[jira] [Commented] (METRON-932) Change HLLP Stellar functions to accept empty lists

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/METRON-932?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15997738#comment-15997738 ] 

ASF GitHub Bot commented on METRON-932:
---------------------------------------

GitHub user mmiklavc opened a pull request:

    https://github.com/apache/incubator-metron/pull/566

    METRON-932: Change HLLP Stellar functions to accept empty lists

    https://issues.apache.org/jira/browse/METRON-932
    
    I changed the unit tests and README to reflect the new functionality. You can test this feature change by spinning up the Stellar REPL and executing the following example. If you wish test locally using the Stellar REPL, this can be done by doing the following:
    ```
    $ cd ${METRON_HOME}/metron-analytics/metron-statistics/target
    $ java -cp metron-statistics-0.4.0.jar org.apache.metron.common.stellar.shell.StellarShell
    ```
    
    Test example:
    ```
    1 [Stellar]>>> foo := []
    2 [Stellar]>>> set1 := HLLP_MERGE(foo)
    3 [Stellar]>>> set1
    4 [Stellar]>>> HLLP_CARDINALITY(set1)
    0
    5 [Stellar]>>> foo := [HLLP_INIT(5,6)]
    6 [Stellar]>>> set1 := HLLP_MERGE(foo)
    7 [Stellar]>>> set1
    org.apache.metron.statistics.approximation.HyperLogLogPlus@1
    ```
    
    Note that step 2 should NOT throw an exception any longer. Step 3 will produce no output because `set1` is null. Step 4 shows that cardinality on a null argument now returns 0. Note how the output differs for `set1` in step 7 after passing in a list that is not empty - it will list the HLLP set reference.
    
    ### For all changes:
    - [x] Is there a JIRA ticket associated with this PR? If not one needs to be created at [Metron Jira](https://issues.apache.org/jira/browse/METRON/?selectedTab=com.atlassian.jira.jira-projects-plugin:summary-panel). 
    - [x] Does your PR title start with METRON-XXXX where XXXX is the JIRA number you are trying to resolve? Pay particular attention to the hyphen "-" character.
    - [x] Has your PR been rebased against the latest commit within the target branch (typically master)?
    
    
    ### For code changes:
    - [x] Have you included steps to reproduce the behavior or problem that is being changed or addressed?
    - [x] Have you included steps or a guide to how the change may be verified and tested manually?
    - [x] Have you ensured that the full suite of tests and checks have been executed in the root incubating-metron folder via:
      ```
      mvn -q clean integration-test install && build_utils/verify_licenses.sh 
      ```
    
    - [x] Have you written or updated unit tests and or integration tests to verify your changes?
    - [ ] If adding new dependencies to the code, are these dependencies licensed in a way that is compatible for inclusion under [ASF 2.0](http://www.apache.org/legal/resolved.html#category-a)? 
    - [ ] Have you verified the basic functionality of the build by building and running locally with Vagrant full-dev environment or the equivalent?
    
    ### For documentation related changes:
    - [ ] Have you ensured that format looks appropriate for the output in which it is rendered by building and verifying the site-book? If not then run the following commands and the verify changes via `site-book/target/site/index.html`:
    
      ```
      cd site-book
      mvn site
      ```
    


You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/mmiklavc/incubator-metron METRON-932

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/incubator-metron/pull/566.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #566
    
----
commit e0cf2e22106b02c507da43c75bdead4c0acf0ba8
Author: Michael Miklavcic <mi...@gmail.com>
Date:   2017-05-05T01:22:29Z

    METRON-932: Change HLLP Stellar functions to accept empty lists

----


> Change HLLP Stellar functions to accept empty lists
> ---------------------------------------------------
>
>                 Key: METRON-932
>                 URL: https://issues.apache.org/jira/browse/METRON-932
>             Project: Metron
>          Issue Type: Improvement
>            Reporter: Michael Miklavcic
>            Assignee: Michael Miklavcic
>
> The current implementation, which disallows merging empty sets, makes interactions via the Profiler more complex than they need to be. This Jira would change the argument handling to allow empty lists. The resulting functionality should treat cardinality of a null set as zero.



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