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From "Thomas Nielsen (JIRA)" <j...@apache.org>
Subject [jira] Commented: (DERBY-3301) Incorrect result from query with nested EXIST
Date Mon, 21 Jan 2008 08:36:42 GMT

    [ https://issues.apache.org/jira/browse/DERBY-3301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12560953#action_12560953
] 

Thomas Nielsen commented on DERBY-3301:
---------------------------------------

Dyre> Are you saying that the query behaves correctly?
No, it does not on the current trunk. And your understanding of how this should be evaluated
is correct I believe. Also see Craigs comment above.

Craig> As an optimization, you could invert the scan and look at all of the rows of the
join table. 
Looking at the queryplan I think this is what Derby does, and during this optimization something
goes wrong.

As Bryan suggests, flattening of the exists query could be what goes wrong. I didn't see any
obvious errors in the methods he suggested though.

The problem appears since the NestedLoopJoinResultSet above the HashScanResultSet that returns
3 out of 7 rows, incorrectly has its right side 
"optimized" to expect a single row since it's flagged as an EXISTS query. This causes NestedLoopJoinResultSet
to retrieve 1 row, then close and reopen the 
HashScanResultSet subquery which then returns from the next hash bucket like it's supposed
to. This way we continue through the 3 hash buckets returning 3 out of 7 rows.

As I stated in my last comment (the long one), if the NestedLoopJoinResultSet has it's right
child (correctly) flagged as *not* being an EXISTS query 
and expected to return a single row, the query returns the expected 7 rows. So we need to
figure out the root cause of why the NesteLoopJoinResultSet 
thinks its right child will return only one row.

> Incorrect result from query with nested EXIST
> ---------------------------------------------
>
>                 Key: DERBY-3301
>                 URL: https://issues.apache.org/jira/browse/DERBY-3301
>             Project: Derby
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 10.1.3.1, 10.2.1.6, 10.3.2.1
>            Reporter: Craig Russell
>         Attachments: d3301-queryplan.log, derby-3301.sql
>
>
> Derby returns unexpected results from a query with embedded EXIST clauses. The query
SQL is generated by the JPOX jdo implementation and is supposed to return all of the PERSONS
and PROJECTS where there is an entry in the join table. This query works as expected when
using MySQL.
> Here's the query:
> SELECT UNBOUND_E.PERSONID, UNBOUND_P.PROJID 
> FROM applicationidentity0.DEPARTMENTS THIS, 
>      applicationidentity0.PERSONS UNBOUND_E, 
>      applicationidentity0.PROJECTS UNBOUND_P 
> WHERE EXISTS ( 
>     SELECT 1 FROM applicationidentity0.PERSONS THIS_EMPLOYEES_E 
>     WHERE EXISTS ( 
>         SELECT 1 FROM applicationidentity0.PROJECT_MEMBER THIS_EMPLOYEES_E_PROJECTS_P

>         WHERE THIS_EMPLOYEES_E_PROJECTS_P."MEMBER" = THIS_EMPLOYEES_E.PERSONID 
>         AND THIS_EMPLOYEES_E_PROJECTS_P."MEMBER" = THIS_EMPLOYEES_E.PERSONID 
>         AND THIS_EMPLOYEES_E.DEPARTMENT = THIS.ID 
>         AND THIS_EMPLOYEES_E.DEPARTMENT = THIS.ID 
>         AND UNBOUND_P.PROJID = THIS_EMPLOYEES_E_PROJECTS_P.PROJID 
>         AND UNBOUND_E.PERSONID = THIS_EMPLOYEES_E.PERSONID) 
>     );
> PERSONID   |PROJID     
> -----------------------
> 3          |1          
> 5          |3          
> 4          |3          
> 2          |1          
> 1          |1          
> 5 rows selected
> I'm expecting 7 rows to be returned here, one row for each row in the join table. 
> Here's the schema:
> CREATE TABLE departments (
>     ID INTEGER NOT NULL,
>     NAME VARCHAR(32) NOT NULL,
>     EMP_OF_THE_MONTH INTEGER,
>     COMPANYID INTEGER,
>     DISCRIMINATOR VARCHAR(255),
>     CONSTRAINT DEPTS_COMP_FK FOREIGN KEY (COMPANYID) REFERENCES companies,
>     CONSTRAINT DEPTS_PK PRIMARY KEY (ID)
> );
> CREATE TABLE persons (
>     PERSONID INTEGER NOT NULL,
>     FIRSTNAME VARCHAR(32) NOT NULL,
>     LASTNAME VARCHAR(32) NOT NULL,
>     MIDDLENAME VARCHAR(32),
>     BIRTHDATE TIMESTAMP NOT NULL,
>     ADDRID INTEGER,
>     STREET VARCHAR(64),
>     CITY VARCHAR(64),
>     STATE CHAR(2),
>     ZIPCODE CHAR(5),
>     COUNTRY VARCHAR(64),
>     HIREDATE TIMESTAMP,
>     WEEKLYHOURS REAL,
>     DEPARTMENT INTEGER,
>     FUNDINGDEPT INTEGER,
>     MANAGER INTEGER,
>     MENTOR INTEGER,
>     HRADVISOR INTEGER,
>     SALARY REAL,
>     WAGE REAL,
>     DISCRIMINATOR varchar(255) NOT NULL,
>     CONSTRAINT PERS_DEPT_FK FOREIGN KEY (DEPARTMENT) REFERENCES departments,
>     CONSTRAINT PERS_FUNDDEPT_FK FOREIGN KEY (FUNDINGDEPT) REFERENCES departments,
>     CONSTRAINT PERS_MANAGER_FK FOREIGN KEY (MANAGER) REFERENCES persons,
>     CONSTRAINT PERS_MENTOR_FK FOREIGN KEY (MENTOR) REFERENCES persons,
>     CONSTRAINT PERS_HRADVISOR_FK FOREIGN KEY (HRADVISOR) REFERENCES persons,
>     CONSTRAINT EMPS_PK PRIMARY KEY (PERSONID)
> );
> CREATE TABLE projects (
>     PROJID INTEGER NOT NULL,
>     NAME VARCHAR(32) NOT NULL,
>     BUDGET DECIMAL(11,2) NOT NULL,
>     DISCRIMINATOR VARCHAR(255),
>     CONSTRAINT PROJS_PK PRIMARY KEY (PROJID)
> );
> CREATE TABLE project_member (
>     PROJID INTEGER REFERENCES projects NOT NULL,
>     MEMBER INTEGER REFERENCES persons NOT NULL
> );
> ij> connect 'jdbc:derby:/Users/clr/apache/jdo/trunk/tck2/target/database/derby/jdotckdb';
> ij> set schema applicationidentity0;
> 0 rows inserted/updated/deleted
> ij> select * from persons;
> PERSONID   |FIRSTNAME                       |LASTNAME                        |MIDDLENAME
                     |BIRTHDATE                 |ADDRID     |STREET                      
                                   |CITY                                                 
          |STA&|ZIPC&|COUNTRY                                                    
    |HIREDATE                  |WEEKLYHOURS  |DEPARTMENT |FUNDINGDEPT|MANAGER    |MENTOR 
   |HRADVISOR  |SALARY       |WAGE         |DISCRIMINATOR                                
                                                                                  
