lens-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Rajat Khandelwal <rajatgupt...@gmail.com>
Subject Re: Difference between Select and Cube Select
Date Thu, 25 Aug 2016 18:38:54 GMT
All drivers are asked to estimate. In the process of estimation, a driver
can fail, which lens server takes to mean that this driver cannot run this
query.

On Thu, Aug 25, 2016 at 10:32 PM Tao Yan <tyan@linkedin.com> wrote:

> If Lens find the table is not a cube/dimension and pass the query through
> to drivers, then, how does Lens decide which driver to use?  What if the
> driver picked is not the right one? For example, a query contains hive UDF
> is passed through to a MySQL database.
>
> Thanks,
>
> On Wed, Aug 24, 2016 at 11:47 PM, Rajat Khandelwal <rajatgupta59@gmail.com
> > wrote:
>
>> That doesn't happen. One driver is picked to run the query. The drivers
>> bid by providing their estimate of cost for running this query.
>>
>> On Thu, Aug 25, 2016 at 1:47 AM Tao Yan <tyan@linkedin.com> wrote:
>>
>>> If the query is executed in multiple drivers, and more than one drivers
>>> return the result, then, how does Lens decide which result to return to
>>> user? And if one driver return result before others, will Lens wait for
>>> other drivers?
>>>
>>> Thanks,
>>>
>>> On Wed, Aug 24, 2016 at 12:00 AM, Rajat Khandelwal <
>>> rajatgupta59@gmail.com> wrote:
>>>
>>>> Yes, it can be any standard sql. The logic in lens is to check the from
>>>> clause, and if the entity in the from-clause is either a cube or a
>>>> dimension, then treat it as cube query, and do the translation before
>>>> running this query. If it's not a cube or a dimension, it's treated as a
>>>> native query and all the drivers are forwarded this query as it is without
>>>> any translation.
>>>>
>>>>
>>>> On Wed, Aug 24, 2016 at 5:43 AM Tao Yan <tyan@linkedin.com> wrote:
>>>>
>>>>> When using "select" (not "cube select"), can it be any standard SQL
>>>>> (not bounded to Lens QL)?
>>>>>
>>>>> Thanks!
>>>>>
>>>>> On Tue, Aug 23, 2016 at 4:57 PM, amareshwarisr . <
>>>>> amareshwari@gmail.com> wrote:
>>>>>
>>>>>> cube select expects the from clause to be on cube/dimension. select
>>>>>> is the one in SQL.
>>>>>>
>>>>>> Going forward from 2.6 onwards, cube keyword is optional for
>>>>>> cube/dimension queries.
>>>>>>
>>>>>> Thanks
>>>>>>
>>>>>> On Wed, Aug 24, 2016 at 3:53 AM, Tao Yan <tyan@linkedin.com>
wrote:
>>>>>>
>>>>>>> Hi Lens Developer,
>>>>>>>
>>>>>>> I found the following example in
>>>>>>> https://github.com/apache/lens/blob/master/lens-examples/src/main/resources/dimension-queries.sql
>>>>>>>
>>>>>>> select * from (cube select sample_dim.name name1, sample_dim2_chain.
>>>>>>> name name2 from sample_dim where sample_dim.name !='first') a
>>>>>>>
>>>>>>> I tested "cube select * " and it didn't work, and the above example
>>>>>>> shows "select *". What is the difference between "select" and
"cube select"?
>>>>>>>
>>>>>>> Thanks,
>>>>>>> --
>>>>>>>
>>>>>>> *Tao Yan*
>>>>>>> Software Engineer
>>>>>>> Data Analytics Infrastructure Tools and Services
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>> 206.250.5345
>>>>>>> tyan@linkedin.com
>>>>>>> https://www.linkedin.com/in/taousc
>>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>> --
>>>>>
>>>>> *Tao Yan*
>>>>> Software Engineer
>>>>> Data Analytics Infrastructure Tools and Services
>>>>>
>>>>>
>>>>>
>>>>> 206.250.5345
>>>>> tyan@linkedin.com
>>>>> https://www.linkedin.com/in/taousc
>>>>>
>>>>
>>>
>>>
>>> --
>>>
>>> *Tao Yan*
>>> Software Engineer
>>> Data Analytics Infrastructure Tools and Services
>>>
>>>
>>>
>>> 206.250.5345
>>> tyan@linkedin.com
>>> https://www.linkedin.com/in/taousc
>>>
>>
>
>
> --
>
> *Tao Yan*
> Software Engineer
> Data Analytics Infrastructure Tools and Services
>
>
>
> 206.250.5345
> tyan@linkedin.com
> https://www.linkedin.com/in/taousc
>

Mime
View raw message