[jira] [Created] (IMPALA-9281) Inferred predicates not assigned to Kudu scan nodes when views are involved

["Fang-Yu Rao (Jira)" <ji...@apache.org>]

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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