XMLSERIALIZE operator doesn't follow SQL/XML spec in some areas when
serializing a sequence.
--------------------------------------------------------------------------------------------
Key: DERBY-1759
URL: http://issues.apache.org/jira/browse/DERBY-1759
Project: Derby
Issue Type: Bug
Affects Versions: 10.2.1.0, 10.2.2.0, 10.3.0.0
Reporter: A B
The SQL/XML specification dictates that, when serializing a sequence of XML
items, the XMLSERIALIZE operator must first "normalize" the sequence based on
the rules defined here:
http://www.w3.org/TR/xslt-xquery-serialization/#serdm
The current Derby implementation doesn't perform such normalization, which
leads to two ways in which the results of an XMLSERIALIZE operator may not
agree with the required behavior:
1. Sequences of atomic values will not have spaces between, but
the space is required as part of step 3 of the normalization
rules at the above link.
2. Derby will allow serialization of a sequence even if it has
a top-level Attribute node in it, but the rules of normalization
dictate that an error should be thrown instead (step 7).
Both of these behaviors can be seen with the following query.
values
xmlserialize(
xmlquery('/ageinfo/@*' passing by ref
xmlparse(
document '<ageinfo age="48" birthdate="1900-02-08"/>'
preserve whitespace
)
empty on empty
)
as char(50)
)
Derby will currently return the following result from this statement:
1
--------------------------------------------------
481900-02-08
This result does not abide by SQL/XML specification because a) Derby allowed
serialization of a sequence having a top-level attribute node (actually, the
sequence had two), and b) the atomic values produced from the attributes were
displayed without a space between them.
The correct behavior for the above example is to return a serialization error
caused by the presence of an Attribute node in the sequence.
If the example was rewritten as, say:
- xmlquery('/ageinfo/@*' passing by ref
+ xmlquery('fn:data(/ageinfo/@*)' passing by ref
then the attribute nodes are no longer present--we only have their atomic
values, which is allowed. Thus the correct result should then be:
1
--------------------------------------------------
48 1900-02-08
Note, though, that Xalan doesn't appear to support the "fn:data" function, so
this rewritten query won't actually work. I tried using Xalan's built-in
string function, as follows:
- xmlquery('/ageinfo/@*' passing by ref
+ xmlquery('string(/ageinfo/@*)' passing by ref
but Xalan only returns the first attribute in that case; it doesn't return the
second one. So part of this Jira issue is probably going to involve figuring
out how to allow a user to retrieve a sequence of attribute *values* (as
opposed to attribute nodes) using Xalan and still abide by the SQL/XML rules.
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