alter check constraint enforceability

syntax: ALTER TABLE ALTER CONSTRAINT [NOT] ENFORCED

context: https://git.postgresql.org/cgit/postgresql.git/commit/?id=ca87c415e2fccf81cec6fd45698dde9fae0ab570
discussion: https://postgr.es/m/CACJufxHCh_FU-FsEwsCvg9mN6-5tzR6H9ntn+0KUgTCaerDOmg@mail.gmail.com

Author: jianhe-fun

doc/src/sgml/ref/alter_table.sgml

@@ -569,8 +569,8 @@ WITH ( MODULUS <replaceable class="parameter">numeric_literal</replaceable>, REM
     <listitem>
      <para>
       This form alters the attributes of a constraint that was previously
-      created. Currently only foreign key constraints may be altered in
-      this fashion, but see below.
+      created. Currently <literal>FOREIGN KEY</literal> and
+      <literal>CHECK</literal> constraints may be altered in this fashion, but see below.
      </para>
     </listitem>
    </varlistentry>

src/backend/commands/tablecmds.c

@@ -404,6 +404,9 @@ static bool ATExecAlterConstrEnforceability(List **wqueue, ATAlterConstraint *cm
 											Oid ReferencedParentUpdTrigger,
 											Oid ReferencingParentInsTrigger,
 											Oid ReferencingParentUpdTrigger);
+static bool ATExecAlterCheckConstrEnforceability(List **wqueue, ATAlterConstraint *cmdcon,
+												 Relation conrel, HeapTuple contuple,
+												 bool recurse, bool recursing, LOCKMODE lockmode);
 static bool ATExecAlterConstrDeferrability(List **wqueue, ATAlterConstraint *cmdcon,
 										   Relation conrel, Relation tgrel, Relation rel,
 										   HeapTuple contuple, bool recurse,
@@ -422,6 +425,9 @@ static void AlterConstrEnforceabilityRecurse(List **wqueue, ATAlterConstraint *c
 											 Oid ReferencedParentUpdTrigger,
 											 Oid ReferencingParentInsTrigger,
 											 Oid ReferencingParentUpdTrigger);
+static void AlterCheckConstrEnforceabilityRecurse(List **wqueue, ATAlterConstraint *cmdcon,
+												  Relation conrel, Oid conrelid,
+												  bool recurse, bool recursing, LOCKMODE lockmode);
 static void AlterConstrDeferrabilityRecurse(List **wqueue, ATAlterConstraint *cmdcon,
 											Relation conrel, Relation tgrel, Relation rel,
 											HeapTuple contuple, bool recurse,
@@ -12181,7 +12187,7 @@ GetForeignKeyCheckTriggers(Relation trigrel,
  *
  * Update the attributes of a constraint.
  *
- * Currently only works for Foreign Key and not null constraints.
+ * Currently works for Foreign Key, CHECK, and not null constraints.
  *
  * If the constraint is modified, returns its address; otherwise, return
  * InvalidObjectAddress.
@@ -12243,11 +12249,13 @@ ATExecAlterConstraint(List **wqueue, Relation rel, ATAlterConstraint *cmdcon,
 				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
 				 errmsg("constraint \"%s\" of relation \"%s\" is not a foreign key constraint",
 						cmdcon->conname, RelationGetRelationName(rel))));
-	if (cmdcon->alterEnforceability && currcon->contype != CONSTRAINT_FOREIGN)
+	if (cmdcon->alterEnforceability &&
+		(currcon->contype != CONSTRAINT_FOREIGN && currcon->contype != CONSTRAINT_CHECK))
 		ereport(ERROR,
-				(errcode(ERRCODE_WRONG_OBJECT_TYPE),
-				 errmsg("cannot alter enforceability of constraint \"%s\" of relation \"%s\"",
-						cmdcon->conname, RelationGetRelationName(rel))));
+				errcode(ERRCODE_WRONG_OBJECT_TYPE),
+				errmsg("cannot alter enforceability of constraint \"%s\" of relation \"%s\"",
+						cmdcon->conname, RelationGetRelationName(rel)),
+				errhint("Only foreign key and check constraints can change enforceability"));
 	if (cmdcon->alterInheritability &&
 		currcon->contype != CONSTRAINT_NOTNULL)
 		ereport(ERROR,
@@ -12349,16 +12357,20 @@ ATExecAlterConstraintInternal(List **wqueue, ATAlterConstraint *cmdcon,
 	 * enforceability, we don't need to explicitly update multiple entries in
 	 * pg_trigger related to deferrability.
 	 *
-	 * Modifying enforceability involves either creating or dropping the
-	 * trigger, during which the deferrability setting will be adjusted
+	 * Modifying foreign key enforceability involves either creating or dropping
+	 * the trigger, during which the deferrability setting will be adjusted
 	 * automatically.
 	 */
-	if (cmdcon->alterEnforceability &&
+	if (cmdcon->alterEnforceability && currcon->contype == CONSTRAINT_FOREIGN &&
 		ATExecAlterConstrEnforceability(wqueue, cmdcon, conrel, tgrel,
 										currcon->conrelid, currcon->confrelid,
 										contuple, lockmode, InvalidOid,
 										InvalidOid, InvalidOid, InvalidOid))
 		changed = true;
+	else if (cmdcon->alterEnforceability && currcon->contype == CONSTRAINT_CHECK &&
+		ATExecAlterCheckConstrEnforceability(wqueue, cmdcon, conrel, contuple,
+											 recurse, false, lockmode))
+		changed = true;
 
