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https://issues.apache.org/jira/browse/XMLBEANS-438?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Bryce Alcock updated XMLBEANS-438:
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Attachment: Main.java
ResponseTimeVsRowCount.png
This is a main Test.
To run it with the xmlbeans (xlsx format) type:
# java poitest.Main true
you may have to modify your classpath.
I can upload an executable jar if that would help.
About the PNG file:
this is an image from excel that shows the results of running the above main
test.
You will see that at the rows increase the processing time/row (red dots)
increase linearly O(n).
This should be a constant time operation.
This causes the total processing time to increase as O(n^2) the blue dots.
> O(n^2) operation in xmlbeans would like to make O(n log n) or better
> --------------------------------------------------------------------
>
> Key: XMLBEANS-438
> URL: https://issues.apache.org/jira/browse/XMLBEANS-438
> Project: XMLBeans
> Issue Type: Improvement
> Affects Versions: Version 2.4
> Environment: Using XMLbeans inside of POI when saving spreadsheets in
> the XLSX file format.
> Reporter: Bryce Alcock
> Attachments: Main.java, ResponseTimeVsRowCount.png
>
>
> Using POI to save a spread sheet in XLSX format causes an O(n^2) operation to
> occur.
> Specifically:
> Just a Quick overview
> it seems like XmlComplexContentImpl.arraySetterHelper iterates over all
> elements in the spread sheet.
> then in side of that iteration, the Xobj.find_element_user(Qname,int) is an
> Order n operation.
> Just making Xobj.find_element_user a O(log n) would completely solve the
> problem.
> ANALYSIS: O(n^2) in XML Beans: (Around Line 1153 or so pf
> XmlComplexContentImpl.java method arraySetterHelper)
> -----------------------------------------------------------
> // Order N (this is invoked 1 time for each element in sources (~120,000
> records in my case)
> for ( i++, j++; i < sources.length; i++, j++)
> {
> long t1 = System.currentTimeMillis();
> XmlCursor c = sources[i].isImmutable() ? null : sources[i].newCursor();
> getCursorTime += (System.currentTimeMillis()-t1);
> long t2=System.currentTimeMillis();
> if (c != null && c.toParent() && c.getObject() == this)
> {
> ifCheckTime += (System.currentTimeMillis()-t2);
> long t3 = System.currentTimeMillis();
> c.dispose();
> long t4 = System.currentTimeMillis();
> // THIS CAUSES O(n^2) SEE CODE BELOW, but this on O(n) for each record.
> // THIS IS THE INEFFICIENCY in XMLBeans...
> current = store.find_element_user( elemName, j );
> findUserElement += (System.currentTimeMillis() - t4);
> if (current == sources[i])
> ; // advance
> else
> {
> // Fall back to the general case
> break;
> }
> insideIfTime += (System.currentTimeMillis()-t3);
> }
> else
> {
> ifCheckTime += (System.currentTimeMillis()-t2);
> c.dispose();
> // Insert before the current element
> TypeStoreUser user = store.insert_element_user( elemName, j );
> ((XmlObjectBase) user).set( sources[i] );
> }
> }
> ---------------- Method from store.find_element_user(QName,int i)---------
> // THIS METHOD IS 0(n)
> // but this is called n times by XmlComplexContentImpl.java around line
> 1153....
> public TypeStoreUser find_element_user ( QName name, int i )
> {
> for ( Xobj x = _firstChild ; x != null ; x = x._nextSibling )
> if (x.isElem() && x._name.equals( name ) && --i < 0)
> return x.getUser();
> return null;
> }
> I will add a sample code showing exactly how to reproduce this issue.
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