Global Dictionary is a MUST for bitmap count distinct; If not using GD, each segment will have an individual dictionary, the result will be wrong when merging across segments;
The GUI doesn't give warning on this, which is a bug; we need to enforce this. Create a JIRA to track this: https://issues.apache.org/jira/browse/KYLIN-3161 2018-01-11 20:01 GMT+08:00 张 佑铖 <[email protected]>: > Hi shaofeng, > > > Thank you for your reply. > > We use the current version 2.2.0. > > Actually I did not know the usage of Advanced Dictionaries before, > > after I add global dictionary for the column, it seems to be correct. > > So the global dictionary is for the situation like us? > > If I do not use global dictionary, every segment will associate with a > dictionary for a count distinct separately? > > And I also find out after I add the global dictionary the rate of > expansion does not increase > > > > ________________________________ > 发件人: ShaoFeng Shi <[email protected]> > 发送时间: 2018年1月11日 16:58 > 收件人: dev > 主题: Re: Calculate count distinct with 2 segments not correct > > Hi yousheng, > > Whatever the time range you queried, the result of count distinct > should/need be correct. And the segment merge shouldn't change the query > result. > > What's your Kylin version? Did you use the GlobalDictionary for the column > that doing distinct count? > > 2018-01-11 15:57 GMT+08:00 张 佑铖 <[email protected]>: > > > Hi Kylin team, > > > > > > > > In my cube, partition by date, auto merge by 7 days. > > > > And I use bitmap for count distinct. > > > > The case is I have 2 segments which is 20171229-20180105 and > > 20180105-20180112, I found that if the time of query in both 2 segments, > > the result of count distinct is not correct, > > > > after I merge the 2 segments and finally the result seems correct. > > > > So I have the question, if I want to calculate a count distinct with > > whenever start and whenever end, I should always merge all the segments? > > > > > > Thank you > > > > > > -- > Best regards, > > Shaofeng Shi 史少锋 > -- Best regards, Shaofeng Shi 史少锋