 	else if (cmdcon->alterDeferrability &&
 			 ATExecAlterConstrDeferrability(wqueue, cmdcon, conrel, tgrel, rel,
@@ -12389,7 +12401,140 @@ ATExecAlterConstraintInternal(List **wqueue, ATAlterConstraint *cmdcon,
 }
 
 /*
- * Returns true if the constraint's enforceability is altered.
+ * Returns true if the CHECK constraint's enforceability is altered.
+ *
+ * Note that we must recurse even when trying to change a check constraint to
+ * not enforced if it is already not enforced, in case descendant constraints
+ * might be enforced and need to be changed to not enforced. Conversely, we
+ * should do nothing if a constraint is being set to enforced and is already
+ * enforced, as descendant constraints cannot be different in that case.
+ */
+static bool
+ATExecAlterCheckConstrEnforceability(List **wqueue, ATAlterConstraint *cmdcon,
+									 Relation conrel, HeapTuple contuple,
+									 bool recurse, bool recursing, LOCKMODE lockmode)
+{
+	Form_pg_constraint currcon;
+	Relation	rel;
+	bool		changed = false;
+	List	   *children = NIL;
+
+	/* Since this function recurses, it could be driven to stack overflow */
+	check_stack_depth();
+
+	Assert(cmdcon->alterEnforceability);
+
+	currcon = (Form_pg_constraint) GETSTRUCT(contuple);
+
+	Assert(currcon->contype == CONSTRAINT_CHECK);
+
+	rel = table_open(currcon->conrelid, lockmode);
+	if (currcon->conenforced != cmdcon->is_enforced)
+	{
+		AlterConstrUpdateConstraintEntry(cmdcon, conrel, contuple);
+		changed = true;
+	}
+
+	if (!cmdcon->is_enforced || changed)
+	{
+		/*
+		 * If we're recursing, the parent has already done this, so skip it.
+		 * Also, if the constraint is a NO INHERIT constraint, we shouldn't try
+		 * to look for it in the children.
+		*/
+		if (!recursing && !currcon->connoinherit)
+			children = find_all_inheritors(RelationGetRelid(rel),
+										   lockmode, NULL);
+
+		foreach_oid(childoid, children)
+		{
+			if (childoid == RelationGetRelid(rel))
+				continue;
+
+			/*
+			 * If we are told not to recurse, there had better not be any child
+			 * tables, because we can't change constraint enforceability on the
+			 * parent unless we have changed enforceability for all child.
+			*/
+			if (!recurse)
+				ereport(ERROR,
+						errcode(ERRCODE_INVALID_TABLE_DEFINITION),
+						errmsg("constraint must be altered on child tables too"));
+
+			AlterCheckConstrEnforceabilityRecurse(wqueue, cmdcon, conrel, childoid, false, true, lockmode);
