Zoltan Haindrich created HIVE-18108:
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Summary: in case basic stats are missing; rowcount estimation
depends on the select columns size
Key: HIVE-18108
URL: https://issues.apache.org/jira/browse/HIVE-18108
Project: Hive
Issue Type: Sub-task
Reporter: Zoltan Haindrich
in case basicstats are not available (especially rowcount):
{code}
set hive.stats.autogather=false;
create table t (a integer, b string);
insert into t values (1,'asd1');
insert into t values (2,'asd2');
insert into t values (3,'asd3');
insert into t values (4,'asd4');
insert into t values (5,'asd5');
explain select a,count(1) from t group by a;
-- estimated to read 8 rows from table t
explain select b,count(1) from t group by b;
-- estimated: 1 rows
explain select a,b,count(1) from t group by a,b;
-- estimated: 1 rows
{code}
it may not depend on the actually selected column set.
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