Обсуждение: changes sequences to unique
I have a sequence that I 'thought' was providing unique numbers but is not. Is there someway to turn on unique-ness? Should I reload after adding unique to the sequence? Any other thoughts on digging my way out of the problem? Thanks in advance! -- Dave Stokes dave@greatgeek.com 817 329 9317
On Wed, 6 Jun 2001, Dave Stokes wrote: > I have a sequence that I 'thought' was providing unique numbers but is > not. Is there someway to turn on unique-ness? Should I reload after > adding unique to the sequence? Any other thoughts on digging my way out > of the problem? They should provide unique numbers. You could get non-unique values in a column with a sequence default if you manually insert values (the sequence wouldn't know about these). Can you give a sequence of events from a blank start to replicate what you're seeing?
Dave Stokes <dave@greatgeek.com> writes:
> I have a sequence that I 'thought' was providing unique numbers but is
> not. Is there someway to turn on unique-ness?
Huh? nextval() should always produce unique values (unless the sequence
wraps around, of course).
regards, tom lane
How did you conclude that it doesn't provide unique numbers? A sequence gives unique values by definition (unless you allowit to cycle and you actually wrapped around the 2.1billion boundary) cheers, thalis On Wed, 6 Jun 2001, Dave Stokes wrote: > I have a sequence that I 'thought' was providing unique numbers but is > not. Is there someway to turn on unique-ness? Should I reload after > adding unique to the sequence? Any other thoughts on digging my way out > of the problem? > > Thanks in advance! > -- > > Dave Stokes > dave@greatgeek.com > 817 329 9317 > > > ---------------------------(end of broadcast)--------------------------- > TIP 2: you can get off all lists at once with the unregister command > (send "unregister YourEmailAddressHere" to majordomo@postgresql.org) >
>Huh? nextval() should always produce unique values (unless the sequence >wraps around, of course). What about explicitly overruling a sequence by INSERTing a specific value, when it is not a primary key or defined as serial, but a manual sequence? Stefan -- I don't find it hard to meet expenses. They're everywhere!
dave@greatgeek.com (Dave Stokes) schreef: >I have a sequence that I 'thought' was providing unique numbers but is >not. Is there someway to turn on unique-ness? Sequences are documented on http://www.postgresql.org/users-lounge/docs/7.1/reference/sql-createsequence.html The numbers may not be unique if: - there are already values in the column that conflict with numbers (to be) generated by the sequence - it was created with "cycle" and it cycles - values are inserted into the column that have not been generated by the sequence - there is more than one sequence inserting values into the column - there is a trigger that interferes - ... >Should I reload after adding unique to the sequence? I'm not sure what you mean by that. -- Vriendelijke groet, René Pijlman <rpijlman@spamcop.net> Wat wil jij leren? http://www.leren.nl/
schweinsaug@crosswinds.net (Stefan Huber) schreef: >>Huh? nextval() should always produce unique values (unless the sequence >>wraps around, of course). > >What about explicitly overruling a sequence by INSERTing a specific value, >when it is not a primary key or defined as serial, but a manual sequence? Then the sequence will still produce unique values. Its just the database column that contains a duplicate :-) -- Vriendelijke groet, René Pijlman <rpijlman@spamcop.net> Wat wil jij leren? http://www.leren.nl/