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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
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ASF subversion and git services commented on IMPALA-9962:
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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 <impala-public-jenk...@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenk...@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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