Fang-Yu Rao created IMPALA-9281:
-----------------------------------
Summary: Inferred predicates not assigned to Kudu scan nodes when
views are involved
Key: IMPALA-9281
URL: https://issues.apache.org/jira/browse/IMPALA-9281
Project: IMPALA
Issue Type: Bug
Components: Frontend
Affects Versions: Impala 3.4.0
Reporter: Fang-Yu Rao
When a query involves the join of views each created based on multiple Kudu
tables, the inferred predicate(s) is(are) not assigned to the Kudu scan
node(s). This issue is/seems related to
https://issues.apache.org/jira/browse/IMPALA-4578#.
In the following a minimum example to reproduce the phenomenon is given.To
create the tables in the provided example below, please replace the address(es)
of the Kudu master(s) accordingly.
{code:java}
CREATE TABLE default.t1 (
c1 INT NOT NULL ENCODING AUTO_ENCODING COMPRESSION DEFAULT_COMPRESSION,
c2 STRING NULL ENCODING AUTO_ENCODING COMPRESSION DEFAULT_COMPRESSION,
PRIMARY KEY (c1)
)
PARTITION BY HASH (c1) PARTITIONS 2
STORED AS KUDU
TBLPROPERTIES ('kudu.master_addresses'='10.16.0.115');
insert into t1 values (1, 'one');
CREATE TABLE default.t2 (
c1 INT NOT NULL ENCODING AUTO_ENCODING COMPRESSION DEFAULT_COMPRESSION,
c2 STRING NULL ENCODING AUTO_ENCODING COMPRESSION DEFAULT_COMPRESSION,
PRIMARY KEY (c1)
)
PARTITION BY HASH (c1) PARTITIONS 2
STORED AS KUDU
TBLPROPERTIES ('kudu.master_addresses'='10.16.0.115');
insert into t2 values (2, 'two');
CREATE TABLE default.ta1 (
c1 INT NOT NULL ENCODING AUTO_ENCODING COMPRESSION DEFAULT_COMPRESSION,
c2 STRING NULL ENCODING AUTO_ENCODING COMPRESSION DEFAULT_COMPRESSION,
PRIMARY KEY (c1)
)
PARTITION BY HASH (c1) PARTITIONS 2
STORED AS KUDU
TBLPROPERTIES ('kudu.master_addresses'='10.16.0.115');
insert into ta1 values (1,'one');
CREATE TABLE default.ta2 (
c1 INT NOT NULL ENCODING AUTO_ENCODING COMPRESSION DEFAULT_COMPRESSION,
c2 STRING NULL ENCODING AUTO_ENCODING COMPRESSION DEFAULT_COMPRESSION,
PRIMARY KEY (c1)
)
PARTITION BY HASH (c1) PARTITIONS 2
STORED AS KUDU
TBLPROPERTIES ('kudu.master_addresses'='10.16.0.115');
insert into ta2 values (2,'two');
CREATE VIEW myview_1_on_2_tables AS
SELECT 'ONE' table_source, c1, c2 FROM `default`.t1
UNION ALL
SELECT 'TWO' table_source, c1, c2 FROM `default`.t2;
CREATE VIEW myview_2_on_2_tables AS
SELECT 'ONE' table_source, c1, c2 FROM `default`.ta1
UNION ALL
SELECT 'TWO' table_source, c1, c2 FROM `default`.ta2;
{code}
For easy reference, the contents of tables {{t1}}, {{t2}}, {{ta1}}, {{ta2}},
and views {{myview_1_on_2_tables}}, {{myview_2_on_2_tables}} are also given as
follows.
Contents of table {{t1}} afterwards:
{code:java}
+----+-----+
| c1 | c2 |
+----+-----+
| 1 | one |
+----+-----+
{code}
Contents of table {{t2}} afterwards:
{code:java}
+----+-----+
| c1 | c2 |
+----+-----+
| 2 | two |
+----+-----+
{code}
Contents of table {{ta1}} afterwards:
{code:java}
+----+-----+
| c1 | c2 |
+----+-----+
| 1 | one |
+----+-----+
{code}
Contents of table {{ta2}} afterwards:
{code:java}
+----+-----+
| c1 | c2 |
+----+-----+
| 2 | two |
+----+-----+
{code}
Contents in {{default.myview_1_on_2_tables}}:
{code:java}
+--------------+----+-----+
| table_source | c1 | c2 |
+--------------+----+-----+
| ONE | 1 | one |
| TWO | 2 | two |
+--------------+----+-----+
{code}
Contents in {{default.myview_2_on_2_tables}}:
{code:java}
+--------------+----+-----+
| table_source | c1 | c2 |
+--------------+----+-----+
| ONE | 1 | one |
| TWO | 2 | two |
+--------------+----+-----+
{code}
After creating the related tables and views described above, we consider the
following 2 queries.
Query 1:
{code:java}
select count(*)
from default.myview_1_on_2_tables a, myview_2_on_2_tables b
where a.table_source = 'ONE'
and a.table_source = b.table_source
and a.c2 = 'one';
{code}
Query 2:
{code:java}
select count(*)
from default.myview_1_on_2_tables a, myview_2_on_2_tables b
where a.table_source = 'ONE'
and b.table_source = 'ONE'
and a.table_source = b.table_source
and a.c2 = 'one';
{code}
Both queries join those 2 views on the column {{table_source}} and filter out
those rows not satisfying {{table_source = 'ONE'}}. Both queries produce the
same result set as the following.
{code:java}
+----------+
| count(*) |
+----------+
| 1 |
+----------+
{code}
However, according to the query profile, Query 1 results in 3 Kudu scans on
tables {{t1}}, {{ta1}}, and {{ta2}}, respectively. On the other hand, Query 2
that incorporates the additional/redundant predicate "{{b.table_source =
'ONE}}'" only involves 2 Kudu scans on tables {{t1}} and {{ta1}}, respectively
due to this seemingly redundant predicate on {{b.table_source}}.
Hence, it can be seen that the plan generated from Query 1 is sub-optimal since
a table that cannot contain any row in the result set is still scanned, i.e.,
table {{ta2}}.
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