Ted-Jiang opened a new pull request #1615:
URL: https://github.com/apache/kylin/pull/1615


   …be level
   
   ## Proposed changes
   
   
   We find many use cases should use cube-level lookup table snapshot instead 
of segment-level ones. For segment-level ones, it will cause many issues. For 
example for table BATCH_VIEWS.xxx, it changes everyday. Now there're around 
2000 snapshots.
   
   For building a new snapshot, it will check the duplication to avoid 
duplicated snapshots, which means it will check all of the 2000 snapshots. It 
really costs time.
   For query & building, to cache the snapshot, if each takes around 6MB, the 
total will need around 12GB memory.
   After this change, we can not only speedup cubing but also reduce the burden 
of memory cost.
   
   
   ## Types of changes
   
   What types of changes does your code introduce to Kylin?
   _Put an `x` in the boxes that apply_
   
   - [ ] Bugfix (non-breaking change which fixes an issue)
   - [x] New feature (non-breaking change which adds functionality)
   - [ ] Breaking change (fix or feature that would cause existing 
functionality to not work as expected)
   - [ ] Documentation Update (if none of the other choices apply)
   
   ## Checklist
   
   _Put an `x` in the boxes that apply. You can also fill these out after 
creating the PR. If you're unsure about any of them, don't hesitate to ask. 
We're here to help! This is simply a reminder of what we are going to look for 
before merging your code._
   
   - [ ] I have create an issue on [Kylin's 
jira](https://issues.apache.org/jira/browse/KYLIN), and have described the 
bug/feature there in detail
   - [ ] Commit messages in my PR start with the related jira ID, like 
"KYLIN-0000 Make Kylin project open-source"
   - [ ] Compiling and unit tests pass locally with my changes
   - [ ] I have added tests that prove my fix is effective or that my feature 
works
   - [ ] If this change need a document change, I will prepare another pr 
against the `document` branch
   - [ ] Any dependent changes have been merged
   
   ## Further comments
   
   If this is a relatively large or complex change, kick off the discussion at 
user@kylin or dev@kylin by explaining why you chose the solution you did and 
what alternatives you considered, etc...
   


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