How can one rollover a sequence back to zero after you delete records from a table with one such sequence.
I see it starting with the last value of the sequence inserted.
On 7/11/07, Tom Allison <tom@xxxxxxxxxxx> wrote:
On Jul 10, 2007, at 3:09 PM, Tom Lane wrote:
>
> "Harpreet Dhaliwal" < harpreet.dhaliwal01@xxxxxxxxx> writes:
>> Transaction 1 started, saw max(dig_id) = 30 and inserted new
>> dig_id=31.
>> Now the time when Transaction 2 started and read max(dig_id) it
>> was still 30
>> and by the time it tried to insert 31, 31 was already inserted by
>> Transaction 1 and hence the unique key constraint error.
>
> This is exactly why you're recommended to use sequences (ie serial
> columns) for generating IDs. Taking max()+1 does not work, unless
> you're willing to lock the whole table and throw away vast amounts of
> concurrency.
I wonder how SQL server is handling this? Are they locking the table?
I realize it's off-topic, but I'm still curious.
Sequences are your friend. they come in INT and BIGINT flavors, but
BIGINT is a lot of rows.
Can set set Sequences to automatically rollover back to zero?
