helen or someone will reply later and tell me how wrong I am ;), but....

First, it isn't really possible for 2 users to execute the statement at
the *exact* same time, one has to come before the other... but anyway....

Generators operate outside of user transactions. Test it. A rollback
leaves the generator as it was whether you rollback or commit.
Therefore, it isn't possible for the same value to be returned if you
assume they are the only two statements going on. However, if there
were a third user such that the execution occurred in this manner....

user 1

SELECT GEN_ID(EXPORTLOCK_SEQ, -1)
FROM RDB$DATABASE;

user 2

SELECT GEN_ID(EXPORTLOCK_SEQ, 1)
FROM RDB$DATABASE

user 3

SELECT GEN_ID(EXPORTLOCK_SEQ, -1)
FROM RDB$DATABASE


then users 1 and 3 will get the same value.

Is this a possibility?






Peter Ypenburg wrote:

>Hi There,
>
>Is it possible for two users who run the following SQL at the exact same
>time (each in their own transaction) to get the same value back from a
>generator. The SQL is as follows:
>
>SELECT GEN_ID(EXPORTLOCK_SEQ, -1)
>FROM RDB$DATABASE
>
>Thanks.
>
>Peter Ypenburg
>AGM: Product Development
>Barloworld Optimus
>Tel +2711 286 1587 Fax +2711 286 1630 Cell +2782 789 9167
>www.barloworldoptimus.com
>
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