+		}
+	}
+
+	/*
+	 * Tell Phase 3 to check that the constraint is satisfied by existing rows.
+	 * We do this only when alter the constraint from not enforced to enforced.
+	 */
+	if (rel->rd_rel->relkind == RELKIND_RELATION &&
+		cmdcon->is_enforced &&
+		!currcon->conenforced)
+	{
+		AlteredTableInfo *tab;
+		NewConstraint *newcon;
+		Datum		val;
+		char	   *conbin;
+
+		newcon = (NewConstraint *) palloc0(sizeof(NewConstraint));
+		newcon->name = pstrdup(NameStr(currcon->conname));
+		newcon->contype = CONSTR_CHECK;
+		val = SysCacheGetAttrNotNull(CONSTROID, contuple,
+									 Anum_pg_constraint_conbin);
+		conbin = TextDatumGetCString(val);
+		newcon->qual = expand_generated_columns_in_expr(stringToNode(conbin), rel, 1);
+
+		/* Find or create work queue entry for this table */
+		tab = ATGetQueueEntry(wqueue, rel);
+		tab->constraints = lappend(tab->constraints, newcon);
+	}
+
+	table_close(rel, NoLock);
+	return changed;
+}
+
+static void
+AlterCheckConstrEnforceabilityRecurse(List **wqueue, ATAlterConstraint *cmdcon,
+									  Relation conrel, Oid conrelid,
+									  bool recurse, bool recursing,
+									  LOCKMODE lockmode)
+{
+	SysScanDesc pscan;
+	HeapTuple	childtup;
+	ScanKeyData skey[3];
+
+	ScanKeyInit(&skey[0],
+				Anum_pg_constraint_conrelid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(conrelid));
+	ScanKeyInit(&skey[1],
+				Anum_pg_constraint_contypid,
+				BTEqualStrategyNumber, F_OIDEQ,
+				ObjectIdGetDatum(InvalidOid));
+	ScanKeyInit(&skey[2],
+				Anum_pg_constraint_conname,
+				BTEqualStrategyNumber, F_NAMEEQ,
+				CStringGetDatum(cmdcon->conname));
+
+	pscan = systable_beginscan(conrel, ConstraintRelidTypidNameIndexId, true,
+							   NULL, 3, skey);
+
+	if (!HeapTupleIsValid(childtup = systable_getnext(pscan)))
+		ereport(ERROR,
+				errcode(ERRCODE_UNDEFINED_OBJECT),
+				errmsg("constraint \"%s\" of relation \"%s\" does not exist",
+					   cmdcon->conname, get_rel_name(conrelid)));
+
+	ATExecAlterCheckConstrEnforceability(wqueue, cmdcon, conrel, childtup,
+										 recurse, recursing, lockmode);
+
+	systable_endscan(pscan);
+}
+
+/*
+ * Returns true if the FOREIGN KEY constraint's enforceability is altered.
  *
  * Depending on whether the constraint is being set to ENFORCED or NOT
  * ENFORCED, it creates or drops the trigger accordingly.

src/test/regress/expected/constraints.out

@@ -390,6 +390,59 @@ SELECT * FROM COPY_TBL;
  6 | OK            | 4
 (2 rows)
 
