commit dcdbaf12224e7029dde3110d56edea022dd3a2a0
author xqhe <hexianqing312@126.com> Mon Sep 21 18:19:18 2020 +0800
committer Impala Public Jenkins <impala-public-jenkins@cloudera.com> Tue Sep 22 22:19:41 2020 +0000
tree d69e898ae970a8009580a586d24300636f4bd0e6
parent 462d91884fed4a139587a9e5ffa353b82e486c95

IMPALA-5022 part 1: Implement core functions of outer join simplification

Outer joins in SQL can return rows with certain columns filled with
NULLs when a match can not be found. However, such rows can be
rejected by null-rejecting predicates. The conditions in a null-rejecting
predicate that are always evaluated to FALSE for NULLs are referred to
as null-filtering conditions.

In general, an outer join can be converted to an inner join if there
exist null-filtering conditions on the inner tables. In a left outer
join, the right table is the inner table, while in a right outer join
it is the left table. In a full outer join, both tables are inner tables.

The option ENABLE_OUTER_JOIN_TO_INNER_TRANSFORMATION enables or disables
the entire rewrite. This is False by default until we have done more
thorough functional testing.

For example,
1. A LEFT JOIN B ON A.id = B.id WHERE B.v > 10
= A INNER JOIN B ON A.id = B.id WHERE B.v > 10

2. A RIGHT JOIN B ON A.id = B.id WHERE A.v > 10
= A INNER JOIN B ON A.id = B.id WHERE A.v > 10

3. A FULL JOIN B ON A.id = B.id WHERE A.v > 10
= A LEFT JOIN B ON A.id = B.id WHERE A.v > 10

4. A FULL JOIN B ON A.id = B.id WHERE B.v > 10
= A RIGHT JOIN B ON A.id = B.id WHERE B.v > 10

5. A FULL JOIN B ON A.id = B.id WHERE A.v > 10 AND B.v > 10
= A INNER JOIN B ON A.id = B.id WHERE A.v > 10 AND B.v > 10

6. A LEFT JOIN B ON A.id = B.id INNER JOIN C ON B.id = C.id
= A INNER JOIN B ON A.id = B.id INNER JOIN C ON B.id = C.id

7. A RIGHT JOIN B ON A.id = B.id INNER JOIN C ON A.id = C.id
= A INNER JOIN B ON A.id = B.id INNER JOIN C ON A.id = C.id

8. A FULL JOIN B ON A.id = B.id INNER JOIN C ON A.id = C.id
= A LEFT JOIN B ON A.id = B.id INNER JOIN C ON A.id = C.id

9. A FULL JOIN B ON A.id = B.id INNER JOIN C ON B.id = C.id
= A RIGHT JOIN B ON A.id = B.id INNER JOIN C ON B.id = C.id

10. A FULL JOIN B ON A.id = B.id INNER JOIN C ON A.id + B.id = C.id
= A INNER JOIN B ON A.id = B.id INNER JOIN C ON A.id + B.id = C.id

In this commit, we have supported most of the cases that can convert
an outer join to an inner join, except for converting the embedding
inline view outer join by the join condition like
"SELECT * FROM T1 JOIN (SELECT T3.A A FROM T2 LEFT JOIN T3
ON T3.B=T2.B) T4 ON T4.A=T1.A". We will support it in part 2.

Tests:
* Add new plan tests outer-to-inner-joins.test
* Add new query tests to verify the correctness on transformation
* Ran the full set of verifications in Impala Public Jenkins

Change-Id: Iaa7804033fac68e93f33c387dc68ef67f803e93e
Reviewed-on: http://gerrit.cloudera.org:8080/16266
Reviewed-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>
Tested-by: Impala Public Jenkins <impala-public-jenkins@cloudera.com>