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https://issues.apache.org/jira/browse/IMPALA-9959?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17184751#comment-17184751
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ASF subversion and git services commented on IMPALA-9959:
---------------------------------------------------------
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_sketch() and ds_kll_quantile() functions
> ---------------------------------------------------------
>
> Key: IMPALA-9959
> URL: https://issues.apache.org/jira/browse/IMPALA-9959
> Project: IMPALA
> Issue Type: Improvement
> Components: Backend, Frontend
> Reporter: Gabor Kaszab
> Assignee: Gabor Kaszab
> Priority: Major
> Fix For: Impala 4.0
>
>
> 1:
> STRING ds_kll_sketch(float)
> Accepts float as parameter and returns a DataSketches KLL sketch in string
> type (or binary once that work is submitted).
> 2:
> FLOAT (or DOUBLE?) ds_kll_quantile(KLL sketch, double)
> Accepts two parameters: a KLL sketch created by ds_hll_sketch() and a double
> in [0, 1] to represent the quantile.
> At this point I'm not sure about the return value, it's either a float or
> double, it's a subject of further investigation.
> Example:
> {code:java}
> select ds_kll_quantile(ds_kll_sketch(cast(int_col as float)), 1) from
> table_name;
> +------+
> | _c0 |
> +------+
> | 1.0 |
> +------+
> {code}
> Some further examples found here:
> [https://datasketches.apache.org/docs/Quantiles/QuantilesCppExample.html]
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