tree 5dc71251cbd81169599c8d905e443a1baa434cbe
parent a8a35edbc407e02187279ac8d090a345d026c57a
author Gabor Kaszab <gaborkaszab@cloudera.com> 1598343613 +0200
committer Impala Public Jenkins <impala-public-jenkins@cloudera.com> 1598439589 +0000

IMPALA-10020: Implement ds_kll_cdf_as_string() function

This is the support for Cumulative Distribution Function (CDF) from
Apache DataSketches KLL algorithm collection. It receives a serialized
KLL sketch and one or more float values to represent ranges in the
sketched values.
E.g. [1, 5, 10] will mean the following ranges:
(-inf, 1), (-inf, 5), (-inf, 10), (-inf, +inf)
Returns a comma separated string where each value in the string is a
number in the range of [0,1] and shows that what percentage of the
data is in the particular ranges.

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

Example:
select ds_kll_cdf_as_string(ds_kll_sketch(float_col), 2, 4, 10)
from alltypes;
+----------------------------------------------------------+
| ds_kll_cdf_as_string(ds_kll_sketch(float_col), 2, 4, 10) |
+----------------------------------------------------------+
| 0.2,0.401644,1,1                                         |
+----------------------------------------------------------+

Change-Id: I77e6afc4556ad05a295b89f6d06c2e4a6bb2cf82
Reviewed-on: http://gerrit.cloudera.org:8080/16359
Reviewed-by: Gabor Kaszab <gaborkaszab@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>