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From "Edwin Lukaweski" <serj...@rogers.com>
Subject Re: finding unique keys
Date Fri, 15 Sep 2006 15:39:31 GMT
Thanks for all the feed back!!!

Some answers:

    1) I am using DB2 for z/OS version 7

    2) Yes, UUID's are by definition 'universally unique', excpept whe two 
are gengerated, say by two different JVMs,  within the same millisecond. 
The, they turn out to be duplicates.

    3) I like the idea of doing an optimistic INSERT. I have always had 
trouble figuring which sql code to look for that represents this situation. 
As best I can tell, it is SQLCODE 803. So, if I see this code in an 
exception, loop again, otherwise throw a real sqlexception.

What do you think?

thanks,
Edwin

----- Original Message ----- 
From: "Larry Meadors" <lmeadors@apache.org>
To: <user-java@ibatis.apache.org>
Sent: Friday, September 15, 2006 11:03 AM
Subject: Re: finding unique keys


> +1 ;-)
>
> Larry
>
>
> On 9/15/06, Jeff Butler <jeffgbutler@gmail.com> wrote:
>>
>> Some thoughts...
>>
>> 1. Aren't UUID's "universally unique" by definition?  Are you sure you 
>> need
>> to do this?
>>
>> 2. Table locking is almost always a bad idea.  I had a similar situation 
>> to
>> yours in that past, and decided to take the optomistic route, meaning...
>>
>> - generate the key
>> - insert the record
>> - if the insert blows because of a duplicate key, then generate a new key
>> and try again
>>
>> Since the likelihood of generating a duplicate UUID should be very low, 
>> this
>> approcah will work in the vast majority of cases.
>>
>>
>> Jeff Butler
>>
>>
>>
>>
>> On 9/15/06, Edwin Lukaweski <serjann@rogers.com> wrote:
>> > Thanks for the answer.
>> >
>> >    I am stuck with an existing table definition, in a schema, that I
>> cannot
>> > modify at this point due to being in production.
>> >
>> >    So, this is the best method I can come up with.
>> >
>> >    also....now you have tweaked my curiosity. In addition to the advice 
>> > I
>> > am seeking, it I could alter the table definition to use some form of
>> > auto-increment, how would I retrieve the generated value in iBatis?
>> >
>> >    So.....I now have two questions.
>> >
>> > thanks,
>> > Ediwn
>> >
>> > ----- Original Message -----
>> > From: "Larry Meadors" < lmeadors@apache.org>
>> > To: <user-java@ibatis.apache.org>
>> > Sent: Friday, September 15, 2006 10:14 AM
>> > Subject: Re: finding unique keys
>> >
>> >
>> > > One question: Why not just let the database do it and have it tell 
>> > > you
>> > > the generated key?
>> > >
>> > > Larry
>> > >
>> > >
>> > > On 9/15/06, Edwin Lukaweski <serjann@rogers.com> wrote:
>> > >>
>> > >>
>> > >> Hi:
>> > >>
>> > >>     I have a situation for which I need some advice while using 
>> > >> iBatis.
>> > >>
>> > >>     What I would like to do is:
>> > >>
>> > >>     1) generate a unique UUID style value in my Java program
>> > >>
>> > >>     2) lock a table, say tabxx
>> > >>
>> > >>     3) SELECT on the table to see if the UUID exists as a key
>> > >>
>> > >>     4) if so, add 1 to the key and go to step 3
>> > >>
>> > >>     5) if the key does NOT exist, insert the record
>> > >>
>> > >>     6) unlock the table
>> > >>
>> > >>     Can anyone get me advice as to how to do this with iBatis?
>> > >>
>> > >> Thanks, very musch, in advance
>> > >>
>> > >> Edwin
>> > >>
>> > >
>> >
>> >
>> >
>>
>>
> 



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