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From "A B (JIRA)" <derby-...@db.apache.org>
Subject [jira] Created: (DERBY-1759) XMLSERIALIZE operator doesn't follow SQL/XML spec in some areas when serializing a sequence.
Date Thu, 24 Aug 2006 20:16:50 GMT
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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