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https://issues.apache.org/jira/browse/NUTCH-702?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12713383#action_12713383
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Dmitry Lihachev commented on NUTCH-702:
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I catched NPE when using this patch
{code}
java.lang.NullPointerException
at org.apache.nutch.crawl.CrawlDatum.putAllMetaData(CrawlDatum.java:216)
at org.apache.nutch.crawl.CrawlDbReducer.reduce(CrawlDbReducer.java:134)
at org.apache.nutch.crawl.CrawlDbReducer.reduce(CrawlDbReducer.java:35)
at org.apache.hadoop.mapred.ReduceTask.run(ReduceTask.java:436)
at org.apache.hadoop.mapred.Child.main(Child.java:158)
{code}
at line 216 we can see this part of code
{code}
metaData.put(e.getKey(), e.getValue());
{code}
but metadata is yet not initialized.
I think problem can be soved if change this code part to
{code}
getMetaData().put(e.getKey(), e.getValue());
{code}
> Lazy Instanciation of Metadata in CrawlDatum
> --------------------------------------------
>
> Key: NUTCH-702
> URL: https://issues.apache.org/jira/browse/NUTCH-702
> Project: Nutch
> Issue Type: Improvement
> Affects Versions: 1.0.0
> Reporter: Julien Nioche
> Attachments: NUTCH-702.patch
>
>
> CrawlDatum systematically instanciates its metadata, which is quite wasteful
> especially in the case of CrawlDBReducer when it generates a new CrawlDatum
> for each incoming link before storing it in a List.
> Initial testing on the lazy instanciation shows an improvement in both speed
> and memory consumption. I will generate a patch for it ASAP
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