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Re: duplicate key value violates unique constraint

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On 3/7/20 11:29 AM, Ashkar Dev wrote:
Hi all,

how to fix a problem, suppose there is a table with id and username

if I set the id to bigint so the limit is 9223372036854775807
if I insert for example 3 rows
id    username
--    --------------
1     abc
2     def
3     ghi

if I delete all rows and insert one another it is like

id    username
--    --------------
4     jkl

So I am assuming id is of type bigserial or something that has a sequence behind it?



So it doesn't start again from non-available id 1, so what is needed to do to make the new inserts go into non-available id numbers?

If you are sequences then they do not go backwards:

https://www.postgresql.org/docs/12/sql-createsequence.html

"Because nextval and setval calls are never rolled back, sequence objects cannot be used if “gapless” assignment of sequence numbers is needed. It is possible to build gapless assignment by using exclusive locking of a table containing a counter; but this solution is much more expensive than sequence objects, especially if many transactions need sequence numbers concurrently."

If you want that to happen you will have to roll your own implementation.


--
Adrian Klaver
adrian.klaver@xxxxxxxxxxx





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