The INSERT statement conflicted with the FOREIGN KEY constraint(Not reproducible)

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The INSERT statement conflicted with the FOREIGN KEY constraint(Not reproducible)

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anki_bakshi

Posted Friday, August 14, 2009 3:59 PM

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We have one parent table:
Document (GID int identity(1,1),ParentName)

and two child tables, both having FOREIGN KEY(Document_GID) REFERENCES Document (GID)
1. DocumentChild1(Document_GID,Child1_name)
2. DocumentChild2(Document_GID,Child2_name)

Steps:
1. Lets say DocumentChild1 table has 'n' documents.
2. Then in a transaction we try to insert entries into DocumentChild2 from DocumentChild1.
Here, we get foreign key violation :
The INSERT statement conflicted with the FOREIGN KEY constraint "DocumentChild2_DOC_GID_FK".
The conflict occurred in database "VOL_ABC", table "Document", column 'GID'.

Also, we don't have any delete operation in Document table. But many insert operation into this table can be going on in parallel.
We saw this error once. Everything works fine when we reran the insert sql.

I am wondering, what could have caused this behavior. Definitely data exists in the Document table else insert into DocumentChild1 would have failed.

Let me know if you need more details.

Post #771369

Jack Corbett

Posted Monday, August 17, 2009 6:41 AM

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You aren't using nolock or SET ISOLATION LEVEL READ UNCOMMITTED are you?

Jack Corbett

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Post #771848

anki_bakshi

Posted Monday, August 17, 2009 2:11 PM

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My transaction isolation level is READ_COMMITTED and yes, I am using nolocks while reading data from DocumentChild1. But, I have verified that no one is changing(Insert/Update/Delete) data in the DocumentChild1 during that time. Also, I had sql profiler enable when we saw this error. The rowcount suggests that the correct number of records being read from DocumentChild1.

Thanks for your help.

Post #772248

anki_bakshi

Posted Monday, August 17, 2009 2:41 PM

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I am wondering do indexes on the table play part in this FK constraint violation error.
I have a unique index on DocumentChild2(Document_GID,Child2_name).

Post #772273

Jack Corbett

Posted Monday, August 17, 2009 2:59 PM

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anki_bakshi (8/17/2009)

I am wondering do indexes on the table play part in this FK constraint violation error.
I have a unique index on DocumentChild2(Document_GID,Child2_name).

Nope, you'd get a unique index/constraint violation error.

Was the FK on DocumentChild1 created AFTER there was data in the table? If to there could be "bad" data in the table if the constraint was created with the NOCHECK option

Post #772291

anki_bakshi

Posted Monday, August 17, 2009 5:44 PM

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No, the FK on DocumentChild1 was created at the time of table creation.

Can multiple asynchronous inserts in the Document table can cause this behavior? I mean may be the index page where the concerned GID is located is locked by the Insert sql as it is also inserting into the same page.

Post #772374

anki_bakshi

Posted Wednesday, August 19, 2009 12:14 PM

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Update:
We had a live meeting session with microsoft support where they have debugged this behavior. There is no resolution yet, and might be a bug on their side.

Post #773804

anki_bakshi

Posted Wednesday, October 28, 2009 11:57 AM

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Update: There is a bug in microsoft sql server's Hash Map join plan when it comes to # based temp tables.
To suppress this error(workaround given by Microsoft team): Include order by 1 clause - this will change the join plan.

For eg.
INSERT INTO MAIN_TABLE (DOC_ID_FK_TO_SOME_OTHER_TABLE, ANY_COLUMN)
SELECT DOC_ID_FK_TO_SOME_OTHER_TABLE, ANY_COLUMN
FROM #TEMP_TABLE -- This will sometimes throw FK violation which is not a --valid violation
ORDER BY 1 -- This suppresses the error

Post #810184

Jack Corbett

Posted Wednesday, October 28, 2009 12:01 PM

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Interesting. Thanks for posting the resolution even though it came months later.

Post #810192

anki_bakshi

Posted Tuesday, January 05, 2010 5:39 PM

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Here is KB article ( http://support.microsoft.com/kb/977100/ )explaining about the issue we have raised and possible workarounds in case anyone is interested.

Post #842507

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