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List:       xmlbeans-dev
Subject:    [jira] Commented: (XMLBEANS-438) O(n^2) operation in xmlbeans would
From:       "David Fisher (JIRA)" <xmlbeans-dev () xml ! apache ! org>
Date:       2010-10-13 15:46:34
Message-ID: 32485615.115401286984794197.JavaMail.jira () thor
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    [ https://issues.apache.org/jira/browse/XMLBEANS-438?page=com.atlassian.jira.plugi \
n.system.issuetabpanels:comment-tabpanel&focusedCommentId=12920613#action_12920613 ] 

David Fisher commented on XMLBEANS-438:
---------------------------------------

This is a problem for Apache POI. We would really like to have a solution.

Any comments on array setters and making these efficient?

> 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, PoiTest.jar, 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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