Fix handling of inherited check constraints in ALTER COLUMN TYPE.

tglsfdc · tglsfdc · commit f43ca3c8945f · 2012-11-05T13:36:26.000-05:00
This case got broken in 8.4 by the addition of an error check that
complains if ALTER TABLE ONLY is used on a table that has children.
We do use ONLY for this situation, but it's okay because the necessary
recursion occurs at a higher level.  So we need to have a separate
flag to suppress recursion without making the error check.

Reported and patched by Pavan Deolasee, with some editorial adjustments by
me.  Back-patch to 8.4, since this is a regression of functionality that
worked in earlier branches.
diff --git a/src/backend/commands/tablecmds.c b/src/backend/commands/tablecmds.c
@@ -323,13 +323,15 @@ static void ATExecAddIndex(AlteredTableInfo *tab, Relation rel,
 			   IndexStmt *stmt, bool is_rebuild, LOCKMODE lockmode);
 static void ATExecAddConstraint(List **wqueue,
 					AlteredTableInfo *tab, Relation rel,
-				 Constraint *newConstraint, bool recurse, LOCKMODE lockmode);
+					Constraint *newConstraint, bool recurse, bool is_readd,
+					LOCKMODE lockmode);
 static void ATExecAddIndexConstraint(AlteredTableInfo *tab, Relation rel,
 						 IndexStmt *stmt, LOCKMODE lockmode);
 static void ATAddCheckConstraint(List **wqueue,
 					 AlteredTableInfo *tab, Relation rel,
 					 Constraint *constr,
-					 bool recurse, bool recursing, LOCKMODE lockmode);
+					 bool recurse, bool recursing, bool is_readd,
+					 LOCKMODE lockmode);
 static void ATAddForeignKeyConstraint(AlteredTableInfo *tab, Relation rel,
 						  Constraint *fkconstraint, LOCKMODE lockmode);
 static void ATExecDropConstraint(Relation rel, const char *constrName,
@@ -2560,6 +2562,7 @@ AlterTableGetLockLevel(List *cmds)
 			case AT_ColumnDefault:
 			case AT_ProcessedConstraint:		/* becomes AT_AddConstraint */
 			case AT_AddConstraintRecurse:		/* becomes AT_AddConstraint */
+			case AT_ReAddConstraint:			/* becomes AT_AddConstraint */
 			case AT_EnableTrig:
 			case AT_EnableAlwaysTrig:
 			case AT_EnableReplicaTrig:
@@ -3036,11 +3039,15 @@ ATExecCmd(List **wqueue, AlteredTableInfo *tab, Relation rel,
 			break;
 		case AT_AddConstraint:	/* ADD CONSTRAINT */
 			ATExecAddConstraint(wqueue, tab, rel, (Constraint *) cmd->def,
-								false, lockmode);
+								false, false, lockmode);
 			break;
 		case AT_AddConstraintRecurse:	/* ADD CONSTRAINT with recursion */
 			ATExecAddConstraint(wqueue, tab, rel, (Constraint *) cmd->def,
-								true, lockmode);
+								true, false, lockmode);
+			break;
+		case AT_ReAddConstraint:	/* Re-add pre-existing check constraint */
+			ATExecAddConstraint(wqueue, tab, rel, (Constraint *) cmd->def,
+								false, true, lockmode);
 			break;
 		case AT_AddIndexConstraint:		/* ADD CONSTRAINT USING INDEX */
 			ATExecAddIndexConstraint(tab, rel, (IndexStmt *) cmd->def, lockmode);
@@ -5235,7 +5242,8 @@ ATExecAddIndexConstraint(AlteredTableInfo *tab, Relation rel,
  */
 static void
 ATExecAddConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
-				  Constraint *newConstraint, bool recurse, LOCKMODE lockmode)
+					Constraint *newConstraint, bool recurse, bool is_readd,
+					LOCKMODE lockmode)
 {
 	Assert(IsA(newConstraint, Constraint));
 
@@ -5248,7 +5256,8 @@ ATExecAddConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
 	{
 		case CONSTR_CHECK:
 			ATAddCheckConstraint(wqueue, tab, rel,
-								 newConstraint, recurse, false, lockmode);
+								 newConstraint, recurse, false, is_readd,
+								 lockmode);
 			break;
 
 		case CONSTR_FOREIGN:
@@ -5300,11 +5309,18 @@ ATExecAddConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
  * AddRelationNewConstraints would normally assign different names to the
  * child constraints.  To fix that, we must capture the name assigned at
  * the parent table and pass that down.
+ *
+ * When re-adding a previously existing constraint (during ALTER COLUMN TYPE),
+ * we don't need to recurse here, because recursion will be carried out at a
+ * higher level; the constraint name issue doesn't apply because the names
+ * have already been assigned and are just being re-used.  We need a separate
+ * "is_readd" flag for that; just setting recurse=false would result in an
+ * error if there are child tables.
  */
 static void
 ATAddCheckConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
 					 Constraint *constr, bool recurse, bool recursing,
-					 LOCKMODE lockmode)
+					 bool is_readd, LOCKMODE lockmode)
 {
 	List	   *newcons;
 	ListCell   *lcon;
@@ -5363,6 +5379,13 @@ ATAddCheckConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
 	if (newcons == NIL)
 		return;
 
