[IMPALA-10017] Implement ds_kll_union() function

• Type: New Feature
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: Impala 4.0.0
• Component/s: Backend, Frontend
• Epic Link: unlabelled-IMPALA-9594
• Epic Color: ghx-label-5
• Assignee: Gabor Kaszab
• Reporter: Gabor Kaszab
• Created: 29/Jul/20 07:56
• Updated: 11/Aug/20 04:06
• Resolved: 10/Aug/20 12:16

Description

Similarly to https://issues.apache.org/jira/browse/IMPALA-9633 DataSketches KLL also has union functionality.

ds_kll_union() expects a dataset of STRINGs (e.g. column of a table) that represents serialized KLL sketches and returns a single STRING that is the received sketches unioned and serialized.