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https://issues.apache.org/jira/browse/HIVE-2925?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14052991#comment-14052991
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Lefty Leverenz commented on HIVE-2925:
--------------------------------------
*hive.fetch.task.conversion* is documented in the wiki here, next to the other
fetch task parameters:
* [Configuration Properties -- hive.fetch.task.conversion |
https://cwiki.apache.org/confluence/display/Hive/Configuration+Properties#ConfigurationProperties-hive.fetch.task.conversion]
Question 1: What does RS mean in the parameter description: "should not have
any aggregations or distincts (which incurs RS)"? Is it ReduceSinkOperator as
in HIVE-5056?
Question 2: What do "LIMIT only" and "LIMIT only (TABLESAMPLE, virtual
columns)" mean? I don't see why the latter is less restrictive than the
former, even after checking the wiki:
[https://cwiki.apache.org/confluence/display/Hive/LanguageManual+Select#LanguageManualSelect-LIMITClause].
Question 3: Does FILTER just mean the WHERE and HAVING clauses? If it isn't
syntax, shouldn't it be lowercase in the explanations of minimal and more (and
STAR be *)?
# minimal: SELECT *, filter on partition columns, LIMIT only
# more: SELECT, filter, LIMIT only (TABLESAMPLE, virtual columns)
> Support non-MR fetching for simple queries with select/limit/filter
> operations only
> -----------------------------------------------------------------------------------
>
> Key: HIVE-2925
> URL: https://issues.apache.org/jira/browse/HIVE-2925
> Project: Hive
> Issue Type: Improvement
> Affects Versions: 0.10.0
> Reporter: Navis
> Assignee: Navis
> Priority: Trivial
> Fix For: 0.10.0
>
> Attachments: ASF.LICENSE.NOT.GRANTED--HIVE-2925.D2607.1.patch,
> ASF.LICENSE.NOT.GRANTED--HIVE-2925.D2607.2.patch,
> ASF.LICENSE.NOT.GRANTED--HIVE-2925.D2607.3.patch,
> ASF.LICENSE.NOT.GRANTED--HIVE-2925.D2607.4.patch, HIVE-2925.1.patch.txt,
> HIVE-2925.2.patch.txt, HIVE-2925.3.patch.txt
>
>
> It's trivial but frequently asked by end-users. Currently, select queries
> with simple conditions or limit should run MR job which takes some time
> especially for big tables, making the people irritated.
> For that kind of simple queries, using fetch task would make them happy.
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