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From "Tony Selke" <tony.se...@gmail.com>
Subject RE: Do not use <selectKey> with SCOPE_IDENTITY and MSSQL?
Date Tue, 18 Sep 2007 11:59:46 GMT
You still should be using SCOPE_IDENTITY() to get your inserted key values.
As mentioned, IDENT_CURRENT() will not restrain itself to the scope of the
procedure/trigger being executed and you still get the potential for race
conditions, etc.  Granted, it is a smaller chance than if you were using
@@IDENTITY because you are limiting yourself to one table instead of all
tables, but in a case of a heavily inserted table it is still a possibility
that should be avoided.

 

We ran into this same issue a few months back and we had to do the "insert,
set variable to SCOPE_IDENTITY, select variable back out to an int type
result class" batch method to get around the problem.  I would definitely
vote for an update to make iBATIS use this function (I would have done it
myself had we the slack int eh project schedule; isn't that always the
way?).

 

Tony

 

From: Clough, Samuel (USPC.PRG.Atlanta)
[mailto:Samuel_Clough@princetonrg.com] 
Sent: Tuesday, September 18, 2007 7:13 AM
To: user-cs@ibatis.apache.org
Subject: RE: Do not use <selectKey> with SCOPE_IDENTITY and MSSQL?

 

I wasn't aware of ident_current.  That seems like the best solution.

 

From: Sean Blakemore [mailto:sean.blakemore@gmail.com] 
Sent: Tuesday, September 18, 2007 7:10 AM
To: user-cs@ibatis.apache.org
Subject: Re: Do not use <selectKey> with SCOPE_IDENTITY and MSSQL?

 

The reason being that if for example you have a trigger which updates some
audit table when you perform an insert on an entity table, with @@IDENTITY
there is no scope and the returned identity will be /could be the new row in
the audit table and not the new row in the entity table. SCOPE_IDENTITY does
not have this problem, as the trigger would be out of scope of the current
session. The midground between the two is IDENT_CURRENT('TableName') which
like @@IDENTITY is not scoped to any session, however it is scoped to the
provided table, somewhat aleviating the risk of the audit trigger issue. 

Sean

On 9/18/07, Clough, Samuel (USPC.PRG.Atlanta)
<Samuel_Clough@princetonrg.com> wrote: 

Like the original email mentioned, wasn't there an issue with @@IDENTITY
that would make it somewhat unreliable?  I don't remember specifics, but
there was a reason I switched from it to SCOPE_IDENTITY a few years back.
Perhaps it was just as issue in an older version of MS SQL.

 

From: Gilles Bayon [mailto:ibatis.net@gmail.com] 
Sent: Tuesday, September 18, 2007 2:35 AM
To: user-cs@ibatis.apache.org
Subject: Re: Do not use <selectKey> with SCOPE_IDENTITY and MSSQL?

 

SCOPE_IDENTITY / @@IDENTITY
Returns the last identity value inserted into an identity column in the same
scope. 
A scope is a module: a stored procedure, trigger, function, or batch.
Therefore, two statements are in the same scope if they are in the same
stored procedure, function, or batch. 

SCOPE_IDENTITY and @@IDENTITY return the last identity values that are
generated in any table in the current session. 
However, SCOPE_IDENTITY returns values inserted only within the current
scope; @@IDENTITY is not limited to a specific scope. 

>From http://msdn2.microsoft.com/en-us/library/ms190315.aspx

So if you want to use the selectKey statement, use the @@IDENTITY.

If you want you can make an entry in the wiki
http://opensource.atlassian.com/confluence/oss/display/IBATIS/Home 

-- 
Cheers,
Gilles

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