https://issues.apache.org/bugzilla/show_bug.cgi?id=52834
Bug #: 52834
Summary: ColumnHelper.getColumnWidth does not scale to large
numbers of rows, with large numbers of merged regions
Product: POI
Version: 3.7
Platform: PC
Status: NEW
Severity: normal
Priority: P2
Component: XSSF
AssignedTo: [email protected]
ReportedBy: [email protected]
Classification: Unclassified
Created attachment 28423
--> https://issues.apache.org/bugzilla/attachment.cgi?id=28423
Patch to resolve issue against http://svn.apache.org/repos/asf/poi/tags/REL_3_7
Attempting to run ColumnHelper.getColumnWidth on a large worksheet (>110,000
rows) with a large number of merged regions (>40,000) runs for a very long time
(ran for an entire weekend before it was noticed and aborted).
This method contains a loop across merged regions nested within a loop across
rows, and several substantial methods are being called within the inner loop,
possibly on the order of a billion times in my example.
However, many of these time-consuming calls are retrieving static data in the
context of this method, so the code can be refactored such that they're only
run once (or once per row), and the results cached. The main problem calls are:
getNumMergedRegions()
getMergedRegion(i)
getRowNum()
With the code refactored thusly, the method ran within a few minutes.
A patch is attached with these suggested changes. The patch is based on the
REL_3_7 tag.
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