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https://issues.apache.org/jira/browse/DERBY-3301?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12560462#action_12560462
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Bryan Pendleton commented on DERBY-3301:
----------------------------------------
Hi Thomas, thanks for having a look at this.
I agree with your analysis of that portion of the query plan: there are
7 total rows that are seen in the project_employees table, but they
are being organized into 3 hash buckets based on the projid field.
The rows in the table have projid values 101, 102, and 103, so this seems ok.
What seems to be happening to me is that we are "collapsing" the
results. The actual values that the query returns (with the current trunk) are:
EMPID |PROJID
-----------------------
13 |101
13 |102
15 |103
Note that we are getting *one* of the employees for *each* of the 3 projects,
whereas I think Craig expects us to be fetching *all* of the employees for
*each* of the projects.
I suspect this means that the flattening of the exists queries was performed
incorrectly, but beyond that I don't have anything brilliant to say. I looked at
some of this logic when I was studying DERBY-3033, but I don't think that
issue is extremely relevant to this issue.
Still, you might spend some time stepping through FromList.preprocess()
and FromList.flattenFromTables() for the query in question, and see if
you notice any logic that seems particularly relevant for this query.
> 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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