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https://issues.apache.org/jira/browse/HDFS-1287?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12886774#action_12886774
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Scott Carey commented on HDFS-1287:
-----------------------------------
As a general rule, if you need an ordered set or map as a result of an
operation in Java, it is much faster to use a HashMap or HashSet and then order
the results afterwards than to use a TreeMap or TreeSet and iterate. Inserts
are very slow in those data structures. Its even faster still if you can just
use a List for the whole thing. If you have to detect duplicates, probe a Map
or Set before placing into a list then sort the result at the end.
> Why TreeSet is used when collecting block information
> FSDataSet::getBlockReport
> -------------------------------------------------------------------------------
>
> Key: HDFS-1287
> URL: https://issues.apache.org/jira/browse/HDFS-1287
> Project: Hadoop HDFS
> Issue Type: Improvement
> Reporter: NarayanaSwamy
>
> As a return value we are converting this to array and returning and in name
> node also we are iterating ... so can we use list onstead of set. (As the
> block ids are unique, there may not be duplicates)
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