[jira] [Updated] (KYLIN-3490) For single column queries, only dictionaries are enough

["Shaofeng SHI (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/KYLIN-3490?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Shaofeng SHI updated KYLIN-3490:
--------------------------------
    Summary: For single column queries, only dictionaries are enough  (was: For some single column related queries, don't need to query cuboids, only dictionaries are enough)

> For single column queries, only dictionaries are enough
> -------------------------------------------------------
>
>                 Key: KYLIN-3490
>                 URL: https://issues.apache.org/jira/browse/KYLIN-3490
>             Project: Kylin
>          Issue Type: Improvement
>            Reporter: Zhong Yanghong
>            Assignee: Zhong Yanghong
>            Priority: Major
>             Fix For: v2.5.0
>
>         Attachments: APACHE-KYLIN-3490.patch
>
>
> A common use case for BI tools is as follows:
> # Firstly, extract all of the values of a dimension column
> # Then, select part of the values as filter condition.
> Previously query for the first step requires to hit all of the segments' cuboid data, which may not be efficient, especially when the segments occupy many regions. 
> To use dictionary rather than cuboid data to answer this kind of queries, will reduce the cost of many rpcs to hbase.
> Sample queries are as follows:
> {code}
> select A
> from T
> group by A
> {code}
> {code}
> select distinct A
> from T
> {code}
> {code}
> select max(A)
> from T
> {code}



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