+--
+-- CHECK constraints
+-- ALTER TABLE ALTER CONSTRAINT [NOT] ENFORCED
+create table parted_ch_tbl(a int, constraint cc check (a > 10) not enforced, b int ) partition by range(a);
+create table parted_ch_tbl_1 partition of parted_ch_tbl for values from (0) to (10) partition by list(b);
+create table parted_ch_tbl_11 partition of parted_ch_tbl_1 for values in (0, 1);
+create table parted_ch_tbl_12 partition of parted_ch_tbl_1 for values in (2);
+create table parted_ch_tbl_2 partition of parted_ch_tbl for values from (10) to (20);
+alter table parted_ch_tbl_2 add constraint cc_2 check( a < 15) not enforced;
+insert into parted_ch_tbl values (1, 2), (9, 1), (16, 16);
+create view check_constraint_status as
+select  conname, conrelid::regclass, conenforced, convalidated
+from    pg_constraint
+where   conrelid::regclass::text ~* '^parted_ch' and contype = 'c'
+order by conrelid::regclass, conname;
+alter table parted_ch_tbl alter constraint cc not enforced; --no-op
+alter table parted_ch_tbl alter constraint cc enforced; --error
+ERROR:  check constraint "cc" of relation "parted_ch_tbl_11" is violated by some row
+delete from parted_ch_tbl where a = 1;
+alter table parted_ch_tbl alter constraint cc enforced; --error
+ERROR:  check constraint "cc" of relation "parted_ch_tbl_11" is violated by some row
+delete from parted_ch_tbl where a = 9;
+alter table parted_ch_tbl alter constraint cc enforced; --ok
+--check these CHECK constraint status
+select * from check_constraint_status;
+ conname |     conrelid     | conenforced | convalidated 
+---------+------------------+-------------+--------------
+ cc      | parted_ch_tbl    | t           | t
+ cc      | parted_ch_tbl_1  | t           | t
+ cc      | parted_ch_tbl_11 | t           | t
+ cc      | parted_ch_tbl_12 | t           | t
+ cc      | parted_ch_tbl_2  | t           | t
+ cc_2    | parted_ch_tbl_2  | f           | f
+(6 rows)
+
+alter table parted_ch_tbl_2 alter constraint cc_2 enforced; --error
+ERROR:  check constraint "cc_2" of relation "parted_ch_tbl_2" is violated by some row
+delete from parted_ch_tbl where a = 16;
+alter table parted_ch_tbl_2 alter constraint cc_2 enforced; --ok
+alter table parted_ch_tbl alter constraint cc not enforced; --ok
+--check these CHECK constraint status again
+select * from check_constraint_status;
+ conname |     conrelid     | conenforced | convalidated 
+---------+------------------+-------------+--------------
+ cc      | parted_ch_tbl    | f           | f
+ cc      | parted_ch_tbl_1  | f           | f
+ cc      | parted_ch_tbl_11 | f           | f
+ cc      | parted_ch_tbl_12 | f           | f
+ cc      | parted_ch_tbl_2  | f           | f
+ cc_2    | parted_ch_tbl_2  | t           | t
+(6 rows)
+
+drop table parted_ch_tbl;
 --
 -- Primary keys
 --
@@ -746,8 +799,10 @@ LINE 1: CREATE TABLE UNIQUE_NOTEN_TBL(i int UNIQUE NOT ENFORCED);
                                                    ^
 ALTER TABLE unique_tbl ALTER CONSTRAINT unique_tbl_i_key ENFORCED;
 ERROR:  cannot alter enforceability of constraint "unique_tbl_i_key" of relation "unique_tbl"
+HINT:  Only foreign key and check constraints can change enforceability
 ALTER TABLE unique_tbl ALTER CONSTRAINT unique_tbl_i_key NOT ENFORCED;
 ERROR:  cannot alter enforceability of constraint "unique_tbl_i_key" of relation "unique_tbl"
+HINT:  Only foreign key and check constraints can change enforceability
 -- can't make an existing constraint NOT VALID
 ALTER TABLE unique_tbl ALTER CONSTRAINT unique_tbl_i_key NOT VALID;
 ERROR:  constraints cannot be altered to be NOT VALID

src/test/regress/expected/inherit.out

@@ -1421,11 +1421,50 @@ order by 1, 2;
  p1_c3   | inh_check_constraint9  | f          |           2 | t           | t
 (38 rows)
 
