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From hosur narahari <hnr1...@gmail.com>
Subject Re: select column returns null values
Date Mon, 24 Sep 2018 07:29:32 GMT
Hi ShaoFeng,

Thank you. I'll check that.

Best Regards,
Hari

On Mon, 24 Sep 2018, 11:59 ShaoFeng Shi, <shaofengshi@apache.org> wrote:

> Hi Hari,
>
> You're right that Cube has joined data (from fact and lookup tables), and
> then aggregate them by the dimensions. But Kylin doesn't keep the raw data
> after the cube be built, only keep the cuboid (group by certain
> dimensions), so couldn't answer the "select * " without "group by" query.
>
> The logic to pushdown is quite simple today. Please look at QueryService#executeRequest();
> When Cube throws an exception, it redirects to the pushdown engine.
>
> hosur narahari <hnr1992@gmail.com> 于2018年9月21日周五 上午11:11写道:
>
>> Hi ShaoFeng,
>>
>> Thanks for your response. I've few follow up questions.
>>
>> 1. In FAQ, it's mentioned that "The cube only has aggregated data, so
>> all your queries should be aggregated queries". But since cube is created
>> by joining based on various dimensions, shouldn't joins without aggregation
>> be valid cube querying scenarios(I hope it's already being done).
>>
>> 2. "select price from " statement should also be pushed down, the rule
>> can be optimized for it. Can you point me to documentation for specifying
>> pushdown rules. It would be of big help.
>>
>> Thanks & Regards,
>> Hari
>>
>> On Thu, Sep 20, 2018 at 5:27 PM ShaoFeng Shi <shaofengshi@apache.org>
>> wrote:
>>
>>> Hi Hosur,
>>>
>>> Firstly, please check Kylin's FAQ, search "Why I got an error when
>>> running a “select * “ query?":
>>> https://kylin.apache.org/docs/gettingstarted/faq.html
>>>
>>> Maybe the "select price from " statement should also be pushed down, the
>>> rule of pushdown can be optimized for it.
>>>
>>> hosur narahari <hnr1992@gmail.com> 于2018年9月20日周四 上午11:15写道:
>>>
>>>> Hi,
>>>>
>>>> I was trying out kylin with sample-cube example. And when I run
>>>> "select * from kylin_sales" query, it returns all the values correctly. But
>>>> when
>>>> I run "select price from kylin_sales", it returns null in all rows.
>>>> Price also was coming correctly in first scenario.
>>>>
>>>> One more thing is, first query is pushed down to hive and second one is
>>>> fetched from cube. And yes, I've enabled pushdown.
>>>>
>>>> Please let me know if I'm missing something.
>>>>
>>>> Best Regards,
>>>> Hari
>>>>
>>>
>>>
>>> --
>>> Best regards,
>>>
>>> Shaofeng Shi 史少锋
>>>
>>>
>
> --
> Best regards,
>
> Shaofeng Shi 史少锋
>
>

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