Just in keeping anyone interested in-tune to what I am finding:
(Slowly plodding forward)
The Code from xmlbeans (XmlComplexContentImpl.java)
has a tight loop, that scales as O(n) for a single match,
and the way XMLBeans is being used within POI causes a scaling of
O(n^2) because each row has hits this method.
this is significant.
If This could be re-written to be O(1) or at least O(log n) then
POI would scale linearly (or log linearly) with spreadsheet size.
We may need to engage the XMLBean folks on this matter.
OR SOMEONE with a really strong algorithms background...
Please let me know if we can figure out how to proceed with this:
(I WOULD LIKE TO GET THE BEST PEOPLE ENGAGED as I think this could
have a significant impact on POI's usability)
CODE: STARTING at Line 1137 of
org.apache.xmlbeans.impl.values.XmlComplexContentImpl.java
-------------------------------------------------------------------------------------------
// The new object matches what already exists in the array
// Heuristic: we optimize for the case where the new elements
// in the array are the same as the existing elements with
// potentially new elements inserted
// First insert the new element in the array at position 0
int j = 0;
for ( j = 0; j < i; j++ )
{
TypeStoreUser user = store.insert_element_user( elemName, j
);
((XmlObjectBase) user).set( sources[j] );
}
for ( i++, j++; i < sources.length; i++, j++)
{
XmlCursor c = sources[i].isImmutable() ? null :
sources[i].newCursor();
if (c != null && c.toParent() && c.getObject() == this)
{
c.dispose();
current = store.find_element_user( elemName, j );
if (current == sources[i])
; // advance
else
{
// Fall back to the general case
break;
}
}
else
{
c.dispose();
// Insert before the current element
TypeStoreUser user = store.insert_element_user(
elemName, j );
((XmlObjectBase) user).set( sources[i] );
}
}
startDest = j;
startSrc = i;
m = store.count_elements( elemName );
}
// Fall through
}
else
{
// All of the elements in the existing array are to
// be deleted and replaced with elements from the
// sources array
}
Thanks
Bryce
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Bryce Alcock * Performance Architect * SunGard *
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http://www.brycealcock.com/
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