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From bugzi...@apache.org
Subject DO NOT REPLY [Bug 27440] New: - nesting-error in SQLTransformer
Date Thu, 04 Mar 2004 15:10:46 GMT
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http://nagoya.apache.org/bugzilla/show_bug.cgi?id=27440

nesting-error in SQLTransformer

           Summary: nesting-error in SQLTransformer
           Product: Cocoon 2
           Version: Current CVS 2.1
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: Other
         Component: general components
        AssignedTo: dev@cocoon.apache.org
        ReportedBy: pmhahn@titan.lahn.de


What I was looking for was somethink like
  SELECT key FROM a UNION B
    SELECT * FROM a WHERE key
    SELECT * FROM b WHERE key

When nesting multiple <sql:execute-query><sql:query/></sql:execute-query>s
inside a top-level <sql:execute-query>-element, nothing is
done/executed/displayed. This is due to a bug with
SQLTransformer.current_query_index:

Here is the relevant code from SQLTransformer.java:
413:startExecuteQueryElement() {
417:   current_query_index = queries.size();
503:endExecuteQueryElement() {
506:   if (current_query_index == 0) executeQuery(0)
511:   else current_query_index--; // BUG!!!!

Here is a trace of an example to illustrate the bug:
<sql:execure-query>    current_query_index := 0;
  <sql:execute-query>  current_query_index := 1;
  </sql:execute-query> current_query_index := 1-- = 0;
  <sql:execute-query>  current_query_index := 2;
  </sql:execute-query> current_query_index := 2-- = 1;
</sql:execute-query>   current_query_index == 1 != 0 // NO executeQuery(0) 

Analysis of the bug:
* current_query_index is used two-fold:
  1. As an index into the Vector queries to indicate the last query,
  2. As an indicator of nesting-level.
  This only works when each <execute-query> contains at-most one other
<execute-query> element.
* Using current_query_index as an indicator for nesting-level does work for
<1><2><3/></2></1> but not for <1><2/><3/><1>.
* current_query_index is used in conjunction with sql:ancestor-value/@sql:level
to compute the parent query.

Clarification/comment:
A DTD for the current working (linear)queries would look like:
<!ELEMENT execute-query (query,execute-query?)>
A DTD for tree-queries, what I tried, would look like:
<!ELEMENT execute-query (query,execute-query*)>

Bug resolution:
Either document that only the 1st type of queries is allowed or rewrite
SQLTransformer to also allow the 2nd type of queries. Would a patch be accepted
if I would implement type 2?

Further comment:
I found one other posting of a person trying to do the same as I:
http://archives.real-time.com/pipermail/cocoon-users/2003-July/036617.html

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