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https://issues.apache.org/jira/browse/HDFS-8555?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15046696#comment-15046696
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amit sehgal commented on HDFS-8555:
-----------------------------------
This is more for adding an additional wrapper over Namenode to keep track of
data kept in each block through indexes e.g. making Namenode intelligent and
data aware. Namenode when requested can give you only those blocks which belong
to Nicholas out of a given large block.
> Random read support on HDFS files using Indexed Namenode feature
> ----------------------------------------------------------------
>
> Key: HDFS-8555
> URL: https://issues.apache.org/jira/browse/HDFS-8555
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: hdfs-client, namenode
> Affects Versions: 2.5.2
> Environment: Linux
> Reporter: amit sehgal
> Assignee: amit sehgal
> Fix For: 3.0.0
>
> Original Estimate: 720h
> Remaining Estimate: 720h
>
> Currently Namenode does not provide support to do random reads. With so many
> tools built on top of HDFS solving the use case of Exploratory BI and
> providing SQL over HDFS. The need of hour is to reduce the number of blocks
> read for a Random read.
> E.g. extracting say 10 lines worth of information out of 100GB files should
> be reading only those block which can potentially have those 10 lines.
> This can be achieved by adding a tagging feature per block in name node, each
> block written to HDFS will have tags associated to it stored in index.
> Namednode when access via the Indexing feature will use this index native to
> reduce the no. of block returned to the client.
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