+-- Tests for ALTER TABLE ALTER CONSTRAINT [NOT] ENFORCED
+alter table p1 drop constraint inh_check_constraint1;
+alter table p1_c1 drop constraint inh_check_constraint1;
+insert into p1_c1 values(-2);
+insert into p1_c3 values(-3);
+alter table only p1 alter constraint inh_check_constraint3 enforced; --error
+ERROR:  constraint must be altered on child tables too
+alter table only p1 alter constraint inh_check_constraint3 not enforced; --error
+ERROR:  constraint must be altered on child tables too
+alter table p1 alter constraint inh_check_constraint3 enforced; --error
+ERROR:  check constraint "inh_check_constraint3" of relation "p1_c1" is violated by some row
+delete from only p1_c1 where f1 = -2;
+alter table p1_c1 alter constraint inh_check_constraint3 enforced; --error
+ERROR:  check constraint "inh_check_constraint3" of relation "p1_c3" is violated by some row
+delete from only p1_c3 where f1 = -3;
+alter table p1 alter constraint inh_check_constraint3 enforced; --ok
+alter table p1 alter constraint inh_check_constraint3 not enforced; --ok
+select  conname, conenforced, convalidated, conrelid::regclass
+from    pg_constraint
+where   conname = 'inh_check_constraint3' and contype = 'c'
+order by conrelid::regclass::text collate "C";
+        conname        | conenforced | convalidated | conrelid 
+-----------------------+-------------+--------------+----------
+ inh_check_constraint3 | f           | f            | p1
+ inh_check_constraint3 | f           | f            | p1_c1
+ inh_check_constraint3 | f           | f            | p1_c2
+ inh_check_constraint3 | f           | f            | p1_c3
+(4 rows)
+
 drop table p1 cascade;
 NOTICE:  drop cascades to 3 other objects
 DETAIL:  drop cascades to table p1_c1
 drop cascades to table p1_c2
 drop cascades to table p1_c3
+--for "no inherit" check constraint, it will not recurse to child table
+create table p1(f1 int constraint p1_a_check check (f1 > 0) no inherit not enforced);
+create table p1_c1(f1 int constraint p1_a_check check (f1 > 0) not enforced);
+alter table p1_c1 inherit p1;
+insert into p1_c1 values(-11);
+alter table p1 alter constraint p1_a_check enforced; --ok
+alter table p1_c1 alter constraint p1_a_check enforced; --error
+ERROR:  check constraint "p1_a_check" of relation "p1_c1" is violated by some row
+drop table p1 cascade;
+NOTICE:  drop cascades to table p1_c1
 --
 -- Similarly, check the merging of existing constraints; a parent constraint
 -- marked as NOT ENFORCED can merge with an ENFORCED child constraint, but the
@@ -1434,6 +1473,25 @@ drop cascades to table p1_c3
 create table p1(f1 int constraint p1_a_check check (f1 > 0) not enforced);
 create table p1_c1(f1 int constraint p1_a_check check (f1 > 0) enforced);
 alter table p1_c1 inherit p1;
+insert into p1 values(-1); --ok
+insert into p1_c1 values(-1); --error
+ERROR:  new row for relation "p1_c1" violates check constraint "p1_a_check"
+DETAIL:  Failing row contains (-1).
+alter table p1 alter constraint p1_a_check enforced; --error
+ERROR:  check constraint "p1_a_check" of relation "p1" is violated by some row
+truncate p1;
+alter table p1 alter constraint p1_a_check enforced; --ok
+alter table p1 alter constraint p1_a_check not enforced; --ok
+select  conname, conenforced, convalidated, conrelid::regclass
+from    pg_constraint
+where   conname = 'p1_a_check' and contype = 'c'
+order by conrelid::regclass::text collate "C";
+  conname   | conenforced | convalidated | conrelid 
+------------+-------------+--------------+----------
+ p1_a_check | f           | f            | p1
+ p1_a_check | f           | f            | p1_c1
+(2 rows)
+
 drop table p1 cascade;
 NOTICE:  drop cascades to table p1_c1
 create table p1(f1 int constraint p1_a_check check (f1 > 0) enforced);