Paul Rogers created IMPALA-8030:
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Summary: Remove duplicate in-clause values for selectivity calcs
Key: IMPALA-8030
URL: https://issues.apache.org/jira/browse/IMPALA-8030
Project: IMPALA
Issue Type: Improvement
Components: Frontend
Affects Versions: Impala 3.1.0
Reporter: Paul Rogers
Assignee: Paul Rogers
If an IN clause has duplicate values, they should be removed so that
selectivity estimates are based only on unique values.
{noformat}
select *
from tpch.customer c
where c.c_custkey in (10, 20, 30, 30, 10, 20)
---- PLAN
PLAN-ROOT SINK
|
00:SCAN HDFS [tpch.customer c]
partitions=1/1 files=1 size=23.08MB row-size=218B cardinality=6
predicates: c.c_custkey IN (10, 20, 30, 30, 10, 20)
{noformat}
Expected:
{noformat}
00:SCAN HDFS [tpch.customer c]
partitions=1/1 files=1 size=23.08MB row-size=218B cardinality=3
{noformat}
Notice that in the current version, we treat each value, duplicate or not, as a
match. In the expected result, we notice that duplicate values match only once
and we return matches for the unique values.
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