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Posted to dev@kylin.apache.org by Ding Dinghua <di...@gmail.com> on 2016/08/16 13:00:40 UTC
about count(a particular column) in kylin
Hi:
Does kylin support count(a particular column) now?
that is, count will skip rows which the particular column value is null.
In our test, I found it is not supported currently(kylin-1.5.2),
and I found that agg->aggCalls->arglist is null in
OLAPAggregateRule::convert when I submmit sql like:
select dt, count(xxx) from test_table group by dt;
The information about the particular column is lost in kylin, so I
want to know why?
Since I found count(xxx) is support in calcite:
https://calcite.apache.org/docs/reference.html
--
Ding Dinghua
Re: about count(a particular column) in kylin
Posted by Yerui Sun <su...@gmail.com>.
Kylin can’t support count(not null) directly, but there’s workaround.
Let’s say you have column ‘col1’, and want calculate count(col1 not null), you should create a new column ‘col2’, which col2 = if(col1 is not null, 1, 0), and then you can define a measure sum(col2) in kylin.
> 在 2016年8月17日，15:17，Ding Dinghua <di...@gmail.com> 写道：
>
> ping...
>
> 2016-08-16 21:00 GMT+08:00 Ding Dinghua <di...@gmail.com>:
>> Hi:
>> Does kylin support count(a particular column) now?
>> that is, count will skip rows which the particular column value is null.
>> In our test, I found it is not supported currently(kylin-1.5.2),
>> and I found that agg->aggCalls->arglist is null in
>> OLAPAggregateRule::convert when I submmit sql like:
>> select dt, count(xxx) from test_table group by dt;
>> The information about the particular column is lost in kylin, so I
>> want to know why?
>> Since I found count(xxx) is support in calcite:
>> https://calcite.apache.org/docs/reference.html
>>
>> --
>> Ding Dinghua
>
>
>
> --
> Ding Dinghua
Re: about count(a particular column) in kylin
Posted by Ding Dinghua <di...@gmail.com>.
ping...
2016-08-16 21:00 GMT+08:00 Ding Dinghua <di...@gmail.com>:
> Hi:
> Does kylin support count(a particular column) now?
> that is, count will skip rows which the particular column value is null.
> In our test, I found it is not supported currently(kylin-1.5.2),
> and I found that agg->aggCalls->arglist is null in
> OLAPAggregateRule::convert when I submmit sql like:
> select dt, count(xxx) from test_table group by dt;
> The information about the particular column is lost in kylin, so I
> want to know why?
> Since I found count(xxx) is support in calcite:
> https://calcite.apache.org/docs/reference.html
>
> --
> Ding Dinghua
--
Ding Dinghua