On 20.03.24 12:22, Dean Rasheed wrote:
Hmm, for CHECK constraints, the ALTER DOMAIN syntax for adding a
constraint is the same as for CREATE DOMAIN, but that's not the case
for NOT NULL constraints. So, for example, these both work:
CREATE DOMAIN d AS int CONSTRAINT c1 CHECK (value > 0);
ALTER DOMAIN d ADD CONSTRAINT c2 CHECK (value < 10);
However, for NOT NULL constraints, the ALTER DOMAIN syntax differs
from the CREATE DOMAIN syntax, because it expects "NOT NULL" to be
followed by a column name. So the following CREATE DOMAIN syntax
works:
CREATE DOMAIN d AS int CONSTRAINT nn NOT NULL;
but the equivalent ALTER DOMAIN syntax doesn't work:
ALTER DOMAIN d ADD CONSTRAINT nn NOT NULL;
ERROR: syntax error at or near ";"
LINE 1: ALTER DOMAIN d ADD CONSTRAINT nn NOT NULL;
^
All the examples in the tests append "value" to this, presumably by
analogy with CHECK constraints, but it looks as though anything works,
and is simply ignored:
ALTER DOMAIN d ADD CONSTRAINT nn NOT NULL xxx; -- works
That doesn't seem particularly satisfactory. I think it should not
require (and reject) a column name after "NOT NULL".
Hmm. CREATE DOMAIN uses column constraint syntax, but ALTER DOMAIN uses
table constraint syntax. As long as you are only dealing with CHECK
constraints, there is no difference, but it shows up when using NOT NULL
constraint syntax. I agree that this is unsatisfactory. Attached is a
patch to try to sort this out.
Looking in the SQL spec, it seems to only mention adding CHECK
constraints to domains, so the option to add NOT NULL constraints
should probably be listed in the "Compatibility" section.
<canofworms>
A quick reading of the SQL standard suggests to me that the way we are
doing null handling in domain constraints is all wrong. The standard
says that domain constraints are only checked on values that are not
null. So both the handling of constraints using the CHECK syntax is
nonstandard and the existence of explicit NOT NULL constraints is an
extension. The CREATE DOMAIN reference page already explains why all of
this is a bad idea. Do we want to document all of that further, or
maybe we just want to rip out domain not-null constraints, or at least
not add further syntax for it?
</canofworms>
From 0bdc4944879670b7b53447833fa9f9b385eb0309 Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <pe...@eisentraut.org>
Date: Thu, 21 Mar 2024 12:15:11 +0100
Subject: [PATCH] WIP: Fix ALTER DOMAIN NOT NULL syntax
---
doc/src/sgml/ref/create_domain.sgml | 17 ++++++--
src/backend/parser/gram.y | 60 ++++++++++++++++++++++++++--
src/test/regress/expected/domain.out | 8 ++--
src/test/regress/sql/domain.sql | 8 ++--
4 files changed, 79 insertions(+), 14 deletions(-)
diff --git a/doc/src/sgml/ref/create_domain.sgml
b/doc/src/sgml/ref/create_domain.sgml
index 73f9f28d6cf..078bea8410d 100644
--- a/doc/src/sgml/ref/create_domain.sgml
+++ b/doc/src/sgml/ref/create_domain.sgml
@@ -24,9 +24,9 @@
CREATE DOMAIN <replaceable class="parameter">name</replaceable> [ AS ]
<replaceable class="parameter">data_type</replaceable>
[ COLLATE <replaceable>collation</replaceable> ]
[ DEFAULT <replaceable>expression</replaceable> ]
- [ <replaceable class="parameter">constraint</replaceable> [ ... ] ]
+ [ <replaceable class="parameter">domain_constraint</replaceable> [ ... ] ]
-<phrase>where <replaceable class="parameter">constraint</replaceable>
is:</phrase>
+<phrase>where <replaceable class="parameter">domain_constraint</replaceable>
is:</phrase>
[ CONSTRAINT <replaceable class="parameter">constraint_name</replaceable> ]
{ NOT NULL | NULL | CHECK (<replaceable
class="parameter">expression</replaceable>) }
@@ -190,7 +190,7 @@ <title>Parameters</title>
</variablelist>
</refsect1>
- <refsect1>
+ <refsect1 id="sql-createdomain-notes">
<title>Notes</title>
<para>
@@ -279,6 +279,17 @@ <title>Compatibility</title>
The command <command>CREATE DOMAIN</command> conforms to the SQL
standard.
</para>
+
+ <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
+ NULL)</literal>. However, per <xref linkend="sql-createdomain-notes"/>,
+ such constraints a best avoided in practice anyway.) The
+ <literal>NULL</literal> <quote>constraint</quote> is a
+ <productname>PostgreSQL</productname> extension (see also <xref
+ linkend="sql-createtable-compatibility"/>).
