PM06925: A JPQL QUERY WHICH CONTAINS A COMPOUND PRIMARY KEY ONLY USES ONE OF THE PRIMARY KEYS

Fixes are available

APAR status

Closed as program error.

Error description

The following two JPQL queries are being issued:

1) query = "SELECT COUNT (DISTINCT e) FROM G2 e";
2) query = "SELECT COUNT (DISTINCT f1.g2) FROM F1 f1";

Where G2 contains a compound primary key (namely PK1 and
PK2), and F1 has a @ManyToOne relationship with G2.

These queries yield an incorrect count because the SQL is not
generated properly for the case where a compound primary key is
used.

Local fix

Problem summary

****************************************************************
* USERS AFFECTED:  All users of IBM &#130; &#174; WebSphere &#130; &#174; Applicatio
*                  Server V7.0.0 who make use of JPQL queries  *
*                  which contain the COUNT function and        *
*                  compound primary keys.                      *
****************************************************************
* PROBLEM DESCRIPTION: Count(Distinct e) in JPQL gives the     *
*                      wrong result when the id field is a     *
*                      compound primary key.                   *
****************************************************************
* RECOMMENDATION:                                              *
****************************************************************
The following two JPQL queries are being issued:

1) query = "SELECT COUNT (DISTINCT e) FROM G2 e";
2) query = "SELECT COUNT (DISTINCT f1.g2) FROM F1 f1";

Where G2 contains a compound primary key (namely PK1 and PK2),
and F1 has a @ManyToOne relationship with G2.

For the first query, the goal is to count all distinct G2.
However, this JPQL query results in an SQL as follows:

SELECT COUNT(DISTINCT t0.PK1) FROM G2 t0  optimize for 1 row

This is a problem because the SQL only takes into account the
primary key PK1, however, it should also use primary key PK2.

For the second query, the goal is to count the distinct G2
referenced by F1.  However, this JPQL query results in an SQL
as follows:

SELECT COUNT(DISTINCT t1.PK1) FROM F1 t0 INNER JOIN G2 t1 ON
t0.PK1 = t1.PK1 AND t0.PK2 = t1.PK2  optimize for 1 row

Again, this is wrong because PK2 is not taken into account.
Things are further complicated with this query given relation
navigation is being used.  That is, the query attempts to find
all distict G2 referenced by F1.

Problem conclusion

For the first query, code has been added to handle the case
where a compound primary key is used in a 'COUNT( DISTINCT )'.
To enable this code, a user must set the following openJPA
property in their persistence.xml file:

<property name="openjpa.jdbc.DBDictionary"
value="useWildCardForCount=true"/>


For the second query, the property of 'useWildCardForCount'
will not generate correct sql with the right result given
relation navigation is involved.  With this fix, limited
support for count(distinct compound key) will be supported
when count(compound primary key) appears in the projection
list. This projection list will have only one projection item,
that is, count, in it. OpenJPA will generate the following SQL:

(1)
String jpql = "SELECT COUNT (DISTINCT e) FROM G2 e";
generated SQL:
SELECT COUNT(*) FROM G2 t0

(2)
String jpql = "SELECT COUNT (DISTINCT f1.g2) FROM F1 f1";
generated SQL:
SELECT COUNT(*) FROM (SELECT DISTINCT G1.G1PK, G1.G2PK FROM F1
t0 INNER JOIN G2 t1 ON t0.G1PK = t1.G1PK AND t0.G2PK = t1.G2PK)

An UnsupportedException will be thrown in all other situations.

The fix for this APAR is currently targeted for inclusion
in Fix Pack 7.0.0.13 of WebSphere Application Server
version 7.0.0.  Please refer to the Recommended Updates
page for delivery information:
http://www.ibm.com/support/docview.wss?rs=180&uid=swg27004980

Temporary fix

Comments

APAR Information

APAR number
PM06925
Reported component name
WEBS APP SERV N
Reported component ID
5724H8800
Reported release
700
Status
CLOSED PER
PE
NoPE
HIPER
NoHIPER
Special Attention
NoSpecatt
Submitted date
2010-02-05
Closed date
2010-05-06
Last modified date
2010-07-19

APAR is sysrouted FROM one or more of the following:
APAR is sysrouted TO one or more of the following:

Fix information

Fixed component name
WEBS APP SERV N
Fixed component ID
5724H8800

Applicable component levels

R700 PSY
UP

[{"Business Unit":{"code":"BU053","label":"Cloud & Data Platform"},"Product":{"code":"SSEQTP","label":"WebSphere Application Server"},"Platform":[{"code":"PF025","label":"Platform Independent"}],"Version":"7.0","Line of Business":{"code":"LOB45","label":"Automation"}}]

Document Information

Modified date:
25 October 2021

Tips

PM06925: A JPQL QUERY WHICH CONTAINS A COMPOUND PRIMARY KEY ONLY USES ONE OF THE PRIMARY KEYS

Fixes are available

Subscribe

APAR status

Closed as program error.

Error description

Local fix

Problem summary

Problem conclusion

Temporary fix

Comments

APAR Information

APAR number

Reported component name

Reported component ID

Reported release

Status

PE

HIPER

Special Attention

Submitted date

Closed date

Last modified date

APAR is sysrouted FROM one or more of the following:

APAR is sysrouted TO one or more of the following:

Fix information

Fixed component name

Fixed component ID

Applicable component levels

R700 PSY

Document Information

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