Re: Best approach for a "gap-less" sequence

Jorge Godoy wrote on 12.08.2006 01:33:
> I was trying to solve a problem on an old system and realized that there might
> be some better approach for doing what I need.
>
> We have some documents that need to be ordered sequentially and without gaps.
> I could use a sequence, but if the transaction fails then when I rollback the
> sequence will already have been incremented.
>
> So, today I have a control table and I acquire a SHARE ROW EXCLUSIVE lock to
> it, read the value, increase it, do what I need and then I COMMIT the
> transaction, ensuring that the sequence has no gaps.
>
> Is there a better way to guarantee that there will be no gaps in my sequence
> if something goes wrong with my transaction?

What do you do if a document gets deleted? Renumber the "following" documents so
that no gaps are present in the already used ids?

Thomas