2009/10/30 Mark Morgan Lloyd <markMLl.pgsql-general@xxxxxxxxxxxxxxx>: >> On Fri, Oct 30, 2009 at 8:44 AM, Mark Morgan Lloyd >> <markMLl.pgsql-general@xxxxxxxxxxxxxxx> wrote: >>> >>> What is the "correct" behavior of a serial column when a table is created >>> with LIKE? The manual is silent on this. >>> >>> What appears to be happening with 8.2 is that the column in the new table >>> refers to the original sequence generator. >>> >>> -- >>> Mark Morgan Lloyd >>> markMLl .AT. telemetry.co .DOT. uk >>> >>> [Opinions above are the author's, not those of his employers or >>> colleagues] >>> >>> -- >>> Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) >>> To make changes to your subscription: >>> http://www.postgresql.org/mailpref/pgsql-general > > silly8888 wrote: >> In 8.4, the sequence value is copied only when INCLUDING DEFAULTS is >> specified. Otherwise, only the not null constraint is copied. I think >> this is the most reasonable behavior and I don't see why it should >> have been explicitly stated in the manual. > > I didn't say the sequence value, I said the sequence itself. After all the > normal usage will be where the "pattern" table is empty. > > In other words the newly-created table is not completely decoupled from the > pattern, the sequence is a shared resource and this is irrespective of any > including/excluding specification. > I can see why you wouldn't expect it to end up sharing the same sequence. If you were to manually create a sequence and wanted to use it on a column, you probably wouldn't bother using the SERIAL datatype, but use integer instead. So really since we know the first table has a datatype of SERIAL on one of its columns, we might instead wish to have it create a new implicit sequence instead of merely converting it to an INTEGER datatype and adding a default constraint to the same sequence as the original table. In theory, you could create a table and subsequently change the SERIAL column's default value to another sequence, but I imagine that this would be a very rare case since you wouldn't bother with the SERIAL datatype in the first place if you knew you were going to do that. I believe most people would expect a new implicit sequence to be created, but maybe a PostgreSQL "elder" could enlighten us further. Thom -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
