Victoria Markman created DRILL-2543:
---------------------------------------
Summary: Correlated subquery where outer table contains NULL
values returns seemingly wrong result
Key: DRILL-2543
URL: https://issues.apache.org/jira/browse/DRILL-2543
Project: Apache Drill
Issue Type: Bug
Components: Query Planning & Optimization
Affects Versions: 0.8.0
Reporter: Victoria Markman
Assignee: Jinfeng Ni
Priority: Critical
{code}
0: jdbc:drill:schema=dfs> select * from t1;
+------------+------------+------------+
| a1 | b1 | c1 |
+------------+------------+------------+
| 1 | 2015-03-01 | aaaaa |
| 2 | 2015-03-02 | bbbbb |
| null | null | null |
+------------+------------+------------+
3 rows selected (0.064 seconds)
0: jdbc:drill:schema=dfs> select * from t2;
+------------+------------+------------+
| a2 | b2 | c2 |
+------------+------------+------------+
| 5 | 2017-03-01 | a |
+------------+------------+------------+
1 row selected (0.07 seconds)
0: jdbc:drill:schema=dfs> select t1.c1, count(*) from t1 where t1.b1 not in
(select b2 from t2 where t1.a1 = t2.a2) group by t1.c1 order by t1.c1;
+------------+------------+
| c1 | EXPR$1 |
+------------+------------+
| aaaaa | 1 |
| bbbbb | 1 |
+------------+------------+
2 rows selected (0.32 seconds)
{code}
Postgres returns row from the outer table where a1 is null.
This is part that I don't understand, because join condition in the subquery
should have eliminated row where a1 IS NULL. To me Drill result looks correct.
Unless there is something different in correlated comparison semantics that I'm
not aware of.
{code}
postgres=# select * from t1;
a1 | b1 | c1
----+------------+-------
1 | 2015-03-01 | aaaaa
2 | 2015-03-02 | bbbbb
| |
(3 rows)
{code}
Explain plan for the query:
{code}
00-01 Project(c1=[$0], EXPR$1=[$1])
00-02 StreamAgg(group=[{0}], EXPR$1=[COUNT()])
00-03 Sort(sort0=[$0], dir0=[ASC])
00-04 Project(c1=[$0])
00-05 SelectionVectorRemover
00-06 Filter(condition=[NOT(IS TRUE($3))])
00-07 HashJoin(condition=[=($1, $2)], joinType=[left])
00-09 Project($f1=[$0], $f3=[$2])
00-11 SelectionVectorRemover
00-13 Filter(condition=[IS NOT NULL($1)])
00-15 Project(c1=[$1], b1=[$0], a1=[$2])
00-17 Scan(groupscan=[ParquetGroupScan
[entries=[ReadEntryWithPath [path=maprfs:/test/t1]], selectionRoot=/test/t1,
numFiles=1, columns=[`c1`, `b1`, `a1`]]])
00-08 Project($f02=[$1], $f2=[$2])
00-10 StreamAgg(group=[{0, 1}], agg#0=[MIN($2)])
00-12 Sort(sort0=[$0], sort1=[$1], dir0=[ASC],
dir1=[ASC])
00-14 Project($f0=[$1], $f02=[$2], $f1=[true])
00-16 HashJoin(condition=[=($2, $0)],
joinType=[inner])
00-18 StreamAgg(group=[{0}])
00-20 Sort(sort0=[$0], dir0=[ASC])
00-22 Project($f0=[$1])
00-23 SelectionVectorRemover
00-24 Filter(condition=[IS NOT NULL($0)])
00-25 Scan(groupscan=[ParquetGroupScan
[entries=[ReadEntryWithPath [path=maprfs:/test/t1]], selectionRoot=/test/t1,
numFiles=1, columns=[`b1`, `a1`]]])
00-19 Project(a2=[$1], b2=[$0])
00-21 Scan(groupscan=[ParquetGroupScan
[entries=[ReadEntryWithPath [path=maprfs:/test/t2]], selectionRoot=/test/t2,
numFiles=1, columns=[`a2`, `b2`]]])
{code}
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