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https://issues.apache.org/jira/browse/IMPALA-7214?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16766740#comment-16766740
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ASF subversion and git services commented on IMPALA-7214:
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Commit 5b32a0d60110be7c21184819c2dffbb7cbff750f in impala's branch
refs/heads/master from Alex Rodoni
[ https://gitbox.apache.org/repos/asf?p=impala.git;h=5b32a0d ]
IMPALA-7214: [DOCS] More on decoupling impala and DataNodes
Change-Id: I4b6f1c704c1e328af9f0beec73f8b6b61fba992e
Reviewed-on: http://gerrit.cloudera.org:8080/12457
Tested-by: Impala Public Jenkins <[email protected]>
Reviewed-by: Tim Armstrong <[email protected]>
> Update Impala docs to reflect coordinator/executor separation and decoupling
> from DataNodes.
> --------------------------------------------------------------------------------------------
>
> Key: IMPALA-7214
> URL: https://issues.apache.org/jira/browse/IMPALA-7214
> Project: IMPALA
> Issue Type: Bug
> Components: Docs
> Affects Versions: Impala 2.12.0
> Reporter: Tim Armstrong
> Assignee: Alex Rodoni
> Priority: Major
> Fix For: Impala 3.2.0
>
>
> The docs tend to conflate DataNodes (a HDFS service) and Impala daemons. I
> think this stems from the original deployment practice of always colocating
> Impala daemons with HDFS datanodes so that HDFS data could always be read
> from a local DataNode.
> I'm a bit pedantic so the conflation feels wrong to me regardless, but I
> think this will become increasingly confusing as alternative deployments
> without colocated HDFS DataNodes become more common (e.g. running against S3,
> running with a separate HDFS service).
> E.g. picking an example at random:
> {noformat}
> In Impala 1.4.0 and higher, the <codeph>LIMIT</codeph> clause is now
> optional (rather than required) for
> queries that use the <codeph>ORDER BY</codeph> clause. Impala
> automatically uses a temporary disk work area
> to perform the sort if the sort operation would otherwise exceed the
> Impala memory limit for a particular
> DataNode.
> {noformat}
> This is wrong because the memory limit is for an Impala daemon, which is the
> process that does the actual sorting. So here I think it should be "Impala
> daemon" instead of "DataNode".
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