by abandoning the idea that it should say SERIAL in the dump. Instead,
dump serial sequences and column defaults just like regular ones.
Add a new backend command ALTER SEQUENCE OWNED BY to let pg_dump recreate
the sequence-to-column dependency that was formerly created "behind the
scenes" by SERIAL. This restores SERIAL to being truly "just a macro"
consisting of component operations that can be stated explicitly in SQL.
Furthermore, the new command allows sequence ownership to be reassigned,
so that old mistakes can be cleaned up.
Also, downgrade the OWNED-BY dependency from INTERNAL to AUTO, since there
is no longer any very compelling argument why the sequence couldn't be
dropped while keeping the column. (This forces initdb, to be sure the
right kinds of dependencies are in there.)
Along the way, add checks to prevent ALTER OWNER or SET SCHEMA on an
owned sequence; you can now only do this indirectly by changing the
owning table's owner or schema. This is an oversight in previous
releases, but probably not worth back-patching.
<replaceable class="parameter">colname</replaceable> integer DEFAULT nextval('<replaceable class="parameter">tablename</replaceable>_<replaceable class="parameter">colname</replaceable>_seq') NOT NULL
<replaceable class="parameter">colname</replaceable> integer NOT NULL DEFAULT nextval('<replaceable class="parameter">tablename</replaceable>_<replaceable class="parameter">colname</replaceable>_seq')
);
ALTER SEQUENCE <replaceable class="parameter">tablename</replaceable>_<replaceable class="parameter">colname</replaceable>_seq OWNED BY <replaceable class="parameter">tablename</replaceable>.<replaceable class="parameter">colname</replaceable>;
</programlisting>
Thus, we have created an integer column and arranged for its default
values to be assigned from a sequence generator. A <literal>NOT NULL</>
constraint is applied to ensure that a null value cannot be explicitly
inserted, either. In most cases you would also want to attach a
inserted, either. (In most cases you would also want to attach a
<literal>UNIQUE</> or <literal>PRIMARY KEY</> constraint to prevent
duplicate values from being inserted by accident, but this is
not automatic.
not automatic.) Lastly, the sequence is marked as <quote>owned by</>
the column, so that it will be dropped if the column or table is dropped.
The <literal>OWNED BY</literal> option causes the sequence to be
associated with a specific table column, such that if that column
(or its whole table) is dropped, the sequence will be automatically
dropped as well. The specified table must have the same owner and be in
the same schema as the sequence.
<literal>OWNED BY NONE</literal>, the default, specifies that there
is no such association.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
@ -300,11 +317,38 @@ END;
<command>CREATE SEQUENCE</command> conforms to the <acronym>SQL</acronym>
standard, with the following exceptions:
<itemizedlist>
<listitem><para>The standard's <literal>AS <data type></literal> expression is not supported.</para></listitem>
<listitem><para>Obtaining the next value is done using the <function>nextval()</> function instead of the standard's <command>NEXT VALUE FOR</command> expression.</para></listitem>
<listitem>
<para>
The standard's <literal>AS <data type></literal> expression is not
supported.
</para>
</listitem>
<listitem>
<para>
Obtaining the next value is done using the <function>nextval()</>
function instead of the standard's <command>NEXT VALUE FOR</command>
expression.
</para>
</listitem>
<listitem>
<para>
The <literal>OWNED BY</> clause is a <productname>PostgreSQL</>
Tom Lane
19 years ago