+	/*
+	 * Also, in a re-add operation, we don't need to recurse (that will be
+	 * handled at higher levels).
+	 */
+	if (is_readd)
+		return;
+
 	/*
 	 * Propagate to children as appropriate.  Unlike most other ALTER
 	 * routines, we have to do this one level of recursion at a time; we can't
@@ -5394,7 +5417,7 @@ ATAddCheckConstraint(List **wqueue, AlteredTableInfo *tab, Relation rel,
 
 		/* Recurse to child */
 		ATAddCheckConstraint(wqueue, childtab, childrel,
-							 constr, recurse, true, lockmode);
+							 constr, recurse, true, is_readd, lockmode);
 
 		heap_close(childrel, NoLock);
 	}
@@ -7220,6 +7243,10 @@ ATPostAlterTypeParse(char *cmd, List **wqueue, LOCKMODE lockmode)
 	/*
 	 * Attach each generated command to the proper place in the work queue.
 	 * Note this could result in creation of entirely new work-queue entries.
+	 *
+	 * Also note that we have to tweak the command subtypes, because it turns
+	 * out that re-creation of indexes and constraints has to act a bit
+	 * differently from initial creation.
 	 */
 	foreach(list_item, querytree_list)
 	{
@@ -7263,6 +7290,7 @@ ATPostAlterTypeParse(char *cmd, List **wqueue, LOCKMODE lockmode)
 									lappend(tab->subcmds[AT_PASS_OLD_INDEX], cmd);
 								break;
 							case AT_AddConstraint:
+								cmd->subtype = AT_ReAddConstraint;
 								tab->subcmds[AT_PASS_OLD_CONSTR] =
 									lappend(tab->subcmds[AT_PASS_OLD_CONSTR], cmd);
 								break;
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
@@ -1221,7 +1221,9 @@ typedef enum AlterTableType
 	AT_DropInherit,				/* NO INHERIT parent */
 	AT_AddOf,					/* OF <type_name> */
 	AT_DropOf,					/* NOT OF */
-	AT_GenericOptions			/* OPTIONS (...) */
+	AT_GenericOptions,			/* OPTIONS (...) */
+	/* this will be in a more natural position in 9.3: */
+	AT_ReAddConstraint			/* internal to commands/tablecmds.c */
 } AlterTableType;
 
 typedef struct AlterTableCmd	/* one subcommand of an ALTER TABLE */
diff --git a/src/test/regress/expected/alter_table.out b/src/test/regress/expected/alter_table.out
@@ -1538,6 +1538,28 @@ where oid = 'test_storage'::regclass;
  t
 (1 row)
 
+-- ALTER TYPE with a check constraint and a child table (bug before Nov 2012)
+CREATE TABLE test_inh_check (a float check (a > 10.2));
+CREATE TABLE test_inh_check_child() INHERITS(test_inh_check);
+ALTER TABLE test_inh_check ALTER COLUMN a TYPE numeric;
+\d test_inh_check
+Table "public.test_inh_check"
+ Column |  Type   | Modifiers 
+--------+---------+-----------
+ a      | numeric | 
+Check constraints:
+    "test_inh_check_a_check" CHECK (a::double precision > 10.2::double precision)
+Number of child tables: 1 (Use \d+ to list them.)
+
+\d test_inh_check_child
+Table "public.test_inh_check_child"
+ Column |  Type   | Modifiers 
+--------+---------+-----------
+ a      | numeric | 
+Check constraints:
+    "test_inh_check_a_check" CHECK (a::double precision > 10.2::double precision)
+Inherits: test_inh_check
+
 --
 -- lock levels
 --
diff --git a/src/test/regress/sql/alter_table.sql b/src/test/regress/sql/alter_table.sql
@@ -1145,6 +1145,13 @@ select reltoastrelid <> 0 as has_toast_table
 from pg_class
 where oid = 'test_storage'::regclass;
 
+-- ALTER TYPE with a check constraint and a child table (bug before Nov 2012)
+CREATE TABLE test_inh_check (a float check (a > 10.2));
+CREATE TABLE test_inh_check_child() INHERITS(test_inh_check);
+ALTER TABLE test_inh_check ALTER COLUMN a TYPE numeric;
+\d test_inh_check
+\d test_inh_check_child
+
 --
 -- lock levels
 --