+ </para>
</refsect1>
<refsect1 id="sql-createdomain-see-also">
diff --git a/src/backend/parser/gram.y b/src/backend/parser/gram.y
index 39a801a1c38..391a708467e 100644
--- a/src/backend/parser/gram.y
+++ b/src/backend/parser/gram.y
@@ -522,7 +522,7 @@ static Node *makeRecursiveViewSelect(char *relname, List
*aliases, Node *query);
%type <vsetstmt> generic_set set_rest set_rest_more generic_reset reset_rest
SetResetClause FunctionSetResetClause
-%type <node> TableElement TypedTableElement ConstraintElem TableFuncElement
+%type <node> TableElement TypedTableElement ConstraintElem
DomainConstraintElem TableFuncElement
%type <node> columnDef columnOptions
%type <defelt> def_elem reloption_elem old_aggr_elem operator_def_elem
%type <node> def_arg columnElem where_clause where_or_current_clause
@@ -593,7 +593,7 @@ static Node *makeRecursiveViewSelect(char *relname, List
*aliases, Node *query);
%type <keyword> col_name_keyword reserved_keyword
%type <keyword> bare_label_keyword
-%type <node> TableConstraint TableLikeClause
+%type <node> DomainConstraint TableConstraint TableLikeClause
%type <ival> TableLikeOptionList TableLikeOption
%type <str> column_compression opt_column_compression
column_storage opt_column_storage
%type <list> ColQualList
@@ -4251,6 +4251,60 @@ ConstraintElem:
}
;
+/*
+ * DomainConstraint is separate from TableConstraint because the syntax for
+ * NOT NULL constraints is different. For table constraints, we need to
+ * accept a column name, but for domain constraints, we don't. (We could
+ * accept something like NOT NULL VALUE, but that seems weird.) CREATE DOMAIN
+ * (which uses ColQualList) has for a long time accepted NOT NULL without a
+ * column name, so it makes sense that ALTER DOMAIN (which uses
+ * DomainConstraint) does as well. None of these syntaxes are per SQL
+ * standard; we are just living with the bits of inconsistency that have built
+ * up over time.
+ */
+DomainConstraint:
+ CONSTRAINT name DomainConstraintElem
+ {
+ Constraint *n = castNode(Constraint,
$3);
+
+ n->conname = $2;
+ n->location = @1;
+ $$ = (Node *) n;
+ }
+ | DomainConstraintElem
{ $$ = $1; }
+ ;
+
+DomainConstraintElem:
+ CHECK '(' a_expr ')' ConstraintAttributeSpec
+ {
+ Constraint *n = makeNode(Constraint);
+
+ n->contype = CONSTR_CHECK;
+ n->location = @1;
+ n->raw_expr = $3;
+ n->cooked_expr = NULL;
+ processCASbits($5, @5, "CHECK",
+ NULL, NULL,
&n->skip_validation,
+
&n->is_no_inherit, yyscanner);
+ n->initially_valid =
!n->skip_validation;
+ $$ = (Node *) n;
+ }
+ | NOT NULL_P ConstraintAttributeSpec
+ {
+ Constraint *n = makeNode(Constraint);
+
+ n->contype = CONSTR_NOTNULL;
+ n->location = @1;
+ n->keys =
list_make1(makeString("value"));
+ /* no NOT VALID support yet */
+ processCASbits($3, @3, "NOT NULL",
+ NULL, NULL,
NULL,
+
&n->is_no_inherit, yyscanner);
+ n->initially_valid = true;
+ $$ = (Node *) n;
+ }
+ ;
+
opt_no_inherit: NO INHERIT
{ $$ = true; }
| /* EMPTY */
{ $$ = false; }
;
@@ -11493,7 +11547,7 @@ AlterDomainStmt:
$$ = (Node *) n;
}
/* ALTER DOMAIN <domain> ADD CONSTRAINT ... */
- | ALTER DOMAIN_P any_name ADD_P TableConstraint
+ | ALTER DOMAIN_P any_name ADD_P DomainConstraint
{
AlterDomainStmt *n =
makeNode(AlterDomainStmt);
diff --git a/src/test/regress/expected/domain.out
b/src/test/regress/expected/domain.out
index dc58793e3f5..bf5c34bfacf 100644
--- a/src/test/regress/expected/domain.out
+++ b/src/test/regress/expected/domain.out
@@ -805,20 +805,20 @@ create table domconnotnulltest
, col2 connotnull
);
insert into domconnotnulltest default values;
-alter domain connotnull add not null value; -- fails
+alter domain connotnull add not null; -- fails
ERROR: column "col1" of table "domconnotnulltest" contains null values
update domconnotnulltest set col1 = 5;
-alter domain connotnull add not null value; -- fails
+alter domain connotnull add not null; -- fails
ERROR: column "col2" of table "domconnotnulltest" contains null values
update domconnotnulltest set col2 = 6;
-alter domain connotnull add constraint constr1 not null value;
+alter domain connotnull add constraint constr1 not null;
select count(*) from pg_constraint where contypid = 'connotnull'::regtype and
contype = 'n';
count
-------
1
(1 row)
-alter domain connotnull add constraint constr1bis not null value; -- redundant
+alter domain connotnull add constraint constr1bis not null; -- redundant
select count(*) from pg_constraint where contypid = 'connotnull'::regtype and
contype = 'n';
count
-------
diff --git a/src/test/regress/sql/domain.sql b/src/test/regress/sql/domain.sql
index ae1b7fbf97a..ce0c2e3cbc2 100644
--- a/src/test/regress/sql/domain.sql
+++ b/src/test/regress/sql/domain.sql
@@ -477,16 +477,16 @@
);
insert into domconnotnulltest default values;
-alter domain connotnull add not null value; -- fails
+alter domain connotnull add not null; -- fails
update domconnotnulltest set col1 = 5;
-alter domain connotnull add not null value; -- fails
+alter domain connotnull add not null; -- fails
update domconnotnulltest set col2 = 6;
-alter domain connotnull add constraint constr1 not null value;
+alter domain connotnull add constraint constr1 not null;
select count(*) from pg_constraint where contypid = 'connotnull'::regtype and
contype = 'n';
-alter domain connotnull add constraint constr1bis not null value; -- redundant
+alter domain connotnull add constraint constr1bis not null; -- redundant
select count(*) from pg_constraint where contypid = 'connotnull'::regtype and
contype = 'n';
update domconnotnulltest set col1 = null; -- fails
--
2.44.0
