Hello
A customer of ours was taken by surprise by a change in Postgres 10 on a
trial upgrade from 9.6. They were using sequences from SERIAL columns a
little unorthodoxly, and their stuff stopped working: essentially, they
hacked the default expression so that it'd automatically use negative
numbers when the sequence reached INT_MAX. Since pg10 changed sequences
to stop emitting values at that point, it raised an error rather than
emit the negative numbers.
(In 9.6 and prior, the sequence would emit values past INT_MAX; it was
the column that raised the error. In pg10 things were changed so that
it is now the sequence that raises the error.)
My proposal now is to document this issue in the Postgres 10 release
notes. "It's a little late for that!" I hear you say, but keep this in
mind: many users have *not* yet upgraded to 10, and they'll keep doing
it for years to come still. So I disagree that now is too late. We
failed to warn people that already upgraded, but we're still on time to
alert people yet to upgrade.
I attach both the patch and a screenshot to show how minor the visual
effect of the change is.
(If people hate this, another option is to make it a separate bullet
point.)
--
Álvaro Herrera
diff --git a/doc/src/sgml/release-10.sgml b/doc/src/sgml/release-10.sgml
index 968ed866c2..f1dc816278 100644
--- a/doc/src/sgml/release-10.sgml
+++ b/doc/src/sgml/release-10.sgml
@@ -4717,6 +4717,13 @@ Branch: REL_10_STABLE [5159626af] 2017-11-03 14:14:16
-0400
</para>
<para>
+ Also, sequences created for <literal>SERIAL</literal> columns now
+ generate positive 32-bit wide values rather than 64-bit, as they
+ used to. (This has no visible effect if the values are just stored in
+ the column.)
+ </para>
+
+ <para>
The output of <application>psql</application>'s <command>\d</command>
command for a
sequence has been redesigned, too.
</para>
