GitHub user wangyum opened a pull request:
https://github.com/apache/spark/pull/22250
[SPARK-25259][SQL] left/right join support push down during-join predicates
## What changes were proposed in this pull request?
Prepare data:
```sql
create temporary view EMPLOYEE as select * from values
("000010", "HAAS", "A00"),
("000010", "THOMPSON", "B01"),
("000030", "KWAN", "C01"),
("000110", "LUCCHESSI", "A00"),
("000120", "O'CONNELL", "A))"),
("000130", "QUINTANA", "C01")
as EMPLOYEE(EMPNO, LASTNAME, WORKDEPT);
create temporary view DEPARTMENT as select * from values
("A00", "SPIFFY COMPUTER SERVICE DIV.", "000010"),
("B01", "PLANNING", "000020"),
("C01", "INFORMATION CENTER", "000030"),
("D01", "DEVELOPMENT CENTER", null)
as EMPLOYEE(DEPTNO, DEPTNAME, MGRNO);
create temporary view PROJECT as select * from values
("AD3100", "ADMIN SERVICES", "D01"),
("IF1000", "QUERY SERVICES", "C01"),
("IF2000", "USER EDUCATION", "E01"),
("MA2100", "WELD LINE AUDOMATION", "D01"),
("PL2100", "WELD LINE PLANNING", "01")
as EMPLOYEE(PROJNO, PROJNAME, DEPTNO);
```
For the below SQL, we can push `DEPTNO='E01'` to right side to reduce data
reading:
```sql
SELECT PROJNO, PROJNAME, P.DEPTNO, DEPTNAME
FROM PROJECT P LEFT OUTER JOIN DEPARTMENT D
ON P.DEPTNO = D.DEPTNO AND P.DEPTNO='E01';
```
Optimized SQL is equivalent to:
```sql
SELECT PROJNO, PROJNAME, P.DEPTNO, DEPTNAME
FROM PROJECT P LEFT OUTER JOIN (SELECT * FROM DEPARTMENT WHERE
DEPTNO='E01') D
ON P.DEPTNO = D.DEPTNO AND P.DEPTNO='E01';
```
This pr enhancement `PushPredicateThroughJoin` to support this feature.
## How was this patch tested?
unit tests
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/wangyum/spark SPARK-25259
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/spark/pull/22250.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #22250
----
commit f9b32d5d044a899529959ad5042f8cf95c789ea8
Author: Yuming Wang <yumwang@...>
Date: 2018-08-28T06:18:05Z
left/right join support push down during-join predicates
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