[HIVE-19097] related equals and in operators may cause inaccurate stats estimations

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 4.0.0-alpha-1
• Assignee: Zoltan Haindrich
• Reporter: Zoltan Haindrich
• Created: 03/Apr/18 11:45
• Updated: 27/Feb/24 22:24
• Resolved: 06/Aug/18 05:48

Description

tpcds#74 is optimized in a way that for date_dim the condition contains IN and = for the same column

|             Map Operator Tree:                     |
|                 TableScan                          |
|                   alias: date_dim                  |
|                   filterExpr: (((d_year) IN (2001, 2002) and (d_year = 2002) and d_date_sk is not null) or ((d_year) IN (2001, 2002) and (d_year = 2001) and d_date_sk is not null)) (type: boolean) |
|                   Statistics: Num rows: 73049 Data size: 876588 Basic stats: COMPLETE Column stats: COMPLETE |
|                   Filter Operator                  |
|                     predicate: ((d_year) IN (2001, 2002) and (d_year = 2002) and d_date_sk is not null) (type: boolean) |
|                     Statistics: Num rows: 4 Data size: 48 Basic stats: COMPLETE Column stats: COMPLETE |

the "real" row count will be 365

for separate IN and = the estimation is very good; but if both are present it becomes (very) underestimated.

set hive.query.results.cache.enabled=false;

drop table if exists t1;
drop table if exists t8;

create table t1 (a integer,b integer);
create table t8 like t1;

insert into t1 values (1,1),(2,2),(3,3),(4,4),(5,5);

insert into t8
select * from t1 union all select * from t1 union all select * from t1 union all select * from t1 union all
select * from t1 union all select * from t1 union all select * from t1 union all select * from t1
;

analyze table t1 compute statistics for columns;
analyze table t8 compute statistics for columns;

explain analyze select sum(a) from t8 where b in (2,3) group by b;
explain analyze select sum(a) from t8 where b=2 group by b;

explain analyze select sum(a) from t1 where b in (2,3) and b=2 group by b;
explain analyze select sum(a) from t8 where b in (2,3) and b=2 group by b;

Issue Links

• duplicates: HIVE-21074 Hive bucketed table query pruning does not work for IS NOT NULL condition
• is related to: CALCITE-2247 Simplify AND and OR conditions using predicates
• links to: reviewboard

Sub-Tasks

• Prevent multiple selectivity estimations for the same variable in conjuctions: Closed