[jira] [Commented] (IMPALA-9962) Implement ds_kll_quantiles() function

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    [ https://issues.apache.org/jira/browse/IMPALA-9962?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17184750#comment-17184750 ] 

ASF subversion and git services commented on IMPALA-9962:
---------------------------------------------------------

Commit 41065845e927acef5a0ff95ef8fb32b2f86272d8 in impala's branch refs/heads/master from Gabor Kaszab
[ https://gitbox.apache.org/repos/asf?p=impala.git;h=4106584 ]

IMPALA-9962: Implement ds_kll_quantiles_as_string() function

This function is very similar to ds_kll_quantile() but this one can
receive any number of rank parameters and returns a comma separated
string that holds the results for all of the given ranks.
For more details about ds_kll_quantile() see IMPALA-9959.

Note, ds_kll_quantiles() should return an Array of floats as the result
but with that we have to wait for the complex type support. Until, we
provide ds_kll_quantiles_as_string() that can be deprecated once we
have array support. Tracking Jira for returning complex types from
functions is IMPALA-9520.

Change-Id: I76f6039977f4e14ded89a3ee4bc4e6ff855f5e7f
Reviewed-on: http://gerrit.cloudera.org:8080/16324
Reviewed-by: Impala Public Jenkins <im...@cloudera.com>
Tested-by: Impala Public Jenkins <im...@cloudera.com>


> Implement ds_kll_quantiles() function
> -------------------------------------
>
>                 Key: IMPALA-9962
>                 URL: https://issues.apache.org/jira/browse/IMPALA-9962
>             Project: IMPALA
>          Issue Type: Improvement
>          Components: Backend
>            Reporter: Gabor Kaszab
>            Assignee: Gabor Kaszab
>            Priority: Major
>
> Requirements for ds_kll_quantiles()
>  - Receives a serialized KLL sketch in BINARY type (in Impala it can be STRING as long as we don't have BINARY) as first parameter.
>  - Receives one or more double values to represent the quantile points.
>  - In Hive the return type is an array of doubles. However, Impala can't return complex types from functions at this point so we have to find some alternative approaches to implement this function.
>  ** One would be to return as many columns as many quantile points were given.
>  ** Another approach is to create a comma separated string from the results of this function and return that string instead of an array.
> Hive example:
> {code:java}
> select ds_kll_quantiles(ds_kll_sketch(cast(int_col as float)), 0, 0.1, 0.5, 1) from table_name
> +--------------------+
> |        _c0         |
> +--------------------+
> | [1.0,1.0,1.0,1.0]  |
> +--------------------+
> {code}



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