>
> ^
> I would've hoped the second would've returned 'f' rather than failing.
> I've had a glance at the XML/SQL standard and I don't see anything in
> the detail of the predicate (8.2) that would specifically prohibit us
> from changing this behavior, unless the common rule 'Parsing a string
> as an XML value' (10.16) must always be in force. I'm no standard
> expert, but IMHO this would be an acceptable change to improve
> usability. What do others think?
Right, I've answered my own question whilst sitting in the open source
coding session at CHAR(10). Yes, IS DOCUMENT should return false for a
non-well formed document, and indeed is coded to do such. However, the
conversion to the xml type which happens before the underlying
xml_is_document function is even called fails and exceptions out. I'll
work on a patch to resolve this behavior such that IS DOCUMENT will
give you the missing 'xml_is_well_formed' function.
Regards,
--
Mike Fowler
Registered Linux user: 379787