Subject Re: [firebird-support] violation of PRIMARY or UNIQUE KEY constraint
Author Ann Harrison
On Tue, Mar 15, 2016 at 8:04 AM, Tim Ward tdw@... [firebird-support] <> wrote:

Now, I seem to recall seeing somewhere that actually a primary key (and any other unique index?) is independent of transactions, so the following:

(1) Transaction A inserts record X
(2) Transaction B attempts to insert record X (having first checked that it doesn't exist, which it doesn't as far as transaction B is concerned, because transaction A hasn't committed yet)

results in the error.

Have I remembered this behaviour of primary keys correctly? Please could someone remind me where the documentation is if so?

On the documentation front, no, though it's probably in Helen's book, but your memory is correct.  When Firebird attempts to put
a new entry in the unique/primary key index on behalf of Transaction B, it notices that there's an entry for A and that A's transaction
is not committed.  Firebird causes B to wait for A to complete (unless it's no wait), then gets an error if A commits and succeeds
if A failed.

Good luck,