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Fix PG 17 [NOT] NULL optimization bug for domains

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A PG 17 optimization allowed columns with NOT NULL constraints to skip
table scans for IS NULL queries, and to skip IS NOT NULL checks for IS
NOT NULL queries.  This didn't work for domain types, since domain types
don't follow the IS NULL/IS NOT NULL constraint logic.  To fix, disable
this optimization for domains for PG 17+.

Reported-by: Jan Behrens

Diagnosed-by: Tom Lane

Discussion: https://postgr.es/m/Z37p0paENWWUarj-@momjian.us

Backpatch-through: 17
This commit is contained in:
Bruce Momjian 2025-04-07 21:33:42 -04:00
parent 039549d70f
commit 46b4ba533c
2 changed files with 16 additions and 1 deletions
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3
doc/src/sgml/ref/create_domain.sgml
View File

@ -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

14
src/backend/optimizer/plan/initsplan.c
View File

@ -3109,6 +3109,13 @@ 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);
}
@ -3167,6 +3174,13 @@ 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);
}