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Re: Retrieving last InsertedID : INSERT... RETURNING safe ?

From: "Heikki Linnakangas" <heikki(at)enterprisedb(dot)com>
To: "Dave Cramer" <pg(at)fastcrypt(dot)com>
Cc: "Paul Tomblin" <ptomblin(at)gmail(dot)com>,<pgsql-jdbc(at)postgresql(dot)org>
Subject: Re: Retrieving last InsertedID : INSERT... RETURNING safe ?
Date: 2008-02-20 13:14:00
Message-ID: 47BC2798.9010300@enterprisedb.com (view raw or flat)
Thread:
Lists: pgsql-jdbc
Dave Cramer wrote:
> 
> On 20-Feb-08, at 7:19 AM, Paul Tomblin wrote:
> 
>> Dave Cramer wrote:
>>>> Well, that other solution is dangerous in case multiple inserts
>>>> to that table are done concurrently; a quite common usage pattern
>>>> with java web applications handling multiple HTTP requests with
>>>> concurrent java threads..
>>>>
>>> No it is not dangerous. It is the right way to do it. There is 
>>> absolutely no danger in using currval in this manner.
>>
>> Unless you have autocommit on.
>>
> I was going to say there are absolutely no situations where this is not 
> true, however in your case autocommit or not it doesn't matter.
> You have a single connection for the entire application and asynchronous 
> events using that connection. Autocommit or not it will not work with 
> currval.
> 
> In your case you must use nextval before doing the insert.

Now you lost me. By asynchronous events, do you mean NOTIFY/LISTEN? What 
exactly is the scenario you're talking about?

One problematic scenario for nextval+currval is an INSERT trigger that 
calls nextval() behind your back, but you can fool any method with a 
trigger if you really want to.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com

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