Re: Fetching generated keys - Mailing list pgsql-jdbc

From Tom Lane
Subject Re: Fetching generated keys
Date
Msg-id 23790.1173134881@sss.pgh.pa.us
Whole thread Raw
In response to Re: Fetching generated keys  (Heikki Linnakangas <heikki@enterprisedb.com>)
List pgsql-jdbc
Heikki Linnakangas <heikki@enterprisedb.com> writes:
> Mike Clements wrote:
>> Up to now, we were selecting the current value of the sequence
>> immediately after the insert. I thought this was safe because
>> transactions should be isolated. But now I realize this could
>> potentially fail because the default transaction isolation is "read
>> committed". Thus if another connection inserts into the same table,
>> causing the sequence to increment, if it commits before we read the
>> sequence value, we might read the wrong value (the value as incremented
>> by the other transaction, not the value as it was for our own insert).

> You should use the lastval-function. It retrieves the last value
> returned in your connection. "SELECT lastval('sequence')"

I think you meant "currval".  In any case the point is that these are
session-local and so Mike's concern is unfounded.

            regards, tom lane

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