BUG #5534: IS DOCUMENT predicate errors instead of returning false

Quoting Mike Fowler <mike@mlfowler.com>:

The following bug has been logged online:

Bug reference: 5534
Logged by: Mike Fowler
Email address: mike@mlfowler.com
PostgreSQL version: 9.0beta2
Operating system: Linux 2.6.31-14-generic #48-Ubuntu SMP
Description: IS DOCUMENT predicate errors instead of returning false
Details:

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've mentioned this on -hackers with message ID
20100701172553.w5vdy1xbocos8g40@www.mlfowler.com

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The attached patch is a very small patch that changes parse_expr.c to
not convert everything to xml. This now means that when passed
malformed XML it will return false instead of throwing an exception.
In my mind this acceptable as I don't see anywhere in the standard
that mandates that:

xmlval IS NOT DOCUMENT == xmlval IS CONTENT

Regards,

--
Mike Fowler
Registered Linux user: 379787

On fre, 2010-07-02 at 14:01 +0100, Mike Fowler wrote:

The attached patch is a very small patch that changes parse_expr.c
to
not convert everything to xml. This now means that when passed
malformed XML it will return false instead of throwing an exception.
In my mind this acceptable as I don't see anywhere in the standard
that mandates that:

xmlval IS NOT DOCUMENT == xmlval IS CONTENT

It says that the declared type of the argument of IS DOCUMENT is XML,
which would be invalidated by your patch.