On Wed, Jan 8, 2025 at 04:24:34PM -0500, Tom Lane wrote:
> Bruce Momjian <[email protected]> writes:
> > I think this needs some serious research.
>
> We've discussed this topic before. The spec's definition of IS [NOT]
> NULL for composite values is bizarre to say the least. I think
> there's been an intentional choice to keep most NOT NULL checks
> "simple", that is we look at the overall value's isnull bit and
> don't probe any deeper than that.
>
> If the optimizations added in v17 changed existing behavior,
> I agree that's bad. We should probably fix it so that those
> are only applied when argisrow is false.
I have developed the attached patch using your argisrow suggestion which
fixes the test I posted. Is this something we should backpatch?
--
Bruce Momjian <[email protected]> https://momjian.us
EDB https://enterprisedb.com
Do not let urgent matters crowd out time for investment in the future.
diff --git a/doc/src/sgml/ref/create_domain.sgml b/doc/src/sgml/ref/create_domain.sgml
index ce555203486..c111285a69c 100644
--- a/doc/src/sgml/ref/create_domain.sgml
+++ b/doc/src/sgml/ref/create_domain.sgml
@@ -283,7 +283,8 @@ CREATE TABLE us_snail_addy (
<para>
The syntax <literal>NOT NULL</literal> in this command is a
<productname>PostgreSQL</productname> extension. (A standard-conforming
- way to write the same would be <literal>CHECK (VALUE IS NOT
+ way to write the same for non-composite data types would be
+ <literal>CHECK (VALUE IS NOT
NULL)</literal>. However, per <xref linkend="sql-createdomain-notes"/>,
such constraints are best avoided in practice anyway.) The
<literal>NULL</literal> <quote>constraint</quote> is a
diff --git a/src/backend/optimizer/plan/initsplan.c b/src/backend/optimizer/plan/initsplan.c
index 2cb0ae6d659..e291547112d 100644
--- a/src/backend/optimizer/plan/initsplan.c
+++ b/src/backend/optimizer/plan/initsplan.c
@@ -3100,6 +3100,13 @@ restriction_is_always_true(PlannerInfo *root,
if (nulltest->nulltesttype != IS_NOT_NULL)
return false;
+ /*
+ * Empty rows can appear NULL in some contexts and NOT NULL in others,
+ * so avoid this optimization for row expressions.
+ */
+ if (nulltest->argisrow)
+ return false;
+
return expr_is_nonnullable(root, nulltest->arg);
}
@@ -3149,6 +3156,13 @@ restriction_is_always_false(PlannerInfo *root,
if (nulltest->nulltesttype != IS_NULL)
return false;
+ /*
+ * Empty rows can appear NULL in some contexts and NOT NULL in others,
+ * so avoid this optimization for row expressions.
+ */
+ if (nulltest->argisrow)
+ return false;
+
return expr_is_nonnullable(root, nulltest->arg);
}
