David Fetter presumably uttered the following on 04/07/05 20:16:
On Thu, Apr 07, 2005 at 07:59:52PM -0400, Matthew Terenzio wrote:
I'm noticing that a sequence is advancing even if the insertion fails. Is this weird or expected?
It's expected. Sequences are guaranteed to generate unique IDs. These happen to be an increasing sequence of integers, but there is no attempt to make this a gap-free sequence, and your apps should not depend on the actual value of said ID.
I assume by "not depend on the actual value" that one should not assume that the next value will be one increment higher than the current highest value in the table; because it is guaranteed to be unique, I would think it to be an excellent way to assign a customer id, for example, which can then be referenced (foreign key, etc) by other tables after a new record is added. Unless there is some other reason one should not use a sequence value as any type of identifier?
Sven
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TIP 9: the planner will ignore your desire to choose an index scan if your
joining column's datatypes do not match