> -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> 1          |emp1First                       |emp1Last                        |emp1Middle
                     |1970-06-09 21:00:00.0     |NULL       |NULL                        
                                   |NULL                                                 
          |NULL|NULL |NULL                                                            |1998-12-31
21:00:00.0     |40.0         |NULL       |NULL       |NULL       |NULL       |NULL       |20000.0
     |NULL         |org.apache.jdo.tck.pc.company.FullTimeEmployee                       
                                                          
> 2          |emp2First                       |emp2Last                        |emp2Middle
                     |1975-12-21 21:00:00.0     |NULL       |NULL                        
                                   |NULL                                                 
          |NULL|NULL |NULL                                                            |2003-06-30
21:00:00.0     |40.0         |NULL       |NULL       |NULL       |NULL       |NULL       |10000.0
     |NULL         |org.apache.jdo.tck.pc.company.FullTimeEmployee                       
                                                          
> 3          |emp3First                       |emp3Last                        |emp3Middle
                     |1972-09-04 21:00:00.0     |NULL       |NULL                        
                                   |NULL                                                 
          |NULL|NULL |NULL                                                            |2002-08-14
21:00:00.0     |19.0         |NULL       |NULL       |NULL       |NULL       |NULL       |NULL
        |15.0         |org.apache.jdo.tck.pc.company.PartTimeEmployee                    
                                                             
> 4          |emp4First                       |emp4Last                        |emp4Middle
                     |1973-09-05 21:00:00.0     |NULL       |NULL                        
                                   |NULL                                                 
          |NULL|NULL |NULL                                                            |2001-04-14
21:00:00.0     |0.0          |NULL       |NULL       |NULL       |NULL       |NULL       |NULL
        |13.0         |org.apache.jdo.tck.pc.company.PartTimeEmployee                    
                                                             
> 5          |emp5First                       |emp5Last                        |emp5Middle
                     |1962-07-04 21:00:00.0     |NULL       |NULL                        
                                   |NULL                                                 
          |NULL|NULL |NULL                                                            |1998-08-14
21:00:00.0     |0.0          |NULL       |NULL       |NULL       |NULL       |NULL       |45000.0
     |NULL         |org.apache.jdo.tck.pc.company.FullTimeEmployee                       
                                                          
> 5 rows selected
> ij> select * from projects;
> PROJID     |NAME                            |BUDGET       |DISCRIMINATOR            
                                                                                         
            
> -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> 1          |orange                          |2500000.99   |org.apache.jdo.tck.pc.company.Project
                                                                                         

> 2          |blue                            |50000.00     |org.apache.jdo.tck.pc.company.Project
                                                                                         

> 3          |green                           |2000.99      |org.apache.jdo.tck.pc.company.Project
                                                                                         

> 3 rows selected
> ij> select * from project_member;
> PROJID     |MEMBER     
> -----------------------
> 2          |3          
> 1          |3          
> 2          |2          
> 3          |5          
> 3          |4          
> 1          |2          
> 1          |1          
> 7 rows selected

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