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From "Ted Yu (JIRA)" <j...@apache.org>
Subject [jira] [Comment Edited] (HBASE-15482) Provide an option to skip calculating block locations for SnapshotInputFormat
Date Fri, 08 Dec 2017 04:45:00 GMT

    [ https://issues.apache.org/jira/browse/HBASE-15482?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16283043#comment-16283043
] 

Ted Yu edited comment on HBASE-15482 at 12/8/17 4:44 AM:
---------------------------------------------------------

{code}
+      List<String> locations = new ArrayList<>(Math.min(numTopsAtMost, hostAndWeights.length));
...
+      for (int i = 1; i < hostAndWeights.length; i++) {
{code}
Shouldn't the value of Math.min() be used as the upper bound of the loop above ?
{code}
+      return locations;
+    } else { // hostAndWeights.length >= 2 && numTopsAtMost >= 2
{code}
nit: you can omit the 'else' keyword following the return in previous if block.


was (Author: yuzhihong@gmail.com):
{code}
+      List<String> locations = new ArrayList<>(Math.min(numTopsAtMost, hostAndWeights.length));
...
+      for (int i = 1; i < hostAndWeights.length; i++) {
{code}
Shouldn't the value of Math.min() be used as the upper bound above ?
{code}
+      return locations;
+    } else { // hostAndWeights.length >= 2 && numTopsAtMost >= 2
{code}
nit: you can omit the 'else' keyword following the return in previous if block.

> Provide an option to skip calculating block locations for SnapshotInputFormat
> -----------------------------------------------------------------------------
>
>                 Key: HBASE-15482
>                 URL: https://issues.apache.org/jira/browse/HBASE-15482
>             Project: HBase
>          Issue Type: Improvement
>          Components: mapreduce
>            Reporter: Liyin Tang
>            Assignee: Xiang Li
>            Priority: Minor
>             Fix For: 2.1.0
>
>         Attachments: HBASE-15482.master.000.patch, HBASE-15482.master.001.patch
>
>
> When a MR job is reading from SnapshotInputFormat, it needs to calculate the splits based
on the block locations in order to get best locality. However, this process may take a long
time for large snapshots. 
> In some setup, the computing layer, Spark, Hive or Presto could run out side of HBase
cluster. In these scenarios, the block locality doesn't matter. Therefore, it will be great
to have an option to skip calculating the block locations for every job. That will super useful
for the Hive/Presto/Spark connectors.



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